Polydimethylsiloxane Film Research Articles

Repackaging and Performance Analysis of Implantable Pressure Sensor

In recent years, repackaging technology has been widely used in miniaturized implantable pressure sensors. However, the current packaging structure still has significant problems regarding biocompatibility, environmental adaptability, and measurement accuracy, which greatly limits its application in vivo measurement systems. In this paper, we report a method for implantable pressure sensor repackaging based on silicone oil, polydimethylsiloxane (PDMS) film, and polymer (parylene) coating. A systematic investigation using finite element analysis is conducted to assess the impact of packaging components on sensor performance, providing a solid theoretical foundation for packaging optimization. Experimental results demonstrate that when the parylene coating thickness is below 30 µm, the sensors exhibit superior linearity, repeatability, and reliability, along with exceptional stability and dynamic response across clinically relevant pressure ranges. This research provides valuable insights into the packaging design of implantable pressure sensors, facilitating the development of more stable, reliable, and cost-effective sensors for in vivo measurement systems.

A Tribo/Piezoelectric Nanogenerator Based on Bio-MOFs for Energy Harvesting and Antibacterial Wearable Device.

New types of metal-organic framework (MOF) materials have great potential in solving the current global dilemma on energy, environment, and medical care. Herein, based on two kinds of biomolecule-MOFs (Bio-MOFs) with favorable biocompatibility and degradation-reconstruction characteristics, we have established a self-powered muti-functional device to achieve an efficient and broad-spectrum environmental energy collection and biomedical applications. Combining Zn(II) and carnosine-based Zn-Car_MOF possessing a high piezoelectric response (d33 = 11.17 pm V-1) with patterned polydimethylsiloxane (PDMS) film, a tribo-piezoelectric hybrid nanogenerator (TPHG) is constructed with a synergy output of triboelectric and piezoelectric effects. The Zn-Car_TPHG demonstrates a high output performance (131V at 100kPa) and a wide range of pressure response (1Pa-100kPa), possessing applications in environmental energy collection and biomedical sensors. To expand the application of the wearable device, a conductive hexagonal prism MOF (Cu3(2,3,6,7,10,11-hexahydroxytriphenylene)2 (Cu-HHTP)) is synthesized and employed to load thymol (Thy). Cooperating with Zn-Car_TPHG, the resulting Cu-HHTP/Thy can achieve an efficient self-powered ROS (singlet oxygen (1O2) and hydroxyl radical (·OH)) generation and drug synergistic broad-spectrum sterilization effect (efficiency ≥ 98%). In a word, the flexible wearable device based on the muti-functional Bio-MOFs is sustainable and environmentally friendly, possessing wide application potential in fields of environmental energy collection, biosensors, and self-powered antibacterial.

Micropatterned CuS@PDMS films with anti-adhesive property for photothermal sterilization

This study presents the development of micropatterned polydimethylsiloxane (PDMS) films with hollow CuS NPs (p-CuS@PDMS) designed for both anti-adhesive and photothermal sterilization applications. Hollow CuS nanoparticles (NPs) synthesized via the Kirkendall effect were incorporated into PDMS films to enhance the photothermal conversion. Micropatterning, achieved through a yogurt lid templating method, increased surface roughness and hydrophobicity and significantly reduced bacterial adhesion. The improved anti-adhesive properties were demonstrated by water contact angle measurements, which showed an increase of 24° from 103° to 127° for the micropatterned p-CuS@PDMS films. Under near-infrared (NIR) irradiation, the p-CuS@PDMS films achieved a temperature increase of 91 °C with a photothermal conversion efficiency of 73 %, which is much higher than the 61 °C achieved by plain PDMS. The presence of CuS NPs in the PDMS matrix improved the bacterial inactivation rates, with p-CuS@PDMS achieving a 99 % bacterial kill rate after 90 s of irradiation. Although the anti-adhesive properties were influenced more by micropatterning, the combination of CuS and micropatterning provided a synergistic effect. These results demonstrate the potential of p-CuS@PDMS films for applications in healthcare and packaging, where effective sterilization and bacterial resistance are critical.

A smart finger patch with coupled magnetoelastic and resistive bending sensors

In the era of Metaverse and virtual reality (VR)/augmented reality (AR), capturing finger motion and force interactions is crucial for immersive human-machine interfaces. This study introduces a flexible electronic skin for the index finger, addressing coupled perception of both state and process in dynamic tactile sensing. The device integrates resistive and giant magnetoelastic sensors, enabling detection of surface pressure and finger joint bending. This e-skin identifies three phases of finger action: bending state, dynamic normal force and tangential force (sweeping). The system comprises resistive carbon nanotubes (CNT)/polydimethylsiloxane (PDMS) films for bending sensing and magnetoelastic sensors (NdFeB particles, EcoFlex, and flexible coils) for pressure detection. The inward bending resistive sensor, based on self-assembled microstructures, exhibits directional specificity with a response time under 120 ms and bending sensitivity from 0° to 120°. The magnetoelastic sensors demonstrate specific responses to frequency and deformation magnitude, as well as sensitivity to surface roughness during sliding and material hardness. The system’s capability is demonstrated through tactile-based bread type and condition recognition, achieving 92% accuracy. This intelligent patch shows broad potential in enhancing interactions across various fields, from VR/AR interfaces and medical diagnostics to smart manufacturing and industrial automation.

Achieving a Porous PDMS Film for Passive Cooling through the Utilization of Ultrafine NaCl Sacrificial Templates.

Passive radiative cooling technology serves as an energy-free alternative to traditional cooling systems. Porous polymer structures are frequently employed for radiative cooling by leveraging the refractive index mismatch between the polymer and the pores, enabling the scattering of incoming sunlight. Recently, water-soluble and readily available Sodium chloride (NaCl) particles have been utilized as sacrificial templates for sustainable pore creation. Nevertheless, optimizing NaCl particle size, and thus the polymer pore size to enhance scattering capabilities remains a challenge. Here, we report a simple, scalable, and sustainable approach to creating an optimized porous polydimethylsiloxane (PDMS) film. This approach utilizes ultrafine NaCl powders as sacrificial templates, which were synthesized via ultrasonic precipitation to ensure their small size. The ultrafine NaCl particles have a size distribution centered around 6-8 μm, and the as-fabricated porous PDMS film achieves a high thermal emissivity of 0.95 within the atmospheric window (8-13 μm) and exhibits a reflectivity of 0.95 within the visible range (0.4-0.78 μm). Due to the desired dual-spectrum properties, the porous PDMS film exhibits a superior subambient cooling capacity over that fabricated with typically larger NaCl particles under strong sunlight. This study offers a scalable and practical radiative cooling solution for sustainable thermal management.

High-Efficiency Fluorescent-Coupled Optical Fiber Passive Tactile Sensor with Integrated Microlens for Surface Texture and Roughness Detection.

Integrating ZnS:Cu@Al2O3/polydimethylsiloxane (PDMS) flexible matrices with optical fibers is crucial for the development of practical passive sensors. However, the fluorescence coupling efficiency is constrained by the small numerical aperture of the fiber, leading to a reduction in sensor sensitivity. To mitigate this limitation, a microsphere lens was fabricated at the end of the multimode fiber, which resulted in a 21.585% enhancement in the fluorescence coupling efficiency. A passive, flexible mechanoluminescent (ML) tactile sensor (MLTS) was developed by embedding a fiber microsphere probe within a ZnS:Cu@Al2O3/PDMS film featuring a pyramid surface structure. The MLTS demonstrated exceptional pressure sensing capabilities, exhibiting rapid response times of 250 ms for loading and 200 ms for unloading, along with strong durability, surviving over 2000 cycles. It effectively distinguished Braille patterns and sandpapers of varying roughness by detecting the ML signals generated by the sensor's surface microstructures. Notably, this sensor operates without the need for external light stimulation, making it a promising candidate for application in photonic skin and robotic tactile perception.

Thermal Conduction Suppresses Cracks in PDMS Wrinkling by Plasma Oxidation.

We report a facile approach to suppress intrinsic crack formation during wrinkling of plasma-oxidized polydimethylsiloxane (PDMS) films, removing a major hindrance in the practical use of these ubiquitous, functional surface patterns. A combination of high heat transfer coefficient (HTC) of the film substrate and low PDMS thickness is shown to consistently yield crack-free wrinkling of glassy skin and PDMS bilayers. Employing optical and atomic force microscopy, light scattering, thermal measurements, and heat transport and stress calculations, we demonstrate that our findings hold for a range of glass, plastic, metal, and layered support materials and plasma processing conditions. Subsuming the PDMS contribution to thermal conduction, an overall HTC threshold of ∼800 W/(m2 K), for typical plasma exposures, for crack-free wrinkling is obtained. While suppressing cracks, this simple approach retains the functionality of the glassy skin of plasma-oxidized PDMS.

Sign-Switchable Poisson's Ratio Design for Bimodal Strain-to-Electrical Signal Transducing Device.

Stretchable electronic devices that conduct strain-related electronic performances have drawn extensive attention, functioning as mechanical sensors, actuators, and stretchable conductors. Although strain-insensitive or strain-responsive nature is well-achieved separately, it remains challenging to combine these two characteristics in one single device, which will offer versatile adaptability in various working situations. Herein, a hybrid material with sign-switchable Poisson's ratio (SSPR) is developed by combining a phase-change gel based reentrantreentrant honeycomb pattern and a polydimethylsiloxane film. The phase-change gel featuring thermally-regulated Young's modulus enables the hybrid material to switch between negative and positive Poisson's ratios. After integrating with a pre-stretched silver nanowires film, the obtained stretchable device performs bimodal strain-to-electrical signal transducing (Bi-SET) functions, in which the SSPR-dominated strain-resistance response switches between strain-dependent and strain-insensitive behaviors. As a proof of concept, a mode-switchable grasping system is constructed using a Bi-SET device-based controller, enabling the adaptation of grasping behaviors to various target objects.

Effect of adding ionic liquid into polydimethylsiloxane on the output performance of triboelectric nanogenerator

Abstract Adding 1-butyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (BMIM-TFSI), an ionic liquid, to polydimethylsiloxane (PDMS) films significantly enhances the output of triboelectric nanogenerators (TENGs). In a TENG using contact and separation between the composite film and an aluminum (Al) plate, incorporating 0.1 vol% of BMIM-TFSI more than doubled the output voltage achieved compared to a pure PDMS film. To understand the cause of this improvement, composition analysis around the surface of the composite polymer film was conducted before and after tapping. We found that BMIM-TFSI molecules segregated around the surface after tapping. It is considered that the polarization of the BMIM-TFSI molecules enhances the output performance of TENGs by superimposing on the surface charges generated at the PDMS/Al interface.

Immobilization of Erythrosine Dye in Polysiloxane to Fabricate a Cost-effective Renewable Antibiotic Film through Visible Light-induced Singlet Oxygen Generation

The advanced oxidation process (AOP) is the most effective strategy to remove volatile organic compounds that are considered to be one of the main pollutants adversely affecting the environment and human health. While metal-based semiconductors are widely considered as promising photocatalysts to remove pollutants through AOP systems, their low light absorption efficiency and poor processibility remain major issues to be utilized for a sustainable AOP system with low energy consumption. However, the organic dye, erythrosine, which can generate singlet oxygens by absorbing visible light, is considered an excellent substitute for metal-based photocatalysts for cheap renewable AOP systems. Accordingly, we here demonstrate a new hybrid membrane, wherein erythrosine molecules are embedded into films of polydimethylsiloxane. The polymeric networks therefore play an important role in enhancing the thermal stability and light absorption efficiency of dye molecules upon hybridization. In addition, the foamed structures of films to enhance their porosity and oxygen permeability are introduced via the fast evaporation of ethanol. As a result, the photocatalytic performance of dyes is significantly reinforced as the porosity of the membrane increases, which is proven by analyzing the degradation efficiency of 1,3–diphenylisobenzofuran with the presence of foamed and hybridized films. The photocatalytic ability of the formed hybrid films was well regenerated in three repeated recycles. Moreover, an optical parametric oscillator (OPO) laser system was used to successfully demonstrate that the singlet oxygen generated from the optimized hybrid film was well diffused into the surface of polymer matrix. Accordingly, the film could effectively sterilize S. aureus and E. coli in an aqueous solution. Therefore, this study suggests that the hybridization of polymer and dye without chemical modification can be an effective strategy to fabricate cheap and reusable porous membranes for a practical environment purification system.

Optimization of hierarchical textured PDMS film with wide-angle broadband anti-reflection for light trapping in solar cells

We developed a hierarchical random pyramid (HRP)-polydimethylsiloxane (PDMS) film as an antireflective layer for metal halide perovskite solar cells (PSCs). To create the HRP structure on the PDMS surface, we first patterned the Si surface using alkaline etching and Ag-assisted chemical etching (Ag-ACE) and then transferred the pattern onto the PDMS surface. The resulting PDMS exhibited hierarchical structures of inverted micro-pyramids with nano-scale surface features. The optical performance of the textured PDMS film was observed across the entire wavelength range of visible light (λ = 300–800 nm), attributed to the enhanced light-trapping effect resulting from the increased fractal dimensions (Df) of the hierarchical nanostructures. Under optimal conditions, an average reflectance of 3.13 % was observed, along with a 14 % improvement in transmittance compared to that of the reference. Finite difference time-domain simulations were used to investigate the origins of these optical enhancements, conclusively linking them to the HRP structures. The optimized structures also showed superhydrophobicity with a contact angle (θCA) of approximately 155.2°. When applied to PSCs (MAPbI3), the optimized textured PDMS film led to a 12 % increase in short-circuit current density (Jsc) from approximately 23.1 to 25.98 mA/cm2. Furthermore, the power conversion efficiency of the MAPbI3 p-i-n structured devices was enhanced by 18.21 %, representing a 13 % improvement. Our results confirm that the HRP-PDMS film enhances superhydrophobicity and light trapping, while mitigating the transmittance loss due to changes in the incident angle. This study suggests potential strategies for overcoming the limitations of light absorption in solar cell applications.

A flexible high-precision photoacoustic retinal prosthesis.

Retinal degenerative diseases of photoreceptors are a leading cause of blindness with no effective treatment. Retinal prostheses aim to restore sight by stimulating remaining retinal cells. Here, we present a photoacoustic retinal stimulation technology. We designed a polydimethylsiloxane and carbon-based flexible film that converts near-infrared laser pulses into a localized acoustic field with 56-μm lateral resolution, aiming at high-precision acoustic stimulation of mechanosensitive retinal cells. This photoacoustic stimulation resulted in robust and localized modulation of retinal ganglion cell activity in both wild-type and degenerated ex vivo retinae. When a millimeter-sized photoacoustic film was implanted in the rat subretinal space, pulsed laser stimulation generated neural modulation in vivo along the visual pathway to the superior colliculus, as measured by functional ultrasound imaging. The biosafety of the film was confirmed by the absence of short-term adverse effects under optical coherence tomography retinal imaging, while local thermal increases were measured below 1 °C. These findings demonstrate the potential of photoacoustic stimulation for high-acuity visual restoration over a large field of view in blind patients.

Performance investigations of the easily manufactured composite all-day radiative cooling materials based on PDMS

The passive radiative cooling technology can be employed to obtain the cooling capacity without any energy consumption, which has been garnering significant attention nowadays. This work proposes and experimentally studies the all-day radiative cooling material based on layered composite material made from Polydimethylsiloxane (PDMS). This work adds SiO2 nano-particles, which act as visible light scatters, and the proposed film can realize an excellent all-day cooling capacity when the thicknesses of the PDMS and Al films are respectively chosen as 200 μm and 4 μm, and the concentration of the SiO2 particles in the film is 40 %. The theoretical explorations indicated that the presented composite film can exhibit the high reflectivity (90.36 %) and emissivity (90.19 %) in the visible spectrum and atmospheric transparency window (ATW) spectrum. Under direct sunlight of a highest solar irradiance of 688.89 W/m2, there is an average temperature difference between cooling film and white paper of 6.3 °C. Furthermore, in clear weather conditions at night with an average humidity level of 58.15 %, it can generate a temperature difference of 4.8 °C. This work proposes an easily manufactured and eco-friendly all-day radiative cooling material, which has the potential applications in future refrigeration technology.

High-throughput and high-sensitive direct detection for pathogenic bacteria of urinary tract infections mediated by block-based design of flexible non-metallic composite SERS substrate

It remains a huge challenge to realize a high-throughput direct detection for pathogenic bacteria with high-sensitivity in practice. Here, we develop a typical two-dimensional (2D) composite semiconductor of BP@MoS2 with special synergistic chemical enhancement-mediated surface-enhanced Raman scattering (SERS) activity. The relative proportion of MoS2 and BP was rationally adjusted in the hydrothermal reaction to screen a composite sample with high charge transfer efficiency. Furthermore, the optimal BP@MoS2 nanocomposites were integrated with polydimethylsiloxane (PDMS) film based on a hydrophilic-hydrophobic scheme to improve the collection and on-site monitoring capability of SERS substrate. Unlike the conventional detection chip, this hydrophilic-hydrophobic model could facilitate the block design of active areas on the PDMS matrix, which was benefit for the high-throughput detection. More importantly, this SERS substrate was applied to directly monitor urinary tract pathogens of Escherichia coli, facilitating satisfactory recoveries between 90% and 110%. Overall, the as-proposed PDMS-BP@MoS2 SERS substrate exhibited advantages in the collection, quantification, and high-throughput fingerprint recognition of pathogenic bacteria, offering a new avenue for the clinical detection.

Influence of temperature and crack-tip speed on crack propagation in elastic solids.

I study the influence of temperature and the crack-tip velocity of bond breaking at the crack tip in rubber-like materials. Bond breaking is considered as a stress-aided thermally activated process and results in an effective crack propagation energy, which increases strongly with decreasing temperature or increasing crack-tip speed. This effect is particularly important for adhesive (interfacial) crack propagation but less important for cohesive (bulk) crack propagation owing to the much larger bond-breaking energies in the latter case. For adhesive cracks, the theory results are consistent with adhesion measurements for silicone rubber polydimethylsiloxane (PDMS) in contact with silica glass surfaces. For cohesive cracks, the theory agrees well with experimental results PDMS films chemically bound to silanized glass.

In-situ fabricated hexagonal PDMS microsphere arrays for substrate-mode light extraction in blue fluorescent organic light emitting diodes

To inhibit the total reflection in the substrate-mode light loss of organic light-emitting diodes (OLEDs) and fully take advantage of the excellent light converging and out-coupling effect of the hexagonal array of microsphere, we in-situ fabricated the hexagonal array of polydimethylsiloxane (PDMS) microsphere onto the substrate of OLEDs via the porous template for substrate-mode light extraction. Firstly, regular honeycomb porous polystyrene (PS) template was prepared via a self-assembly “breath figure” process. The PS molecular weight, solvent, and humidity play an important role on the uniformity of pore distribution and pore diameter according to Young-Laplace equation. Based on the optimized porous PS template, the PDMS microsphere array was fabricated by pattern transferring, which indicates more prominent light diffraction than the flat PDMS film. Finite-difference time-domain (FDTD) simulation denotes that higher duty ratio of the PDMS microsphere array contributes to higher light out-coupling efficiency. Therefore, a PDMS microsphere array with larger duty ratio of 84.0 % was applied in the extraction of external light for the blue fluorescent OLED device. The maximum luminance, current efficiency, and power efficiency are all improved, and the external quantum efficiency (EQE) is increased by 18.81 % with spectral stability.

Hyperbranched Thermosensitive Polymer-AuNP Composite Probe for Temperature Colorimetric Detection.

Temperature detection is particularly important in the medical and scientific fields. Although there are various temperature detection methods, most of them focus on broad temperature detection, and basic research in specific fields, especially the detection of subtle temperature changes (32-34 °C) during wound infection, is still insufficient. For this purpose, a novel colorimetric temperature sensing probe is designed in this paper, which can quickly and intuitively respond to small temperature changes within a specific range through color changes. In this paper, hyperbranched polyethyleneimine (HPEI) was modified by isobutyrylation to prepare hyperbranched temperature-sensitive polymer (HPEI-IBAm). And it was combined with gold nanoparticles (AuNPs) prepared by a sodium citrate reduction method to construct an HPEI-IBAm-AuNP colorimetric probe. The probe exhibits excellent stability, even at salt concentrations of up to 12 g/L, thanks to the abundant amino functional groups and the large steric hindrance effect unique to HPEI-IBAm. In particular, the temperature detection range of the probe is precisely locked within 32-34 °C, enabling it to respond quickly and accurately to small temperature changes of only 2 °C. This feature is perfectly suited to the practical needs of temperature detection in infected wounds. The linear fitting coefficient of the temperature response is as high as 0.9929, ensuring the accuracy of the test results. The detection performance of the probe remained highly consistent over 10 cycles, fully proving its excellent reusability and durability. In addition, a flexible colorimetric sensor was prepared by combining the probe with polydimethylsiloxane (PDMS) film. This sensor is capable of rapidly detecting human skin temperature in real time, achieving an accuracy of 99.07% to 100.61%. It can provide a possible solution to the challenges of delayed and difficult temperature detection caused by different body parts and uneven surfaces, among others. This demonstrates its extensive practical value and potential, and it is expected to be further applied in the monitoring of wound infections.

Enhancing Passive Radiative Cooling Films with Hollow Yttrium-Oxide Spheres Insights from FDTD Simulation.

Passive daytime radiative cooling (PDRC) presents a promising avenue for efficient thermal management without relying on electrical power. In this study, the potential of integrating Hollow Yttrium-Oxide Spheres (HYSs) within a Polydimethylsiloxane (PDMS) matrix to enhance PDRC is investigated. Through a combination of experimental characterization and computational analysis, the optical properties and radiative cooling performance of PDMS films embedded with HYSs are evaluated. These results demonstrate that HYSs significantly improve both solar reflectivity and long-wave infrared (LWIR) emissivity of the PDMS matrix. Finite-Difference Time-Domain (FDTD) simulations confirm the scattering efficiency of HYSs across various wavelength ranges, highlighting their effectiveness as additives for enhancing the radiative properties of passive cooling materials. Experimental validation reveals enhanced reflectivity and emissivity of PDMS films with embedded HYSs, resulting in superior cooling performance compared to non-HYS counterparts. Overall, this study underscores the potential of HYS-infused PDMS films as a promising solution for passive radiative cooling, with broad applicability in diverse domains requiring efficient thermal management solutions. Additionally, these research insights pave the way for establishing an AI database for passive radiative cooling research, offering new avenues for further exploration and application in this field.

Performance of microsphere-assisted imaging in bright-field and dark-field microscopy.

In this work, we study the imaging performance of microsphere-assisted microscopy (MAM) using microspheres with different refractive indices and immersion conditions under both bright-field illumination (BFI) and dark-field illumination (DFI). The experimental results show that the position of the photonic nanojet of the microsphere plays an important role in MAM imaging. The contrast in imaging is affected by the reflection from the microsphere, the background signal without the microsphere, and the electric field on the substrate surface. In MAM, BaTiO3 glass microspheres achieve better imaging results under BFI when immersed in a polydimethylsiloxane (PDMS) film but are challenging to image under DFI. However, SiO2 and polystyrene microspheres exhibit improved imaging performance under both BFI and DFI with PDMS-covered semi-immersion, and the imaging contrast in DFI is superior to that in BFI under the same conditions. Besides, the Talbot effect is observed by MAM under DFI when imaging 300-nm-diameter hexagonally close-packed nanoparticle arrays. This work reveals the advantage of MAM under DFI in improving the contrast.

Development of a Photothermal Regenerative Plasmonic Platform as a Light-Controlled Interface.

This study introduces a novel plasmonic nanocomposite platform, where gold nanoparticles (AuNPs) are synthesized in situ within a polydimethylsiloxane (PDMS) film. The innovative fabrication process leverages ethyl acetate swelling to achieve a uniform distribution of AuNPs, eliminating the need for additional reagents. The resulting nanocomposite film exhibits exceptional photothermal conversion capabilities, efficiently converting absorbed light into heat and rapidly reaching high temperatures. Furthermore, the platform is biofunctionalized with the phosphotriesterase enzyme, not only enabling the degradation of organophosphate pesticides but also showcasing the potential for multifunctional applications. The platform's ability to be regenerated after use underscores its sustainability for repeated applications.