Polydimethylsiloxane Substrate Research Articles

Flexible Ag@Au core–shell nanowires electrode fabrication with controllable nanogold size and thickness on silver nanowires/PDMS substrate toward enhanced ethanol electrooxidation

The synthesis of gold nanowires (AuNWs) is challenging due to difficulties in obtaining AuNWs of variable diameters and lengths. In this study, an effective approach to fabricating AuNWs with controllable lengths and diameters was developed on a flexible silver nanowires (AgNWs)/polydimethylsiloxane (PDMS) substrate. Gold nanoparticles were uniformly electrodeposited onto the flexible AgNWs/PDMS to form bimetallic Ag@Au core–shell NWs/PDMS. The results showed that the diameters and the lengths of the Ag@Au NWs were easily fine-tuned. The flexible Ag@Au NWs/PDMS electrode exhibited excellent mechanical, electrical, and electrochemical properties. In ethanol oxidation reaction (EOR), the Ag@Au NWs/PDMS achieved a peak current density of 28541.55 μA cm−2 (10 times higher than that of a commercial Au electrode) and 63.39% retaining activity in a stability test by chronoamperometry (over 2 times stable than values in literature). Finally, EOR and chromium (VI) determination by the Ag@Au NWs/PDMS in flexible integrated electrodes were performed to showcase the versatile feasibilities of this new material.

Microfluidic device with three-dimensional microtip electrodes for efficient capture and concentration of bacteria-sized microparticles using dielectrophoresis

Microfluidics-based systems have gained considerable attention in the lab-on-chip field owing to their ability to separate, concentrate, and analyze microparticles. Concentrating microparticles is crucial for the high-sensitivity measurement of biomarkers in the analysis of cells or bacteria. This study presents a microfluidic chip using dielectrophoresis (DEP) to capture bacterial microparticles. The chip features a vertically arranged microtip electrode and an indium tin oxide (ITO) electrode, enhancing the electric field concentration effect and enabling optical analysis of the collected particles. The device was designed and fabricated using microfabrication techniques that incorporate a patterned array of microtip electrodes on a polydimethylsiloxane (PDMS) substrate. Experimental studies and numerical simulations were conducted to evaluate the device performance. The fabricated device was applied to the concentration of fluorescent beads with various variables such as particle size, frequency, voltage, and flow rate. The experimental results demonstrated the successful trapping and concentration of microparticles using DEP forces. The recovery rates of the 2.29 µm and 4.42 µm PS beads, when introduced at a flow rate of 1 μL/min and subjected to an applied alternating current (AC) voltage of 200 kHz and 10 Vpp at the microtip electrode, were measured to be 85.50±2.69 % and 91.83±0.63 %, respectively. Additionally, to assess the applicability of the microtip electrode-based DEP device proposed here for bacteria concentration, capture experiments were conducted using Escherichia coli, demonstrating a recovery rate performance of 77.93±7.31 %. These findings highlight the potential of the proposed microfluidic chip for the concentration and measurement of bacteria, such as E. coli.

Directed Differentiation of Adipose-Derived Stem Cells Using Imprinted Cell-Like Topographies as a Growth Factor-Free Approach.

The influence of surface topography on stem cell behavior and differentiation has garnered significant attention in regenerative medicine and tissue engineering. The cell-imprinting method has been introduced as a promising approach to mimic the geometry and topography of cells. The cell-imprinted substrates are designed to replicate the topographies and dimensions of target cells, enabling tailored interactions that promote the differentiation of stem cells towards desired specialized cell types. In fact, by replicating the size and shape of cells, biomimetic substrates provide physical cues that profoundly impact stem cell differentiation. These cues play a pivotal role in directing cell morphology, cytoskeletal organization, and gene expression, ultimately influencing lineage commitment. The biomimetic substrates' ability to emulate the native cellular microenvironment supports the creation of platforms capable of steering stem cell fate with high precision. This review discusses the role of mechanical factors that impact stem cell fate. It also provides an overview of the design and fabrication principles of cell-imprinted substrates. Furthermore, the paper delves into the use of cell-imprinted polydimethylsiloxane (PDMS) substrates to direct adipose-derived stem cells (ADSCs) differentiation into a variety of specialized cells for tissue engineering and regenerative medicine applications. Additionally, the review discusses the limitations of cell-imprinted PDMS substrates and highlights the efforts made to overcome these limitations.

Mechanical and electrical properties of α-MoO3 belts under strain for flexible electronics applications

This study investigated a straightforward and cost-effective method for synthesizing α-MoO3 belts and evaluated their potential as substrates for flexible electronic devices. Transparent α-MoO3 belts, featuring millimeter-scale side lengths and micrometer-scale thicknesses, were produced through a one-step sintering process using metallic molybdenum powder. When affixed to stretchable substrates, the α-MoO3 belts demonstrated robust mechanical stability under continuous and sustained tensile strain in the longitudinal direction. The belts exhibited a transmittance exceeding 68 % in the visible and near-infrared light regions. The current between gold dots on belts fixed to a stretchable polydimethylsiloxane substrate increased with the application of tensile strain. Furthermore, a CoFe2O4 thin film deposited at elevated temperature onto an α-MoO3 belt exhibited significant magnetic anisotropy. These findings introduce a novel and efficient approach for fabricating highly crystalline thin films on stretchable and bendable substrates using α-MoO3 belts.

Parallel Concentric Wrinkled Polydimethylsiloxane Patterns and Their Potential Biomedical Applications

AbstractThe objective of this study is to examine microbial behavior by fabricating and applying parallel concentric wrinkled patterns to polydimethylsiloxane (PDMS) substrates. The patterns are generated and subsequently relaxed in a rigid silica layer, resulting in the formation of discernible wrinkles that can be analyzed using electron microscopy and light diffraction. The alignment of E. coli and silica microparticles is facilitated by these structures along the creases. Within these creases, E. coli exhibits enhanced attachment and rotational mobility in regions characterized by hydrophobic cracks. Furthermore, the bacteria demonstrate an increase in velocity when propelled by the PDMS creases, suggesting that these structures are capable of guiding microbial motion. In addition, distinct alignment and growth patterns are observed for E. coli proliferation within the PDMS microchannels under confined conditions. The analysis of bacterial morphology and gene expression in response to chemical stimuli, such as isopropyl‐β‐D‐thiogalactopyranoside (IPTG) gradients, demonstrates that the chemical environment has a substantial impact; filamentous cells aligned along the creases. These results illustrate the efficacy of parallel concentric wrinkled PDMS patterns in establishing regulated conditions for investigating microbial behavior and represent significant contributions to the fields of microbiology and biomedicine.

Substrate stiffness modulates extracellular vesicles’ release in a triple-negative breast cancer model

Aim: The microenvironment effect on the tumoral-derived Extracellular Vesicle release, which is of significant interest for biomedical applications, still represents a rather unexplored field. The aim of the present work is to investigate the interrelation between extracellular matrix (ECM) stiffness and the release of small EVs from cancer cells. Here, we focus on the interrelation between the ECM and small extracellular vesicles (sEVs), specifically investigating the unexplored aspect of the influence of ECM stiffness on the release of sEVs. Methods: We used a well-studied metastatic Triple-Negative Breast Cancer (TNBC) cell line, MDA-MB-231, as a model to study the release of sEVs by cells cultured on substrates of different stiffness. We have grown MDA-MB-231 cells on two collagen-coated polydimethylsiloxane (PDMS) substrates at different stiffness (0.2 and 3.6 MPa), comparing them with a hard glass substrate as control, and then we isolated the respective sEVs by differential ultracentrifugation. After checking the cell growth conditions [vitality, morphology by immunofluorescence microscopy, stiffness by atomic force microscopy (AFM)], we took advantage of a multi-parametric approach based on complementary techniques (AFM, Nanoparticle Tracking Analysis, and asymmetric flow field flow fractionation with a multi-angle light scattering detector) to characterize the TNBC-derived sEV obtained in the different substrate conditions. Results: We observe that soft substrates induce TNBC cell softening and rounding. This effect promotes the release of a high number of larger sEVs. Conclusion: Here, we show the role of ECM physical properties in the regulation of sEV release in a TNBC model. While the molecular mechanisms regulating this effect need further investigation, our report represents a step toward an improved understanding of ECM-cell-sEVs crosstalk.

Simulation of Polymer Fractal Formation Using a Triangular Network Growth Model.

Fractal formation in spin-coated thin-film polymers is of experimental and theoretical interest. Modeling the determinants and dynamics of this process will deepen our understanding of polymer aggregation and the predictability of thin-film structures. This is especially true if the model used has readily interpretable parameters and has been demonstrated to yield a close match to experimental processes under a variety of conditions. In this work, we adapted and applied a relatively new model of fractal growth comprised of a spreading and contracting triangular network, to model spin-coated, thin-film polymers made of poly(vinyl alcohol) on polydimethylsiloxane substrates. We drew clear connections between model parameters and the process of polymer aggregation and we demonstrated the ability of the model to simulate fractal formation under a wide variety of conditions including varying the degree of hydrolysis of the polymer, changing the spin-coating process, and solvent annealing and reforming of polymer fractals under different drying conditions. We also showed how the model is able to replicate idiosyncratic experimental settings yielding novel fractal patterns.

Flexible AgNW/PDMS nanocomposite for strain and pressure sensing

This study presents the fabrication and characterization of an ultra-thin (<1 mm) piezoresistive sensor based on a silver nanowire (AgNW) and polydimethylsiloxane (PDMS) nanocomposite, capable of simultaneous strain and pressure sensing. The sensor exhibits high sensitivity, detecting strains as low as 0.5 % with a range of up to 40 %, demonstrates frequency responsiveness from 0.5 to 3 Hz, and maintains functionality over 1000 cycles. The sensor’s performance was evaluated through cyclic tensile and compressive tests. We hypothesize that the compression sensing mechanism is a consequence of the Poisson effect in the PDMS substrate, where transverse compression induces axial strains parallel to the AgNW network, causing disconnections within the nanowire matrix. The sensor’s versatility was demonstrated through various biofeedback applications, including finger bending, applied pressure, calf raises, and elbow flexion. With its thin profile and dual-mode sensing capability, this AgNW/PDMS nanocomposite sensor shows promise for biomechanics, sports science, and healthcare monitoring applications.

EDA Fibronectin Microarchitecture and YAP Translocation During Wound Closure.

Fibronectin (Fn) is an extracellular matrix glycoprotein with mechanosensitive structure-function. EDA Fn, a Fn isoform, is not present in adult tissue but is required for tissue repair. Curiously, EDA Fn is linked to both regenerative and fibrotic tissue repair. Given that Fn mechanoregulates cell behavior, Fn EDA organization during wound closure might play a role in mediating these differing responses. One mechanism by which cells sense and respond to their microenvironment is by activating a transcriptional co-activator, Yes-associated protein (YAP). Interestingly, YAP activity is not only required for wound closure, but similarly linked to both regenerative and fibrotic repair. Therefore, this study aims to evaluate how, during normal and fibrotic wound closure, EDA Fn organization might modulate YAP translocation by culturing human dermal fibroblasts on polydimethylsiloxane (PDMS) substrates mimicking normal (soft: 18 kPa) and fibrotic (stiff: 146 kPa) wounded skin. On stiffer substrates mimicking fibrotic wounds, fibroblasts assembled an aligned EDA Fn matrix comprising thinner fibers, suggesting increased microenvironmental tension. To evaluate if cell binding to the EDA domain of Fn was essential to overall matrix organization, fibroblasts were treated with Irigenin, which inhibits binding to the EDA domain within Fn. Blocking adhesion to EDA led to randomly organized EDA Fn matrices with thicker fibers, suggesting reduced microenvironmental tension even during fibrotic wound closure. To evaluate if YAP signaling plays a role in EDA Fn organization, fibroblasts were treated with CA3, which suppresses YAP activity in a dose-dependent manner. Treatment with CA3 also led to randomly organized EDA Fn matrices with thicker fibers, suggesting a potential connected mechanism of reducing tension during fibrotic wound closure. Next, YAP activity was assessed to evaluate the impact of EDA Fn organization. Interestingly, fibroblasts migrating on softer substrates mimicking normal wounds increased YAP activity but on stiffer substrates, decreased YAP activity. When fibroblasts on stiffer substrates were treated with Irigenin or CA3, fibroblasts increased YAP activity. These results suggest there may be disrupted signaling between EDA Fn organization and YAP translocation during fibrotic wound closure that could be restored when reestablishing normal EDA Fn matrix organization to instead drive regenerative wound repair.

Dynamic electromechanical characterizations of poly(vinylidene fluoride) based nanocomposite films on ultra‐low modulus polymer substrate

AbstractThis article explores the electromechanical performance of poly(vinylidene fluoride) (PVDF) films with silver nanoplatelets on smooth polydimethylsiloxane (PDMS) substrates. PVDF, a semi‐crystalline polymer, shows piezoelectric properties when processed at low temperatures, making it ideal for energy harvesting and sensors. This research addresses a gap by examining high strain rate and complex electromechanical characteristions of PVDF composites, which are underexplored. Films, fabricated using a non‐vacuum rod coating method, underwent dynamic electromechanical tests (strain rate ~ 2 s−1), including stretching, twisting, combined stretching and twisting, and forced vibrations. Results show the films function up to 17% applied strain with a gage factor of 10.57. In twisting tests, the laminates perform up to 387° in slow twisting (gage factor = 28.34) and 341° in fast twisting (gage factor = 7.65). Combined stretching and twisting tests show performance decreases, with functionality up to 6.24% strain at a twist angle of 330.1°. Vibration tests reveal that increased amplitude reduces performance, with the laminates enduring frequencies between 4.35 and 12.14 Hz. The films also exhibit a linear piezoelectric response, with a maximum open circuit voltage of 37.2 V under an impact load of 1112 N, underscoring the potential of PVDF/Ag nanocomposites for advanced MEMS applications.

The modulation of lung cancer cell motility by Calponin 3 is achieved through its ability to sense and respond to changes in substrate stiffness.

The influence of extracellular matrix (ECM) stiffness on cell behavior is a well-established phenomenon. Tumor development is associated with the stiffening of the ECM. However, the understanding of the role of biomechanical behavior and mechanotransduction pathways in the oncogenesis of tumor cells remains limited. In this study, we constructed in vitro models using Polydimethylsiloxane substrates to create soft and stiff substrates. We then evaluated the migration of lung cancer cells A549 using video-microscopy and transwell assays. The mechanical properties were assessed through the utilization of atomic force microscopy, Optical Magnetic Twisting Cytometry, and traction force analysis. Additionally, the expression of Calponin 3 (CNN3) was evaluated using reverse transcription‑quantitative PCR and immunofluorescence techniques. Our observations indicate that the presence of a stiff substrate enhances A549 motility, as evidenced by increased stiffness and traction force in A549 cells on the stiff substrate. Furthermore, we observed a decrease in CNN3 expression in A549 cells on the stiff substrate. Notably, when CNN3 was overexpressed, it effectively inhibited the migration and invasion of A549 cells on the stiff substrate. The results of our study provide novel perspectives on the mechanisms underlying cancer cell migration in response to substrate mechanical properties.

A new method for estimating nanoparticle deposition coverage from a set of weak-contrast SEM images

Imaging nanomaterials in hybrid systems is critical to understanding the structure and functionality of these systems. However, current technologies such as scanning electron microscopy (SEM) may obtain high resolution/contrast images at the cost of damaging or contaminating the sample. For example, to prevent the charging of organic substrate/matrix, a very thin layer of metal is coated on the surface, which will permanently contaminate the sample and eliminate the possibility of reusing it for following processes. Conversely, examining the sample without any modifications, in pursuit of high-fidelity digital images of its unperturbed state, can come at the cost of low-quality images that are challenging to process. Here, a solution is proposed for the case where no brightness threshold is available to reliably judge whether a region is covered with nanomaterials. The method examines local brightness variability to detect nanomaterial deposits. Very good agreement with manually obtained values of the coverage is observed, and a strong case is made for the method's automatability. Although the developed methodology is showcased in the context of SEM images of Polydimethylsiloxane (PDMS) substrates on which silicone dioxide (SiO2) nanoparticles are assembled, the underlying concepts may be extended to situations where straightforward brightness thresholding is not viable.

Heterogeneous micro-architectonic integration of SU-8 and highly entangled polyacrylamide hydrogel to realize cut-resistant soft superhydrophobic surfaces

This paper presents a novel idea to create cut-resistant superhydrophobic (SHPo) surfaces by integrating an array of SU-8 micropillars on a highly entangled polyacrylamide (PAAm) hydrogel substrate. We begin by demonstrating that this highly entangled PAAm hydrogel exhibits superior resistance to cutting while being as transparent, flexible, and stretchable as other polymeric substrates like polydimethylsiloxane (PDMS). Currently, there are no well-known methods or chemicals to directly integrate SU-8 and PAAm with a covalent bond. To overcome this challenge, we introduce a thin layer of chemically modified PDMS between the SU-8 and PAAm so that covalent bonds can be formed between both the SU-8/PDMS interface and the PDMS/PAAm interface. After validating the reliability of the bonding in our experiments, we develop a heterogeneous integration process to fabricate the desired SHPo surface. To demonstrate the critical role of PAAm hydrogel in achieving the cut-resistant SHPo surface, we contrast this new SHPo surface with a reference version that uses a PDMS substrate instead. We conduct microscopic inspections using scanning electron microscopy (SEM) and a contact angle goniometer before and after cutting the two surfaces. These evaluations show significant differences in their structural integrity and behavior in water interaction.

Sensing with Thermally Reduced Graphene Oxide under Repeated Large Multi-Directional Strain.

This paper presents a recent investigation into the electromechanical behavior of thermally reduced graphene oxide (rGO) as a strain sensor undergoing repeated large mechanical strains up to 20.72%, with electrical signal output measurement in multiple directions relative to the applied strain. Strain is one the most basic and most common stimuli sensed. rGO can be synthesized from abundant materials, can survive exposure to large strains (up to 20.72%), can be synthesized directly on structures with relative ease, and provides high sensitivity, with gauge factors up to 200 regularly reported. In this investigation, a suspension of graphene oxide flakes was deposited onto Polydimethylsiloxane (PDMS) substrates and thermally reduced to create macroscopic rGO-strain sensors. Electrical resistance parallel to the direction of applied tension (x^) demonstrated linear behavior (similar to the piezoresistive behavior of solid materials under strain) up to strains around 7.5%, beyond which nonlinear resistive behavior (similar to percolative electrical behavior) was observed. Cyclic tensile testing results suggested that some residual micro-cracks remained in place after relaxation from the first cycle of tensile loading. A linear fit across the range of strains investigated produced a gauge factor of 91.50(Ω/Ω)/(m/m), though it was observed that the behavior at high strains was clearly nonlinear. Hysteresis testing showed high consistency in the electromechanical response of the sensor between loading and unloading within cycles as well as increased consistency in the pattern of the response between different cycles starting from cycle 2.

Oriented Alignment of CsPbBr3 Single-Crystal Arrays for Flexible X-ray Imaging.

The utilization of perovskite materials in flexible optoelectronics is experiencing distinct diversification including X-ray detection applications. Here, we report the oriented alignment of cesium lead bromide (CsPbBr3) single-crystal arrays on flexible polydimethylsiloxane (PDMS) substrates. By precisely confining the crystallization process within spatially delimited precursor droplets, we achieve a well-oriented crystal alignment through the spontaneous rotation of the CsPbBr3 microcuboids. This approach allows for precise control over the microcuboid morphologies by varying the growth temperature. We design flexible X-ray detector arrays by seamlessly integrating CsPbBr3 microcuboids with electrode arrays. The flexible X-ray detector can output a high sensitivity of 1.97 × 105 μC·Gyair-1·cm-2 and a low detection limit of 89 nGyair·s-1 after the surface passivation process. The excellent mechanical properties, outstanding X-ray detection capabilities, and high pixel uniformity are also demonstrated in conformal X-ray imaging of curved surfaces.

Phosphatidylserine-functional polydimethylsiloxane substrates regulate macrophage M2 polarization via modulus-dependent NF-κB/PPARγ pathway

Macrophages, highly plastic innate immune cells, critically influence the success of implantable devices by responding to biochemical and physical cues. However, the mechanisms underlying their synergistic regulation of macrophage polarization on implant surfaces remain poorly understood. Therefore, we constructed anti-inflammatory phosphatidylserine (PS) modified polydimethylsiloxane (PDMS) substrates with low, medium, and high modulus (1–100 kPa) to investigate the combined effects and underlying mechanisms of substrate modulus and biochemical signal on macrophage polarization. The introduction of PS on the PDMS surface not only significantly enhanced the polarization of M0 to M2 but also potently suppressed lipopolysaccharide (LPS)-induced M1 activation, with this effect further potentiated by a reduction in substrate modulus. In vivo subcutaneous implantation experiments also corroborated the synergistic effect of PS functionalization and low modulus PDMS in inhibiting M1 activation and promoting M2 polarization. Notably, reduced modulus led to decreased integrin αV/β3 clustering and cytoskeletal protein aggregation, ultimately diminishing YAP activation and nuclear translocation. Concomitantly, this disruption of the Piezo1-cytoskeletal protein positive feedback loop resulted in reduced p65/IκB phosphorylation and inflammation, while concurrently promoting PPARγ expression. Overall, our findings underscore the pivotal role of substrate modulus in modulating PS-mediated biomaterial-cell interactions, synergistically potentiating PS-induced M2 macrophage polarization, thus paving the way for the design of advanced immunomodulatory biomaterials.

Flexible Transparent Films of Oriented Silver Nanowires for a Stretchable Strain Sensor.

The potential applications of stretchable strain sensors in wearable electronics have garnered significant attention. However, developing susceptible stretchable strain sensors for practical applications still poses a considerable challenge. The present study introduces a stretchable strain sensor that utilizes silver nanowires (AgNWs) embedded into a polydimethylsiloxane (PDMS) substrate. The AgNWs have high flexibility and electrical conductivity. A stretchable AgNW/Pat-PDMS conductive film was prepared by arranging nanowires on the surface of PDMS using a simple rod coating method. Depending on the orientation angle, the overlap area between nanowires varies, resulting in different levels of separation under a given strain. Due to the separation of the nanowire and the change in current path geometry, the variation in strain resistance of the sensor can be primarily attributed to these factors. Therefore, precision in strain regulation can be adjusted by altering the angle θ (0°, 60°, or 90°) of the nanowire. At the same time, the stability of the AgNW/Pattern-PDMS (AgNW/Pat-PDMS) conductive film application was verified by preparing a sandwich structure PDMS/AgNW/Pat-PDMS stretchable strain sensor. The sensor exhibited high sensitivity within the operating sensing range (gauge factor (GF) of 15 within ~120% strain), superior durability (20,000 bending cycles and 5000 stretching cycles), and excellent response toward bending.

Facile assembly of flexible, stretchable and attachable symmetric microsupercapacitors with wide working voltage windows and favorable durability

With the increasing development of intelligent robots and wearable electronics, the demand for high-performance flexible energy storage devices is drastically increasing. In this study, flexible symmetric microsupercapacitors (MSCs) that could operate in a wide working voltage window were developed by combining laser-direct-writing graphene (LG) electrodes with a phosphoric acid-nonionic surfactant liquid crystal (PA-NI LC) gel electrolyte. To increase the flexibility and enhance the conformal ability of the MSC devices to anisotropic surfaces, after the interdigitated LG formed on the polyimide (PI) film surface, the devices were further transferred onto a flexible, stretchable and transparent polydimethylsiloxane (PDMS) substrate; this substrate displayed favorable flexibility and mechanical characteristics in the bending test. Furthermore, the electrochemical performances of the symmetric MSCs with various electrode widths (300, 400, 500 and 600 μm) were evaluated. The findings revealed that symmetric MSC devices could operate in a large voltage range (0–1.5 V); additionally, the device with a 300 μm electrode width (MSC-300) exhibited the largest areal capacitance of 2.3 mF cm−2 at 0.07 mA cm−2 and an areal (volumetric) energy density of 0.72 μWh cm−2 (0.36 mWh cm−3) at 55.07 μW cm−2 (27.54 mW cm−3), along with favorable mechanical and cycling stability. After charging for ~20 s, two MSC-300 devices connected in series could supply energy to a calculator to operate for ~130 s, showing its practical application potential as an energy storage device. Moreover, the device displayed favorable reversibility, stability and durability. After 12 months of aging in air at room temperature, its electrochemical performance was not altered, and after charging-discharging measurements for 5000 cycles at 0.07 mA cm−2, ~93.6% of the areal capacitance was still retained; these results demonstrated its practical long-term application potential as an energy storage device.

A flexible nanostructured multimodal sensor based on surface plasmon resonance

Biosensors are of great significance for human health and safety monitoring, especially the sensor based on Surface Plasmon Resonance (SPR), widely used in biomolecular detection. Improving its sensitivity has always been the focus of research. In this paper, SPR in grating structures was primarily investigated and then a SPR-based nanoscale metal grating sensor was proposed. With Finite Difference Time Domain (FDTD) simulation, optimization of the sensor's duty ratio, thickness of the Gold (Au) layer, and periodic parameters was conducted. Then sensitivity and quality factor of the sensor are analyzed to obtain the optimal sensor parameters. With a grating period of 0.64 μm, Au layer thickness of 30 nm, and sensor's fill factor of 0.625, the sensor achieves a sensitivity of 0.417 μm/refractive index unit (RIU), demonstrating optimal performance. Additionally, Abaqus tensile simulations were performed on the grating imprinting section, validating the uniformity and consistency of strain in the Polydimethylsiloxane (PDMS) substrate-Au film grating structure during stretching. Finally, a combination mold based on acrylic material is designed, effectively addressing the challenging demolding characteristics of cured PDMS material, offering an efficient manufacturing approach for PDMS substrate fabrication. The SPR-based nanoscale grating multimodal sensor designed in this paper exhibits high sensitivity and potential cost-effectiveness in protein molecule detection and flexible stress-strain sensing applications, revealing promising broad prospects for practical utilization.

Flexible and multi-functional three-dimensional scaffold based on enokitake-like Au nanowires for real-time monitoring of endothelial mechanotransduction

Endothelial cells are sensitive to mechanical force and can convert it into biochemical signals to trigger mechano-chemo-transduction. Although conventional techniques have been used to investigate the subsequent modifications of cellular expression after mechanical stimulation, the in situ and real-time acquiring the transient biochemical information during mechanotransduction process remains an enormous challenge. In this work, we develop a flexible and multi-functional three-dimensional conductive scaffold that integrates cell growth, mechanical stimulation, and electrochemical sensing by in situ growth of enokitake-like Au nanowires on a three-dimensional porous polydimethylsiloxane substrate. The conductive scaffold possesses stable and desirable electrochemical sensing performance toward nitric oxide under mechanical deformation. The prepared e-AuNWs/CC/PDMS scaffold exhibits a good electrocatalytic ability to NO with a linear range from 2.5 nM to 13.95 μM and a detection limit of 8 nM. Owing to the excellent cellular compatibility, endothelial cells can be cultured directly on the scaffold and the real-time inducing and recording of nitric oxide secretion under physiological and pathological conditions were achieved. This work renders a reliable sensing platform for real-time monitoring cytomechanical signaling during endothelial mechanotransduction and is expected to promote other related biological investigations based on three-dimensional cell culture.