The flow mechanism and thermal transmission are observed by exposing the nanofluid flow through the heated slippery surface. The influences of permeable surface, radiative flux and heat absorption/generation are also elaborated in this study. The flow of nanofluids has been designed using a PDEs system, which are then transformed into a set of ODEs via resemblance modification. The numerical technique “shooting method” is used to solve the acquired nonlinear set of non – dimensional ODEs. The results are physically exemplified through tables and plots. It has been detected that the accumulation of nanomaterials in the engine oil, reduces the skin friction while accelerating the energy transfer rate. The velocity field significantly decelerates with the encouragement of the porosity factor, and volume fraction of NPs. However, the temperature profile significantly escalates with the encouragement of the porosity factor, and volume fraction of NPs.In the present analysis, we study the energy transference through engine oil-based Prandtl–Eyring nanofluid flow through a heated stretching surface. The nanofluid is prepared by adding copper (Cu) and titanium dioxide (TiO In the present analysis, we study the energy transference through engine oil-based Prandtl–Eyring nanofluid flow through a heated stretching surface. Solid particles conduct thermal heat more efficiently than liquids, which is a widely accepted fact. Therefore, the addition of particles of nanoscale size to conventional fluids significantly enhanced their thermal conductivity. Nanoparticles is the name given to these solid particles. A nanofluid is a fluid that consists of both the nanoparticles and base fluid. Eastman2 claimed in an experimental study that a slight quantity of nanoscale solid substantial particles can enhance the thermal conductivity of normal liquids. This research found that adding Cu NPs or carbon nanotubes (CNTs) at 1% enhanced the thermal efficiency of ethylene glycol (the base fluid) by 40–50% (volume fraction). This is due to nanofluids playing an important part in electromechanical devices, advanced cooling systems, heat exchange, and so on. The stimulus of radiant energy on a hydromagnetic unsteady liquid flow through a leaky stretchable sheet with heat and mass conversion was described by Bilal et al.3 The micro-rotation characteristic was discovered to be caused by the permeability factor. Ghasemi et al.4 revealed the influence of magnetic pitch on nanofluid flow across a stretching sheet at the stagnation point. Furthermore, the outcomes revealed that as the Lewis number upsurges, so does the heat flux of the nanofluid. The magnetohydrodynamic water-based NF flow containing motile microorganisms and nanotubes across a porous vertical floating substrate was investigated by Algehyne et al.5 Increasing heat absorption and production rates were thought to increase the rate of energy transference. Investigators6–11 looked into the thermal properties of nanofluids by incorporating multiple types of nanoparticles into the base fluid.Base fluids  play a critical role in transferring heat in industrial operations. In general, the heat transferability of these liquids is poor. To overcome this obstacle, nanoparticles (<100 nm) are inserted to enhance abilities of heat transport. Choi and Eastmanet al.12 exercised an experimental two-step method to create a hybrid nanofluid composed of Al2O3–Cu/water. Madhesh et al.13 conducted experiments on a copper–titania (Cu–TiO2) hybrid nanocomposite and copper–titania (Cu–TiO2) HNF flows with volume fraction ranging from 0.1% to 1.0%. The outcomes discovered that for a volume concentration of up to 1%, the heat flux rate is enhanced by 49%. Toghraie et al.14 carried out a research on the mixture of a ZnO–TiO2/EG HNF to illustrate the influences of nanoparticle temperature and concentration on the conduction of the HNF. The outcomes were intriguing, showing that at 50 degrees Celsius, heat radiation was 32% with a volume fraction of 3.5%. In addition to these experimental efforts, scientists have concentrated on theoretical research of hybrid nanoliquid flows. Gul et al.15 compared Yamada–Ota and Hamilton–Crosser HNF models that contained silicon carbide (SiC) and titanium oxide TiO2 nanoparticles (NPs) in diathermic oil. After being stimulated with a magnetic dipole, the flow of the hybrid nanoliquid was predicted to occur over a larger surface. The key findings indicated that the Yamada–Ota model outperformed the Hamilton–Crosser hybrid nanoliquid flow model in terms of heat transfer efficiency. Arif et al.16 studied theoretically ternary hybrid nanoliquid flow with base liquid water between two parallel sheets with various nanoparticle shapes such as cylinders, spheres, and platelets of carbon nanotubes, aluminium oxide, and graphene, respectively. The unsteady fluid flow and energy transmission of a Cu–Al2O3/water-based HNF over an axially impermeable contracting and extending substrate were investigated by Khan et al.17 A hybrid nanofluid (Cu–Al2O3/water) was discovered to accelerate heat transmission when compared to a conventional fluid. Elattar et al.18 explored the flow of a steady electrically charged HNF through an opaque thin flexible sheet using the computational technique PCM. The influence of velocity index and Hall current raises the velocity contour, while changes in particle volume and sheet thickness lower it. Wang et al.19 inspected the influence of a biochemical reaction on a HNF unsteady flow along a texture that was expanding. The presence of the unsteadiness variable has been observed to regulate the transition from laminar to turbulent flow. Alharbi et al.20 characterised the flow of an energy propagating high conductivity ternary HNF that included nanocrystals as well as an extended sheet. When ternary hybrid NPs are varied the base fluid thermal conductivity is greatly improved. Ahmad et al.21 looked into the heat transport properties of engine oil containing nanoparticles like Cu and TiO2. They found that the effectiveness of copper and titanium oxide in engine oil is overlooked.Recently, hybrid nanofluids (HNF), a more advanced type of nanofluid, have been introduced. The hybrid nanofluids are made up of an ordinary liquid and two or more types of nanoparticles. In terms of heat transport, hybrid nanofluids outperform conventional nanofluids. Suresh et al.22 described visco-inelastic liquid flow boundary layer similarity solutions. Hayat et al.23 inspected the consequence of magnetohydrodynamics on the flow of a peristaltic dissipative Prandtl–Eyring liquid. According to the results, Akbar24 discovered the convective boundary constraints of Prandtl–Eyring liquid flow with peristatic properties. Khan et al.25 conducted a mathematical computational evaluation of bio convection on PEF. The effects of thermo/phonetic force and Brownian motion on electrically conducting PEF generated by strained shallow were investigated by Abdelmalek et al.26Prandtl–Eyring nanofluid is a mixed convection flow of nanoparticles with activation energy that is non-linear. As a result, numerous non-Newtonian fluid models have been offered in the literature. The Prandtl–Eyring fluid is one of them. Darji 27–29 Heat transfer is a well-established phenomenon that happens as a consequence of temperature variations between two distinct objects or between components of an identical system. For decades, Fourier's30 fundamental law of heat conduction, has been used to measure heat transfer properties. Later, with concern, it was discovered that this model produces a parabolic energy equation with an initial disruption that lasts across the process. A “paradox of heat conduction” denotes this weakness in the Fourier model. Cattaneo31 addresses this flaw by incorporating a relaxation term into the Fourier approach. Afterward, Christov32 created the Cattaneo-suggested relationship with the Oldroyd upper-convected variant via frame-indifferent alteration. This type of relationship is identified as the Cattaneo–Christov (CC) flux model. Kumar et al.33 used a CC flux model to investigate the features of Dusty fluid of dissolved HNF flows in two phases through an elongated cylinder. The shooting approach with RK–Fehlberg system, were used for numerical results. Ramzan et al.34 used the CC model and MHD impact with heterogeneous reactions adjacent to a stagnation point to calculate the Williamson fluid flow. It should be acknowledged that the fluid parameter has a diametrically opposed influence on velocity and temperature profiles. Shah et al.35 used the CC model to investigate heat transfer in a 2D  flow of Ree–Eyring nanoliquid through a stretching sheet.Because of the numerous implementations in nanofluid mechanics, investigators are developing a wave-based heat transfer methodology rather than a diffusion operation.2 nanoparticles are added to engine oil to create the nanofluid. The nanofluid flow was modelled as a system of PDEs, which are then transformed into a set of ODEs via resemblance modification. The numerical technique “shooting method” is used to solve the acquired nonlinear set of non – dimensional ODEs. Local velocity gradient and Nusselt number statistics are estimated and analysed. Despite the fact that the phenomena described in this manuscript have never been attempted before.The primary goal of this research is to determine how heat absorption and thermal radiation, as well as viscous dissipation and energy transportation, occur in engine oil-based NF flow over a heated elongating surface. Cu and TiO2., where b is a stretching rate as shown in x = 0 the surface is heated with relation  where b* and Tw represents the energy variation, surrounding temperature and surface heat, respectively. The surface of the plate is supposed to be slippery.We have assumed the 2D viscous dissipative nanofluid flow over an irregular moving horizontal porous plate. The plate is moving with velocity 2.1.The fluid flow model is displayed in 2.2.33–35 for the nanofluid flow in a porous medium and heat equation with variable temperature, thermal radiation, Cattaneo–Christov heat flux model, and heat source/sink utilizing the approximate boundary-layer are:The constitutive Prandtl–Eyring model21v, and u are the velocity components, α1 and C1 are the fluid parameters, μnf is the dynamic viscosity of nanofluid, ρnf is the density, knf is the thermal conductivity, Q0 is the heat source, hf is the heat transition constant and K is the surface permeability, ΩE is the heat flux for which model equations isBoundary conditionsThe varying thermal conductivity is classified as:2.3.ρff) is related to the density of the fluid (ρf) and that of the solid nanoparticle phase (ρs) as follows:35ϕ is the volume fraction of NPs. Similarly the volume specific heats are correlated as:Different researchers presented mathematical models that explain the effective characteristics of heat transfer in the nanofluids. These models present physical characteristic of the nanofluid in term of relevant physical characteristics of the solid nanoparticles and base fluid. The density of a ferrofluid  model can be utilized:2) nanoparticles (NPs) to the base fluid engine oil has been achieved into the account the characteristics using in In the present study heat transfer analysis through copper (Cu) and titanium dioxide  versus fluid parameters A & β, porosity parameter β0, velocity slip parameter Λ, volume fraction parameter ϕ, and suction parameter S. A on fluid velocity while the other parameters are held constant. This graph shows that increasing the value of A causes an upsurge in the value of velocity. Because higher values of A tend to reduce viscosity, which overwhelms the resistance offered by the liquid. β increases. It is physically true because β varies inverse proportion with momentum diffusivity, resulting in a decrease in velocity gradient. β0 on the velocity distribution. The velocity decreases as β0 increases. Physically, the existence of a porous medium has increased the medium's opposition to fluid flow. ϕ affects the velocity profile f′(η). When the particle volume ϕ fraction is risen, the velocity profile f′(η) reduces. As the volume fraction ϕ of the nanoparticles grows, the fluid thickens, and a conflicting force develops, leading to deceleration. f′(η) as a function of the velocity slip parameter Λ. In general, Λ calculates the amount of slip at the cylinder's surface. Here, we examine how fluid velocity decreases as Λ increases. It is because Λ primarily reduce speed of fluid motion, confirming a reduction in net movement of fluid molecules. Because there is less molecular progression, velocity fields decline. S. Suction is an efficient method for preventing boundary layer separation, as well as controlling velocity and heat energy. The amount of fluid particles is close to the wall after reaching the maximum value of the suction/blowing parameter. Accordingly, the outline of the associated boundary layer becomes thinner over time, and the velocity profiles decelerate as S strength increases.6.2.θ(η) versus the thermal relaxation parameter δe, volume fraction parameter ϕ, Biot number Bζ, heat generation constraint Q, thermal radiation term Rd and Eckert number Ec. δe increases. It is also observed that the thickness of the thermal boundary layer diminutions. This is due to the fact that as δe intensifies, the material particles necessitate more time to transferal heat to their neighbouring droplets. To put it another way, for advanced values of the δe parameter, the material reveals a non-conducting property, which contributes to a narrower temperature distribution. ϕ. Because of the collision of tiny nanoparticles in the flow field produces thermal energy, which advances the temperature of the fluid. Therefore, the addition of Cu and titanium NPs enhances the energy propagation θ(η). Bζ on the energy profile. The Biot number is related to the surface's convective boundary constraints. As βζ boosts, so does the temperature profile close to the surface, raising the temperature close to the surface and, consequently, the thickness of the thermal boundary layer, as realized in Q on fluid temperature. The temperature profile is seen to boost as Q goes up. Heat is generated in the flow regime as a result of positive modifications in the heat generation parameter, causing a rise in fluid temperature.7.CfRex1/2 and Nusselt number NuRex−1/2versus different physical entities. It has been perceived that the accumulation of NPs to the engine oil, accelerates the skin friction, while reducing the energy transfer rate. Where, the fluid parameter β boost the skin friction, while the variation of porosity parameter dimmish the skin friction as observed in 8.2 NPs in the engine oil. The flow of nanofluids has been designed using a PDEs system, which are then transformed into a set of ODEs via resemblance modification. The numerical technique “shooting method” is used to solve the acquired nonlinear set of non – dimensional ODEs. The outcomes are physically exemplified through figures and tables. The key findings are:We analyzed the energy transference and entropy generation through nanofluid flow through a heated extending surface. The nanofluid is organized by the accumulation of Cu and TiOf′(η) significantly improves with the influence of parameters A, while declining with the effects of parameter β, suction parameter S, slip parameter Λ, porosity factor, and volume fraction of nanoparticles.• The velocity θ(η) curve boosts with growing values of the thermal relaxation coefficient δe and volume fraction parameter ϕ.• The temperature θ(η) pointedly boosts with the stimulus of Q, Eckert number Ec, and thermal radiation parameter Rd.• The temperature • The accumulation of nanomaterials in the engine oil, speeding up the skin friction, while reduces the energy transfer rate.β boost the skin friction, while the variant in porosity parameter dimmish the skin friction.• The fluid parameter • The rising quantity of thermal relaxation parameter, Eckert number and thermal radiation declined the energy transmission rate.BrBrinkman numberCpSpecific heat transfer (J/Kg/K)cbDrag forceEcEckert numberhfHeat transition constantKPermeability of porous mediumk−1 K−1)Thermal conductivity Velocity components α1, C1Fluid parameterA, βDimensionless fluid parameterβ0Porosity parameterβζBiot numberΛVelocity slip parameterδeThermal relaxation parameterϕVolume fraction parameterεTemperature dependent thermal conductivity parameterηIndependent coordinateνKinematic viscosityμDynamic viscosityρ−3)Density (kg mρCpHeat capacitanceψ2 s−1)Stream function (mfBase fluidsSolid nanoparticlenfNanoparticleswWall∞Free-streamThe data that support the findings of this study are available from the corresponding author upon reasonable request.All authors have equal contributions.The authors declare that they have no competing interests.


The analyticalpredictions are confirmed using numerical simulations.The development of flexible and lightweight electromagneticinterference(EMI)-shielding materials and microwave absorbers requires precisecontrol and optimization of core–shell constituents withincomposite materials. Here, a theoretical model is proposed to predictthe static and dynamic properties of multilayered core–shellparticles comprised of exchange-coupled layers, as in the case ofa spherical iron core coupled to an oxide shell across a spacer layer.The theory of exchange resonance in homogeneous spheres is shown tobe a limiting special case of this more general theory. Nucleationof magnetization reversal occurs through either quasi-uniform or curlingmagnetization processes in core–shell particles, where a purelyhomogeneous magnetization configuration is forbidden by the multilayeredmorphology. The energy is minimized through mixing of modes for specificinterface conditions, leading to many inhomogeneous solutions, whichgrow as 2 Core–shellparticles inherit the traits of both the core and surrounding shell,which results in enhanced surface properties that are not presentwhen only a single material is utilized.13 By precisely controlling the layer thickness andinterlayer coupling,16 it is possible to enhance the properties of core–shellparticles for both existing and prospective applications. Hence, anin-depth understanding of the behavior of core–shell constituentswithin composite materials is key to achieving technological applications.Magnetic particles have attracted broad attention for a vast numberof applications such as impedance matching and antenna miniaturization19 in addition to targeted destruction of cancer cells.22 In the latter case, it is crucial to achieve repeatability of themagnetization reversal mechanism as this determines the heating performanceof the core–shell system during the hysteresis cycle.26 In the gigahertz frequency regime, exchange modes have drawn significantinterest for the development of efficient microwave absorbers.31 Exchange modes are known to occur at frequencies above the uniformferromagnetic resonance and provide a potential avenue to achieveimpedance matching between magnetic/dielectric layers and to broadenelectromagnetic wave absorption at high frequencies.33Monodisperse core–shell particlespossessing exchange-coupledmagnetic layers have attracted considerable interest in recent decades,as the performance of microwave absorbers,35 increasing attentionhas been directed toward three-dimensional magnetic geometries, suchas spherical particles,36 helices,38 torus,41 and the Möbius ring,42 as they provide new topological mechanisms for controlling magneticproperties at the nanoscale.44 Recent analytical studiesof spherical shells have focused on curvature-induced magnetizationtextures and skyrmions,45 phase transitions,46 and magnetic resonance,49 where the shellis usually placed in contact with a vacuum at the outer/inner surfaces.However, for practical applications to be realized, it is also importantto consider the static and dynamic behavior of magnetic shells whenthey are directly coupled to neighboring materials across a nonmagneticinterface.However, precise control and prediction of the static anddynamicmagnetic properties of multilayered particles remain a challenge dueto their dependence on compositional structure, surface coatings,and interlayer coupling. Although most devices exploiting multilayeredeffects rely on thin films,n, where n is the number of magnetic layers.The results can be computed quickly for an arbitrary number of exchange-coupledmagnetic layers of finite thickness, in contrast to numerical investigations,which suffer rapid growth of adjustable input parameters with increasinglayers, leading to prohibitively expensive computation time. Moreover,it is possible to study interface and surface coating effects analyticallywithout relying on the concept of phenomenological surface anisotropy.Finally, the analytical predictions are confirmed using numericalsimulations.In this letter, the theoretical results for nucleationand exchangeresonance in homogeneous spheres are generalized to an arbitrary numberof exchange-coupled magnetic layers separated by nonmagnetic interfaces.It is shown that homogeneous reversal is generally forbidden in sphericalcore–shell particles. The critical sizes for transitions fromcurling to quasi-uniform behavior are calculated, and the number ofmixed nucleation modes is shown to scale as 2H be applied along the z axis, which isalso assumed to be an easy axis for magnetocrystalline anisotropyenergy and can be either cubic or uniaxial. For this system, the nucleationof magnetization reversal is described by the linearized differentialequation50m(r) is a small transverse variation of themagnetization, Ms is the saturation magnetization, C and K are the local exchange and anisotropyconstants, H is the applied field, and Nz is the demagnetizing factor along thedirection of saturation. U(r) represents the scalar potential created by the transversemagnetization distribution m(r) and is described by the magnetostatic PoissonequationConsider a spherical particle comprisedof ferro- or ferrimagnetic material and let the external field U(r) = NMsm(r), and the system of equations isreadily solved to give Hd = −4πMs/3. Although the demagnetizing field for aquasi-uniform magnetization state does not simplify in the same way,we can nevertheless treat it as a perturbation of uniform magnetizationand obtain an approximate solution51m(r) ∝ j0(μr/R1). In the limit of a purely homogeneousconfiguration m(r) → const(μ → 0), the perturbation reducesto the transverse demagnetizing factor of an ideally saturated sphere HDeff = −4πMs/3. The perturbativecorrection to curling nucleation m(r) ∝ j1(μr/R1) vanishesdue to the flux closure.Two eigenmodes are of interest in thepresent context of core–shell particles, namely, curling anda quasi-coherent rotation mode, where coherent (Stoner–Wohlfarth)rotation is found to be forbidden. For reversal by the curling mode,the transverse demagnetizing field can be written in the closed formas ∇⃗r =0 is52m represents the azimuthal component of the magnetization,μ are the eigenvalues, R1 is theradius of the core and R2 is the radiusof an inner magnetic shell, each shown in R3 is theouter radius of an additional outer magnetic shell. j and y are spherical Bessel functions of the firstand second kind, respectively, and Bi are arbitrary integration constants. The physicalform of the solution depends on the specific material, geometric,and interfacial parameters. When the eigenvalues have complex solutions,the spherical Bessel functions are replaced with their modified forms In and Kn, which represent localized decaying modes.Substituting the solutions ζ –β1]δ, F = −[(A12 – β12)/ζ +β2]δ,and ζ = M2/M1. The interlayer exchange coupling can have different origins,including Ruderman–Kittel–Kasuya–Yosida (RKKY)interactions. The exchange and magnetocrystalline anisotropy energydensities are denoted by α = C/2Ms2 and β= K/Ms2, respectively. A12 = ξAint,s/(Mint2 δ)is a parameter of uniform exchange interaction, where Aint,s denotes the effective surface exchange constantof the interface Aint,s = Aint/δ with Aint beingthe exchange constant of the interface region and δ the interfacethickness. Mint is the effective saturationmagnetization of the interface and ξ is a proportionality constant,which can be derived in principle from ab initio calculations. Theparameter β12 = K12/Mint,s2 is an anisotropy parameter, where K12 is the uniaxial magnetic anisotropy at the interface. Although theparticle has been physically divided into multiple layers, the continuityof the effective magnetization across the exchange-coupled interfacepreserves the overall spherical shape of the particle from a mathematicalpoint of view. The physical interpretation of D and F is that of effective material properties obtained by averagingover the finite thickness δ of the interface. If the inner shellis exchange-coupled directly to an additional outer shell at the interface r = R2, then continuity of themagnetization across this interface leads to another equationwhere C2(∂ m2)/∂ n = C3(∂ m3)/∂ n55 of the magnetization at the coupled inner–outershell interfacemust also be continuous at r = R2, hence2R2/R1 and τ= μ3R2/R1. Finally, at the outer surface of the outer shell, theusual boundary condition for free surface spins is chosen ∂ m/∂ n = 0, yielding3R3/R1. Nontrivialsolutions satisfying these B1–5 vanishes.This determinant can be solved with the three expressions .The most general solution of this systemof equations is59 The electromagnetic fields arecomputed from Maxwell’s curl equationsH is themagnetic field, E is the electric field,ε is the permittivity, σ is the electrical conductivity,and t is the time. The magnetic flux density B is coupled to the magnetization M through the constitutive relation B = μ0(M + H), where μ0 isthe permeability of free space. The magnetization is evaluated fromthe solution of the Landau–Lifshitz–Gilbert equation(LLG)11μ0 (m·Hz·A–1) is thegyromagnetic ratio, α is the phenomenological Gilbert dampingcoefficient, and |M| = Ms is the saturation magnetization. To achieve rapid convergenceduring static calculations, the conductivity is artificially increasedto accelerate the damping of the electric fields. The effective field Heff in To investigate finite magneticobjects, coupled electromagnetic–micromagnetic simulationswere performed.H is the Maxwell field evaluated from the solution of Hκ = −gMzZ describes the uniaxialanisotropy along the z axis, where g = 2K1/μ0Ms2 and K1 is the anisotropy constant. Hex in 2 is the Laplacianoperator. The parameters used in the simulations are taken from Table S1.where 60 Vortex configurations, which are typically foundin larger particles, have shown enhanced specific absorption rate(SAR) values as they reduce stray fields and diminish the formationof aggregates. Stabilization of such configurations down to smallersizes is therefore desirable from the point of view of minimizingagglomeration and improving heating efficiency.Recent work has shown that exchange-coupledcore–shell particlesexhibit mixed reversal processes with uniform-like or vortex-likemagnetic configurations emerging depending on the specific material,geometric, and interfacial properties of the particle.80Ni20 core is coupled to a Fe14Co43Ni43 shell on the surface, the curling mode in the core can be stabilizeddown to significantly smaller sizes, as shown by the growing regionof “C–QU” with decreasing R1/R2. It can be confirmed by substitutionthat the multilayered structure prevents the formation of a purelyuniform magnetization configuration because the constant function = const) does notsimultaneously satisfy -shielding materials and microwave absorbers basedon core–shell constituents.


Phragmites) collected from ancient Great Wall fascines in today’s Gansu and Xinjiang using a combination of chromatographic techniques and isotope analyses. Our molecular data, along with Scanning Electron Microscopy, demonstrate excellent preservation of these ancient reeds, which were harvested from nearby habitats during periods of significant expansion of Imperial China when climate conditions sustained sizeable oases in the region. Stable isotope data capture differential rates of environmental change along the eastern margin of the Tarim Basin since the Han Dynasty (170 BC), implying that significant surface-water hydrological changes occurred only after the Song Dynasty (1160 AD) due to regional climate change. This study reveals the wealth of environmental and climate information obtainable from these site-specific organic building materials and establishes the foundation for further applications of advanced molecular, biochemical, and isotopic technologies to study these common and widely-distributed organic archaeological materials.Plant materials used in the construction of segments and beacon towers of the ancient Great Wall in northwestern China contain untapped potential for revealing local paleoclimatic and environmental conditions. For the first time, we characterize the molecular preservation and stable carbon and nitrogen isotope compositions of AMS-dated common reeds ( What is perhaps less well known, however, is that the iconic brick and stone walls built during the Ming Dynasty in the 15th century AD2, are only part of a series of multi-material fortifications that stretch across northern China from Hebei Province to Xinjiang Uyghur Autonomous Region , were constructed using locally available materials, with reed fascines and wood bundles interbedded with gravel-mixed rammed earth 10.As one of the most recognizable world heritage sites, the Great Wall of China is a manifestation of the engineering capabilities and architectural achievements of multiple Chinese dynastiesion Fig. 1,3–7. Wa14, isolated beacon towers , the cosmopolitan common reed, being the most conventional genus used in fascines as natural building material  Trin. ex Steud.22, reports on pollen23 and phytoliths24 of Phragmites in archaeological contexts, and the identification of a rope made from culms (stems) of Phragmites at the Gumugou Cemetery, a site dated to 3800 years cal BP and ~ 70 km east of Lop Nur25, no molecular characterization or isotope measurements have been taken on the ancient remains of Phragmites collected directly from the Great Wall itself.In the vast arid regions of central Asia, human livelihood is ultimately dependent on oases that supply freshwater to sustain both natural vegetation and agricultural cropsial Fig. . Phragmi27  ecological subtleties that would have existed at various locations along oases in otherwise arid northwestern China when ancient Great Wall segments were built. In fact, there are no on-site paleoenvironmental reconstructions from northwestern China that speak directly to the creation and maintenance of altered ecosystems by the Han or later dynasties.Extensive lacustrinen-alkanes and measure bulk carbon (δ13C) and nitrogen (δ15N) isotope ratios of accelerator mass spectrometry (AMS) dated Phragmites sampled directly from 13 Great Wall sections or beacon towers constructed during the Han, Jin, Tang, or Song Dynasties in today’s Gansu and Xinjiang. Our on-site data provide novel evidence for the source and diversity of reeds used in Great Wall building activities. We compare the ancient data with biochemical information obtained from modern P. australis available from the study area to reveal climatic and environmental dynamics during early Chinese historical periods with a focus on the rate, timing, and cause of hydrological changes. Biomolecular analyses of these organic materials preserved within ramparts may provide direct evidence of climatic and environmental conditions at specific historical points along the Great Wall. This study also highlights the future potential of these in situ material as valuable biogeochemical archives for studying human-altered ecosystems and hydrology.Here, we characterize the molecular preservation and distribution of plant wax 51. Finally, and somewhat surprisingly, the Sishilidadun Beacon Tower (Site 14) dates to the Song Dynasty, 1030–1160 AD, when the eastern Tarim Basin was governed by the Western Liao Dynasty.To constrain the chronology of each sampling location, we obtained eight AMS radiocarbon ages from four sites Table ”. We det28. The Yingpan City Buddha Tower and Burial Site (Site 9) was radiocarbon dated to a median age probability of 305 AD in the Jin Dynasty52, consistent with the funerary artifacts found in the Yingpan cemetery53. Due to similar archaeological contents found in burials55, the nearby Yingpan City Heritage Site (Site 10) is assigned to the Jin Dynasty as well, although it is likely that Yingpan City was continuously occupied since the Han Dynasty. Finally, we attribute the Tahaqi Beacon Tower (Site 13), to the Song Dynasty period due to its proximity and similar style of construction to Sishilidadun.Other sampling locations were previously dated. The Milan Castle Heritage Site (Site 8) was constructed during the Tang Dynasty and radiometrically dated to ~ 770 ADPhragmites culms (n = 6) consistently exhibit excellent molecular preservation with abundant labile biomolecules  and stearic (C18) acids, but dodecanoic (C12) and tetradecanoic (C13) acids were identified in one modern P. australis leaf collected near Yumenguan (Site 5). Indoles  indicate the presence of amino acids in modern P. australis samples. There are some variations in compound distribution among ancient samples collected from different sites  in ancient culms is approximately 12-times lower than that of modern samples (Data n = 38) per gram of dry material (μg/g) compared to the 4163 to 32,296 μg/g  measured in modern plants. Overall, there is a significant difference in C21–C33n-alkane abundance between modern and ancient samples as shown by a Student’s t-test  and Mann–Whitney U test (p = < 0.0001).Culms from ancient wall segments or beacon towers have wider les Data , having n-alkanes in Great Wall samples is expected given their antiquity. However, the carbon preference index of the C21–C33n-alkanes (CPIC21–C33), a metric used to examine the odd-over-even carbon number predominance and as an indicator for hydrocarbon maturity58, indicates that no significant degradation occurred among the longer chain n-alkanes from ancient samples. Both modern and ancient CPIC21–C33 values are ≥ 2.0  and Mann–Whitney U test (p = 0.827). Like lignin and polysaccharide, lipid preservation is contingent on the dry regional climate which likely facilitated the preservation of these organic archaeological remains over time62.The lower concentration of 2.0 Fig. , which i27, C29, and C31 relative abundances for n-alkanes from ancient Phragmites and modern P. australis. The wider chain-length distribution of n-alkanes in ancient reeds contrast with those of modern samples, suggesting that ancient Phragmites used in the construction of the Great Wall were harvested from habitats that were likely more diverse and growing under cooler and wetter climate conditions relative to today, as chain-length distribution in P. australis has been shown to be a function of temperature and water availability63. Of the 33 ancient samples containing enough lipid material for GC-FID analysis, 13 (39.4%) have C27 as the most dominant n-alkane, while C29 and C31 are most abundant in 9 (27.2%) and 8 (24.2%) samples, respectively. The sample from Sishilidadun has C21 as the most dominant compound. This wider n-alkane distribution contrasts with modern reeds where 9 of the 12 samples (75%) have the C29 homologue as the most dominant compound, while only 2 (16%) samples from Sishilidadun have C27 as the most abundant alkane, and 1 sample (8%) from Yumenguan has C31  for Han and Tang aged reeds overlap with the distribution of modern ACL21–33 values  and Mann–Whitney U test (p = 0.616), ACL21–33 tracks higher in all modern samples from individual sites where both were sampled, except Majuanwan , while modern bulk δ13C values, corrected for the Suess effect, range between − 24.6 and − 20.8‰  , Jin (Sites 9 and 10), Tang , and Song (Site 14) samples yield bulk δ, Jin (Si12) Fig. .Figure 713C signatures of modern P. australis samples. Modern samples exhibit significant differences in δ13C values between samples from eastern (n = 7) and western (n = 5) sites  is 0.5‰ heavier than western  samples  is 2.7‰ heavier on average than Jin Dynasty Great Wall culms from the site, while modern samples from the Sishilidadun Beacon Tower of the Song Dynasty (Site 14) are on average 2.8‰ higher than ancient reeds from this location.This 2.5‰ heavier δNur Fig. . Thus, t15N, with values ranging from 0.8 to 33.5‰ . Extremely heavy δ15N values were obtained in samples from the Tang Dynasty Milan Castle Heritage Site  and in the Song Sishilidadun Tower . In general, δ15N values in Han  and Jin  era samples are significantly different from Tang  and Song  aged samples  δ15N values from Xinjiang76, indicating that human activities such as crop fertilizing, in addition to climatic parameters, may have elevated δ15N values at these locations.Ancient reed samples yield large variations in bulk δdun Data . This ma15N value of 27.5 ± 6.0‰, which is about 12‰ heavier than that of Sishilidadun. The 15.9 ± 4.0‰ δ15N from ancient Sishilidadun stands in exceptional contrast to the modern 0.24 ± 0.04‰ value obtained from extant P. australis growing at the site. The only other modern δ15N value obtained, 13.4‰, comes from the Yingpan City Heritage Site (Site 10). As for other ancient samples, the Cang Ting Sui Beacon Tower (Site 5) and wall segments at the Great Wall Heritage Site (Site 6), locations which are only 5 km apart, have mean δ15N values of 8.3‰ and 2.0‰, respectively, showing the large variability and local variations between sites , the local differences in δ15N more likely reflect the use of fertilizers around large population centers in the past, which would have resulted in potential agricultural runoff that drove δ15N values higher in wild reeds that were then harvested for wall building. Fertilizers derived from manures or guano are enriched in 15N and have a significant impact on plant nitrogen isotopic values79.The culms used for the construction of the Milan Castle yield an exceptionally high mean δ14 , one of the northern-most beacon towers along the Kongque River, suggests that wall-building activities lasted into the post-Tang era and may have been a defensive practice adopted by nearby states like the Qocho Uyghur Kingdom or imported from northeastern China when the Western Liao Dynasty was established in Central Asia. Nevertheless, our new radiometric dates shed light onto the previously conflicting archaeological age uncertainties for these ancient structures.The different ages obtained from the Xinjiang beacon towers are somewhat surprising. On the one hand, the Tang aged material from Sites 11 and 12 confirm recent archaeological findings from a nearby towern-alkane data demonstrate the exceptional preservation of the ancient reeds used in Great Wall construction, despite the lower quantity of certain biomolecules in archaeological samples. Desiccation enhances preservation for plant material at both structural and molecular levels62, so it is expected that the dry climate of northwestern China helped facilitate the longevity of ancient reeds protected within wall ramparts. The excellent molecular preservation of these ancient reeds is confirmed with SEM observations , and from the site’s modern P. australis δ15N value of 13.4‰. The δ15N data from Yingpan City would therefore suggest that local Phragmites were not purposely fertilized here, nor did they grow in an area influenced by agricultural runoff. Though we are currently unable to determine whether Phragmites used in the construction of Milan Castle were purposely fertilized and deliberately managed for wall construction, or had naturally collected nutrients from agricultural runoff, the extremely high value here compared to sites like Yingpan City suggests that the possible manuring hypothesis deserves further investigation.The extremely high δ80. However, the uniformity in our ancient Phragmites δ13C values indicates that surface-water availability, and the extent of oases, was more homogenous from the Han through Song Dynasties across both sides of Lop Nur , identified only to the genus level, were sampled from exposed fascines of remnant wall segments, beacon towers, or fortification ruins  and leaves (n = 4) belonging to the species P. australis were sampled directly from wild plants growing in the study area  that were cut with single-edged blades. The external and internal surfaces of these pieces were then coated with a 15 nm thin film of gold and observed using a JEOL JSM-IT200 Scanning Electron Microscope under low vacuum at 15kv.Scanning Electron Microscopy (SEM) was performed on culm pieces of both modern P. australis from Chinese public land guided by Chinese colleagues with permission granted by their respective research institutes in accordance with relevant guidelines and regulations. This species is not considered at Risk of Extinction and is listed as Least Concern by the IUCN Council, thus, no special permission or license was required for collection100. All collected specimens were identified by Dr. Qin Leng and voucher specimens (see sample ID numbers in Data We only collected samples from wild 14C yr B.P.) by IntCal20 using the OxCal v. 4.2.3 software at 95% probability or 2 standard deviations (2σ) , confirming its Han Dynasty age  is radiometrically dated to ~ 770 AD and was constructed during the Tang Dynasty52. A wall section from the Yingpan City Heritage Site (Site 10) was previously assigned to both the Han and Jin Dynasty based upon burials and associated archaeology55. We attribute Sites 9 and 10 to the Jin Dynasty as Yingpan was likely built during the Han and continuously occupied through the Jin period.The Buddha Tower at the Yingpan City Heritage Site (Site 9) was radiocarbon dated to 305 AD, placing it in the Jin DynastyThe Sishilidadun Beacon Tower (Site 14) is the youngest of the sites studied, as we obtained two AMS ages with radiometric dates of 1030 and 1160 AD. These dates indicate that the structure was built during the Song Dynasty (960–1279 AD), although Song political borders are not known to have extended into the Tarim Basin.The ages for sampling sites in Xinjiang  are grouped into three categories in terms of their chronology . Morphologically, the culms of ancient reeds are indistinguishable from their modern counterparts  and ancient (n = 6) plant samples were analyzed using Py-GC-MS to test for the molecular distributions and preservation of organic compounds at Bryant University, Smithfield, Rhode Island. Samples were pyrolized using a CDS 5250 Pyroprobe by combusting at 610 °C for 20 s to convert macromolecular compounds to GC amenable products. Compound detection and identification were performed using an Agilent 7890A GC System equipped with a Thermo TR-1 capillary column  coupled to a 5975C Series Mass Selective Detector (MSD). The GC oven was programmed from 40 °C (5 min hold) to 100 °C at 10 °C/min, then to 300 °C at 6 °C/min (25 min hold). Helium was the carrier gas with a constant flow of 1.1 mL/min. The MS source was operated at 250 °C with 70 eV ionization energy in the electron ionization (EI) mode and the MS Quadrupole mass analyzer was set to 150 °C with a scan rate of m/z 50–500. Samples were held at the pyroprobe interface for at least 5 min at 300 °C for additional thermal extraction and to remove volatile impurities before gas chromatography. Compounds were identified by comparing their spectra with those reported in the literature104. Duplicate analyses of each sample were conducted for analytical consistency.Modern , and a Flame Ionization Detector (FID). Samples were injected in split mode (split ratio 4:1) and the GC oven was programmed from 40 °C (1 min hold) to 150 °C at 10 °C/min, then to 315 °C at 6 °C/min (20 min hold). Helium was the carrier gas with a constant flow of 1.2 mL/min. Sample peak areas were compared with an external standard mixture  for compound identification and quantification. Specifically, sample n-alkane GC-FID peak areas (PA) were converted to concentrations assuming that the response of each compound is identical to that of the standard mixture (approximately 3–5 PA/ng). A calibration curve was not necessary as the range of n-alkanes measured were not outside the standard carbon homologue range.Plant culms and leaves were lyophilized and ground, then extracted with Dichloromethane:Methanol  using ultrasonication at 40 °C in three, 30-min cycles at the Institute of Earth Environment, Chinese Academy of Sciences, Xi’an. The total lipid extracts were dried under nitrogen and separated into two fractions through silica gel column chromatography using hexane and methanol, respectively, with 27–C35n-alkanes) are most abundant in terrestrial plants106, while submerged and floating aquatic macrophytes contain more mid-chain compounds 108, and short-chains  are dominant in algae110. The average chain length, or the weight-averaged number of carbon homologues of the odd-numbered C21–C33n-alkanes, is used (cautiously) as both biosynthetic source and climate proxies and was calculated as follows:x is the abundance of the chain length with x carbons. The carbon preference index (CPI) examines the odd-over-even carbon number predominance of hydrocarbons and distinguishes sedimentary organic matter deriving from terrestrial plants and that from bacterial or petroleum sources113, and as an indicator for hydrocarbon maturity58. Alkanes deriving from land plants display carbon chains typically (60.7%) with CPI > 5, but have been shown to range between 1 and 99, with most (81.2%) plants having values > 259. Samples containing petrogenic and marine inputs or mature/degraded samples are characterized by considerably lower CPI values of ≤ 1. CPI was calculated using the abundances of odd and even chain lengths from C21 to C33 with the following formula:Generally, long-chains  was analyzed between every twelve samples. The precision of repeated measurements of the laboratory standard was < 0.1‰. Sample carbon isotope ratios (δ13C) are expressed as parts per thousand (‰) relative to the international VPDB standard and defined by the following equation:Culms from modern and ancient reeds were washed with distilled water and treated with 2 M HCl for 24 h at room temperature to remove any potential carbonates before combustion  in a vacuum-sealed quartz tube in the presence of Ag foil and CuO. The purified CO13C values were compared, + 1.9‰ was added to all modern values116  and an international isotope reference material  to control the analytical accuracy of the EA-IRMS. Repeated analyses of the laboratory soil standards with confirmed δ15N values were performed daily to ensure instrumental accuracy. The standard deviation for repeated sample analyses was better than 0.3‰. The δ15N of each sample is expressed as ‰ relative to the international AIR standard and defined by the following equation:The nitrogen isotope ratios of the dried plant samples were determined at the Stable Isotope Biogeochemistry Laboratory at the Institute of Earth Environment, Chinese Academy of Sciences using a FLASH EA1112 elemental analyzer interfaced with a Delta-Plus continuous-flow isotope ratio mass spectrometer (IRMS). All the δU tests were used to test the significance in differences between sample sets using an Alpha (α) of 0.05 (see Tables U tests were run using PAST 4.03 (additional nonparametric statistical tests, Kruskal–Wallis and Spearman’s rank, were also used to test significance in differences between sample sets and are presented in the Finally, two-tailed Student’s t-tests, assuming unequal variances, and Mann–Whitney Supplementary Information 1.Supplementary Information 2.Supplementary Information 3.


Dynamic polarization control is crucial for emerging highly integrated photonic systems with diverse metasurfaces being explored for its realization, but efficient, fast, and broadband operation remains a cumbersome challenge. While efficient optical metasurfaces (OMSs) involving liquid crystals suffer from inherently slow responses, other OMS realizations are limited either in the operating wavelength range (due to resonances involved) or in the range of birefringence tuning. Capitalizing on our development of piezoelectric micro-electro-mechanical system (MEMS) based dynamic OMSs, we demonstrate reflective MEMS-OMS dynamic wave plates (DWPs) with high polarization conversion efficiencies (∼75%), broadband operation (∼100 nm near the operating wavelength of 800 nm), fast responses (<0.4 milliseconds) and full-range birefringence control that enables completely encircling the Poincaré sphere along trajectories determined by the incident light polarization and DWP orientation. Demonstrated complete electrical control over light polarization opens new avenues in further integration and miniaturization of optical networks and systems. Dynamic polarization control is crucial for intelligent optical systems, from imaging to sensing. The authors demonstrate efficient and broadband MEMS-based dynamic optical metasurface wave plates with full-range and fast birefringence tunability. Plentiful dynamic OMSs have been demonstrated in the past decade, implementing active amplitude and phase modulation with diversified functionalities10. Despite significant progress achieved in dynamic control of amplitude and phase responses, OMS-enabled active polarization control in the optical range remains largely unexplored. At the same time, the polarization of light is crucial for the realization of adaptive integrated photonic systems due to the fundamental role of polarization as another intrinsic characteristic of optical waves, which is uncorrelated with the amplitude and phase. To implement active polarization control with dynamic OMSs, one should be able to dynamically tune the OMS optical anisotropy in a wide range. The corresponding OMS realizations rely on the birefringence property of natural materials12 or metasurfaces18, consisting of anisotropic meta-atoms. In either case, since available OMS thickness  and birefringence are limited, identification of a suitable OMS configuration is a rather complicated and arduous issue, with the outcome exhibiting drawbacks, such as slow responses, narrow bandwidths, limited dynamic ranges of birefringence, and low polarization conversion efficiencies  for two orthogonal linear polarizations (LPs) can be realized for the operation wavelength λ = 800 nm at a specific air gap of Ta = 400 nm for OMS nanobricks with sufficiently large aspect ratios , resulting in our choice of the nanobrick long side length Lu = 200 nm due to the electron-beam lithography (EBL) fabrication (aspect ratio) constraints. The short side length Lv is determined by maximizing reflection amplitudes for both orthogonal polarizations  expected at all air gaps Ta along with ensuring the full-range birefringence control , phases , and birefringence (Δϕvu), when changing the air gap Ta for the designed DWP unit cell , are shown in Fig. ϕuu does not depend on the air gap Ta, whereas the reflected field phase ϕvv of the orthogonal polarization varies periodically from 0 to 2π with changing the air gap  configurationios Fig. . By vary nm Fig. . Note throl Fig. . The nanTa, thus relaxing the requirement for small, nm-sized, air gaps essential for the previously developed MEMS-OMS configurations22 and thereby simplifying the assembly process. We should however note that the access to nm-sized air gaps, although not easily gained, would allow one to operate the DWP with gap surface plasmons being generated22, a regime that promises a slightly broader operation wavelength range as discussed below. To quantify the air gap Ta at each actuation voltage Vm, we make use of the air gap-dependent MEMS-OMS operation22 by exploiting the fact that the MEMS-OMS behaves as a mirror at periodically distributed air gaps (depending on the light wavelength used) regardless of the OMS design  was directed onto the DWP oriented at θDWP = 45°  and a polarizer while analyzing the reflected light with a spectrometer  of the DWP are rather high within the bandwidth  changing from approximately  to ,  and , respectively , as shown in Fig. x >, |y >, |r >, |l > ) in the best way, is θDWP = ∼46° , corresponding to HWP/ZWP and QWP/TQWP transformations, can be visualized at both the direct image (DI) and Fourier image (FI) planes  and detecting it with a fast photodetector, we observe relatively fast switching with rise/fall times of ~0.15/0.11 and ~0.36/0.23 ms for respective ZWP/HWP and QWP/TQWP transformations  of the DWP eigenstates into the CP basis  of the hybrid QWP-DWP component, thus enabling continuous LP rotation by tuning the DWP birefringence via tuning the air gap Ta. The reflected light polarization states measured while changing the air gap are visualized by a polarization trajectory around the equator of the Poincaré sphere . To ease steering potential practical applications, we have also investigated the polarization transformations realized for different DWP orientations  and fixed incident LP state |y >  and fixed DWP orientation θDWP = 45°  and reflecting the incident LP state , broadband operation (~100 nm near the operating wavelength of 800 nm), fast responses (<0.4 ms) and full-range birefringence control that enables completely encircling the Poincaré sphere along trajectories determined by the incident light polarization and DWP orientation. It should be noted that, given the access to nm-sized air gaps, one can exploit the same design principle to realize the DWP with gap surface plasmons being generated22, a regime that promises a broader operation wavelength range (~160 nm) although probably at the expense of a lower efficiency (~50%)22. Importantly, the general approach developed can also be applied to design a DWP operating in transmission by using a partially transmitting MEMS mirror and placing an OMS in the middle of an FP cavity25. Given that a multitude of polarization modulation capabilities can be realized with the same DWP, we believe that the demonstrated electrically driven DWP configuration with full-range birefringence control opens fascinating perspectives for successful integration of high-performance compact dynamic polarization components into future miniaturized reconfigurable/adaptive optical networks and systems27.To summarize, capitalizing on our development of the MEMS-OMS platformΛ = 250 nm and periodic boundary conditions were employed for both u and v directions. The DWP unit cell is divided into two parts of air and glass, with one gold nanobrick placed against the glass region. The corners of the nanobrick are rounded with a 5 nm radius. The refractive index of air is set as 1 and that of glass as 1.46 for all wavelengths, while the gold permittivity was interpolated as a function of wavelength from experimental tabulated values28.All numerical simulations were done using COMSOL Multiphysics version 5.6. The model is composed of a rectangular volume with a square footprint with sides u and v separately. These are used to calculate the total reflection coefficient 21rmn (tmn) denotes the reflection (transmission) coefficients for light incident on material n from material m and the materials are numbered 1, 2, 3 for respectively glass substrate, air, and gold substrate, n2 represents the refractive index of the air , and k is the wavenumber in a vacuum. Note that the effect of the OMS on the interface between the air and glass substrate is included in r12, r21, t12, and t21, and that even for normal incidence rFP are polarization-dependent due to the anisotropy of the OMS layer. The reflection coefficient r23 from the air/gold interface is calculated directly using the Fresnel equation. An illustration of the DWP geometry is shown in Supplementary Fig. rFP with varying Ta.Using this model, the complex reflection and transmission coefficients for the glass/OMS/air interface are calculated for both propagation directions  and for light linearly polarized along both 20, requiring numerical simulations including also the gold substrate in COMSOL. The results obtained using the FP equation were confirmed to give the same results as COMSOL simulations with the whole glass/nanobrick/air/gold substrate model when Ta > 100 nm for a wavelength of λ = 800 nm.For air gaps much smaller than the wavelengths, there is near-field coupling between the nanobricks and the gold substrate in addition to the FP resonancesAs a final comment, to compare with the measurements, the imaginary part of the gold permittivity is increased by three times in the simulations of Figs. The OMS for developing MEMS-OMS DWP were fabricated using electron-beam lithography (EBL), thin-film deposition, and lift-off techniques. First, a 100-nm-thick poly(methyl methacrylate)  layer and a 40-nm thick conductive polymer layer  were successively spin-coated on the glass substrate . Note that the glass substrate was preprocessed to have a 10-μm-high circular pedestal using optical lithography and wet etching, and the OMS pattern was defined on the pedestal using EBL (JEOL JSM-6500F field-emission SEM with a Raith Elphy Quantum lithography system). After development, the OMS layer was formulated by depositing a 1-nm Ti adhesion layer and a 50-nm gold layer  followed by lift-off in acetone , two beam splitters  successively, and then focused onto the DWP samples by an objective . The combination of HWP and Pol1 is used for altering the input LP states as well as the intensity. The reflected light was collected by the same objective and passed through two beam splitters  and a tube lens , generating the first direct image plane where an iris is placed for filtering out the reflected light within the DWP area. The first direct image is then transformed by a relay lens  to the corresponding Fourier image and captured by a CCD camera , according to a 2f configuration. Note that a flip lens  is used for switching between the direct and Fourier images, and a Stokes analyzer composed of a QWP  and a linear polarizer  is implemented before the CCD camera for performing full Stokes polarimetry23. Two beam splitters are configured for cross-compensating the polarization-dependent phase shifts in the beam splitters for both incidence and reflection routes.The experimental setup is shown in Supplementary Fig. Pro, Ocean Optics) and conducted measurements at the Fourier image plane. By rotating the QWP and Pol2, we recorded polarization-resolved spectra of Ix(λ), Iy(λ), Ia(λ), Ib(λ), Ir(λ), Il(λ), and the stokes parameters  are calculated as s1 = (Ix(λ) – Iy(λ))/(Ix(λ) + Iy(λ)), s2 = (Ia(λ) – Ib(λ))/(Ix(λ) + Iy(λ)), s3 = (Ir(λ) – Il(λ))/(Ix(λ) + Iy(λ)). For a reasonable comparison with the simulations, the stokes parameters  are normalized to the polarized proportion of the reflected light beam: x >, |y >, |a >, |b >, |r >, |l > ) to the incident linearly |y > polarized light power.To obtain the wavelength-resolved full Stokes parameters, we replaced the CCD camera with a fiber-coupled spectrometer  can be filtered by the Stokes analyzer.To estimate the switching speeds between different orthogonal LP and CP bases , the setup described above is modified by replacing the input laser and CCD camera with a cw Ti:sapphire laser , and a photodetector , respectively. The signals from the PD are acquired with an oscilloscope . In the measurement, the MEMS-OMS-based DWP is actuated with periodically alternating voltages and different polarizations (i.e., |Supplementary InformationPeer review fileInventory of Supporting InformationSupplementary Video S1Supplementary Video S2Supplementary Video S3Supplementary Video S4Supplementary Video S5Supplementary Video S6


This can be served as a fast, simple, and high-throughput platform for functional assessment of cell adhesion molecules in a highly predictive and reproducible manner.Cancer cells interacting with the extracellular matrix (ECM) in the tumor microenvironment is pivotal for tumorigenesis, invasion, and metastasis. Cell–ECM adhesion has been intensively studied in cancer biology in the past decades to understand the molecular mechanisms underlying the adhesion events and extracellular mechanosensing, as well as develop therapeutic strategies targeting the cell adhesion molecules. Many methods have been established to measure the cell–ECM adhesion strength and correlate it with the metastatic potential of certain cancer types. However, those approaches are either low throughput, not quantitative, or with poor sensitivity and reproducibility. Herein, we developed a novel acoustic force spectroscopy based method to quantify the cell–ECM adhesion strength during adhesion maturation process using the emerging z-Movi Cancer metastasis, where malignant cells spread from a primary site to distant organs in the body, is largely responsible for the mortality and morbidity of cancer . After dIn the tumor microenvironment, integrin receptors mediate cell adhesion with ECM ligands  ,4. Such Existing techniques established to measure the cell–ECM avidity include fixed-cell imaging based in vitro adhesion seeding assays , micropi® cell–cell avidity analyzer  and human breast cancer cell line MCF-7 (ATCC HTB-22) were cultured in RPMI1640 medium  supplemented with 10% fetal bovine serum , and kept in a humidified 37 °C incubator with 5% COThe chip needs to be cleaned and dried for at least 1 h at 37 °C before coating. The surface coating was carried out using 0.002% PLL  in PBS . For each chip, 50 μL of fresh PLL solution was prepared and pulled into the microfluidic channel using a syringe  with 10 μL volume left in the reservoir to avoid bubble formation. After 15 min-incubation at room temperature, the PLL solution was completely removed using the syringe. The chip was pulled through with air several times to remove any remaining liquid in the microfluidic channel. The PLL-coated chips were kept in a dry incubator at 37 °C with a cap onto the reservoir (to avoid evaporation) for at least 1 h. The coated chips must be used within 3 days after coating. Upon cell seeding, the chips were rehydrated by pulling in 100 μL warm PBS into the microfluidic channel, leaving about 10 μL in the reservoir to avoid bubble formation. This step was repeated once with 100 μL warm complete cell culture medium.The chip needs to be cleaned and dried for at least 1 h at 37 °C. For each chip, the glass surface was rehydrated by pulling in the following solutions to the microfluidic channel using a syringe (leave about 10 μL in the reservoir to avoid bubble formation): 200 μL 1M NaOH (incubation for 5 min), 400 μL Milli-Q water for two times, 400 μL 1 M HCl for two times (incubation for 2 min at the second time), 400 μL Milli-Q water for three times, and 400 μL PBS once. For each chip, 50 μL of 100 μg/mL fresh FN  solution in PBS was pulled into the microfluidic channel with about 10 μL left in the reservoir. The inlet was washed with 400 μL PBS three times to prevent fiber or aggregate formation and re-filled with 200 μL PBS. Chips were caped firmly and kept in the 37 °C dry incubator overnight. Before cell seeding, the FN-coated chips were washed 3 times with PBS and once with the complete culture medium. The coated chips need to be used within 3 days after coating.Target cells with at least 80% confluency were used for z-Movi experiments. Adherent cells were washed once with PBS and trypsinized using TrypLE  for 3–5 min at 37 °C. Cells were collected using the complete culture medium, and the cell density was determined using the automatic cell counter. For each chip, 20 μL of MCF-7 or A2780 cells at indicated densities were seeded into the microfluidic channel using a syringe (leave about 10 μL volume in the reservoir to avoid bubble formation). It is important to keep the chips and cells at 37 °C during cell seeding to reduce cell clumping. The inlet was washed with 400 μL complete medium three times and re-filled with 400 μL PBS. Chips were caped firmly and kept in the 37 °C dry incubator for a designated period  before z-Movi avidity assay.The viability of the cell monolayer was evaluated by adding 10 μL Trypan Blue  in the reservoir containing 50 μL medium. The Trypan Blue dilution was pulled into the microfluidic channel and incubated with the monolayer cells for 30 s to stain the dead cell population, followed by 200 μL complete culture medium to rinse out Trypan Blue. The cell viability was observed by brightfield imaging.6 cells/mL (0.3 × 106 cells) was prepared. Cells were washed once with PBS and stained with the 1× CellTrace Far Red Dye  dilution in PBS at 1 × 106 cells/mL in the dark at 37 °C for 15 min. Cells were re-suspended by pipetting every 5 min during the staining process. Approximal 5 mL complete culture medium was then added to the cell solution to stop the staining. Stained cells were washed once with PBS, re-suspended in complete culture medium at 15 × 106 cells/mL, and transferred into a 96-well plate with round bottom.Adherent cells were washed once with PBS and trypsinized using TrypLE for 3−5 min at 37 °C. Cells were collected using the complete culture medium, and the cell density was determined using the automatic cell counter. For a single run on the chip, 20 μL of 15 × 10The red-fluorescent melamine resin particles  were washed with 500 μL PBS three times and once with 500 μL complete culture medium. Beads were then incubated with FN at 10 μg/mL in 200 μL of completed culture medium for 1 h on a rotating stage at room temperature. FN-coated beads were washed three times with 500 μL complete medium and re-suspended in the complete medium (10 μL for a single run).The chip was placed on the z-Movi  stage, and the in-chip cell monolayer quality was evaluated and validated by applying force at 1000 pN for 10 s. Once the monolayer passed the validation, the medium level in the inlet was brought down to about 10 μL. 20 μL of stained effector cells were added into the reservoir and pulled into the microfluidic channel to interact with the target cell monolayer for a designated period. Depending on the effector density, up to 400 effectors that being considered as individual events will be incubated in the field of view (FOV) for the avidity measurement. During the incubation, the inlet was gently washed with complete culture medium three times to remove the remaining cells and refilled with 100 μL complete medium. After interaction, the acoustic force was applied with a linear force ramp from 0 to 1000 pN over 2.5 min. The percentage of bound cells to the monolayer under different levels of applied force was calculated simultaneously. To block FN binding with cancer cells, a FN antibody  was used. To block non-specific bindings, 2% BSA  in complete culture medium was used.The cleaning solution containing 5% bleach  was pulled into the microfluidic channel, and the chip was incubated at room temperature for at least 20 min and up to 4 h. The channel was then washed with 400 μL Milli-Q water and the glass surface was scrubbed by introducing air and moving the bubbles back and forth several times. The chip surface was scrubbed with 200 μL bleach twice, followed by pulling through (1) 400 μL bleach, (2) 400 μL Milli-Q water twice, (3) 100 μL 12M HCl , and (4) 200 μL Milli-Q water twice. The surface was then scrubbed with 400 μL 1 M NaOH twice and incubated with 1 M NaOH for 1 h. After pulling through the NaOH solution, the surface was scrubbed with 200 μL 1 M NaOH twice, followed by washing with 400 μL Milli-Q water twice. Cleaned chips were stored in the dry incubator. left); (2) fluorescence images were used to track the position of effectors (right) and, thus, judge whether the effector was lifted. During the z-Movi application, the control software will move the field of view (FOV) to the force-calibrated region of the chip based on the information stored in the chip, while the software will capture both brightfield (monolayer tracking) and fluorescence (effectors tracking) signals within the FOV for the whole force application. The region of interest (ROI) for each effector is a 12 pixel-wide circle (with the cell as the center) by default. ROIs of up to 400 effectors within the FOV were identified by the software. Effectors left the ROIs while force application would be considered as ‘lifted’ and the software tracked all ROIs automatically. Manual selections were performed after software ROI selections . Two-channel images were loaded into the software: (1) brightfield images which were used to examine the monolayer confluency and screen the effector events A, left; ffectors A, right lections B. Clustelections C. Since lections D, we strt test was performed in Prism 9 for the measurement of statistical significance. p < 0.05 was considered statistically significant. All data points with error bars are presented as mean ± standard error of the mean (S.E.M).Unpaired two-tailed Student’s ® cell–cell experimental setup  as the ‘Effectors’  on the glass surface of the chip, FN and poly-L-lysine (PLL) were used. Specifically, PLL enhances the electrostatic interaction between negatively charged ions of the cell membrane and the culture surface. Such a reaction caused the cells firmly attached to the chip surface after incubation for 2 h, which was validated using the acoustic force C. In comDissociating adherent cells from the surface of plastic culturing flasks using TrypLE caused morphological changes from flattened to round shapes. After incubation on the PLL surface for 2–4 h, most cells remained round morphology with gaps between cells C. On theNotably, in the Cell–Bead setup, we only included the adhesion events of FN-coated beads interacting with cells for data analysis and excluded the events where beads landed on the cell-free surface . Therefo6 to 75 × 106 cells/mL) is required. A2780 cells were seeded at multiple densities to determine the best condition for forming a good monolayer with minimal cell–cell gaps and maximal cell population firmly attached to the chip surface. The density of 50 × 106 cells/mL produced the optimal monolayer with majority of cells spreading out and covering most of the chip surface after 1 h incubation at 37 °C , an extremely high cell seeding density , the clumping issue became exacerbated. Indeed, after loading the MCF-7 cells into the chip at a density of 60 × 106 or 50 × 106 cells/mL, significant clumping was observed within 2–5 min, leading to large empty surfaces between clumps. Once cells clumped, they hardly spread out on the surface even with FN coating. Indeed, most of MCF-7 cells (after 2 h incubation) were lifted when the acoustic force was applied to validate the monolayer (top and middle). Overnight incubation (16 h) with FN coating at 37 °C was not feasible due to the intensive cell death induced by the sealed culturing environment without CO2 and O2 exchange. Decreasing the seeding density to 30 × 106 cells/mL effectively reduced the clumping rate and level (bottom), with an increased number of MCF-7 cells spreading out and firmly attached to the chip surface. However, it also led to low seeding confluency. Although the gaps between spreading cells were small, a certain number of ‘Effectors’ will land on and interact with the surface coating (not the monolayer cells), which must be carefully identified and excluded during data analysis  exhibited an increased confluency with similar levels of cell spreading on the surface as compared to one-time seeding at 30 × 106 cells/mL (6 or 10 × 106 cells/mL further promote the confluency of the monolayer but with noticeable cell clumping incidence. Although the clumping level is less than the one that occurred when seeding at 50 × 106 or 60 × 106 cells/mL (To improve the seeding confluency while minimizing cell clumping, a multi-seeding strategy was conducted. MCF-7 cells at 20 × 1060 × 106 A,B or 70cells/mL C. As shocells/mL A. Additicells/mL A, clumpeCell–Bead setup in We then used the optimized monolayer of A2780 cells as proof of concept for cell–ECM avidity measurement (i.e., We next performed the cell–ECM avidity measurement C. To visin vivo. Moreover, by measuring the avidity of hundreds of ‘Target–Effector’ pairs in parallel with minimum cell damage with high sensitivity, this method is of great potential for preclinical drug screening to identify new candidates with potential anti-metastatic properties in a high-throughput manner.In brief, we have established a novel high-throughput measuring platform using the emerging acoustic force-dependent z-Movi technology to determine the adhesion strength of different types of cancer cells on ECM in vitro. This robust and highly maneuverable method will offer a rapid and simple solution to perform predictive, reproducible, and fast characterization of bona fide interactions between tumor cells and ECM components. More importantly, z-Movi allows us to capture early adhesion events and quantitate the adhesion strength from the initial cell attachment, flattening, to fully spreading on ECM, which cannot be achieved by traditional methods. Furthermore, given that acoustic force causes minimal damage to live cells, this system is suitable for studying fragile cells like primary patient samples and cancer stem cells, regardless of the tumor types. Although the experimental setup is designed for in vitro testing, the adhesion strength quantified by z-Movi serves as a general marker to predict the metastatic potential of the cancer cells