Transparent Polydimethylsiloxane Research Articles

Mid-Infrared Photoacoustic Stimulation of Neurons through Vibrational Excitation in Polydimethylsiloxane.

Photoacoustic (PA) emitters are emerging ultrasound sources offering high spatial resolution and ease of miniaturization. Thus far, PA emitters rely on electronic transitions of absorbers embedded in an expansion matrix such as polydimethylsiloxane (PDMS). Here, it is shown that mid-infrared vibrational excitation of C─H bonds in a transparent PDMS film can lead to efficient mid-infrared photoacoustic conversion (MIPA). MIPA shows 37.5 times more efficient than the commonly used PA emitters based on carbon nanotubes embedded in PDMS. Successful neural stimulation through MIPA both in a wide field with a size up to a 100µm radius and in single-cell precision is achieved. Owing to the low heat conductivity of PDMS, less than a 0.5°C temperature increase is found on the surface of a PDMS film during successful neural stimulation, suggesting a non-thermal mechanism. MIPA emitters allow repetitive wide-field neural stimulation, opening up opportunities for high-throughput screening of mechano-sensitive ion channels and regulators.

Self-Cleaning Hydrophobic Coating Composed of Micro/Nano-Imprinted Polydimethylsiloxane with Enhanced Light In-Coupling Capabilities.

In this study, we have optimized optically transparent polydimethylsiloxane (PDMS) hydrophobic coating on glass substrates that exhibit self-cleaning as well as enhanced light in-coupling capabilities. Micro/nano textures on the surface of PDMS were introduced through micro/nanoimprinting to achieve light trapping as well as self-cleaning abilities. Comprehensive studies show that the periodic arrangement of the micro/nanopatterned features has enabled enhanced inward transmission of light in the visible range along with superior hydrophobicity. The water contact angle (WCA) measurements on these coatings demonstrated a superior capacity for self-cleaning with a WCA of about 117°. Subsequently, when these transparent and hydrophobic coatings were deposited on commercial silicon solar cells, they showed a 15.8% increment in efficiency due to enhanced light in-coupling with a nanopatterned PDMS coating.

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.

Optimization of Dielectric-Metal Multilayer Structure for Color-Preserving Radiative Cooling Window.

Radiative cooling window has been designed to emit infrared radiation in the atmospheric transparency window and reflects near-infrared light while allowing visible light to pass through. However, improvements are still needed in the transmissivity of visible light, the reflectivity of near-infrared light, and emissivity of mid-infrared spectra. This paper proposes a color-preserving radiative cooling window consisting of a multilayer film as a transparent near-infrared reflector and polydimethylsiloxane (PDMS) as a thermal emitter. This design involves optimizing the types of film materials, the number of layers, and the thicknesses of the films through a genetic algorithm. The performance of multilayer films with various layer numbers is compared, and we choose 7-layer multilayer film (Al2O3/Ag/Al2O3/Ag/Al2O3/Ag/Al2O3) as the transparent near-infrared reflector. Then, we analyze its spectral characteristics in depth. Sequentially, we place a 100-μm-thick PDMS as a thermal emitter above the transparent near-infrared reflector. By combining the transparent near-infrared reflector with the PDMS and utilizing genetic algorithm, a color-preserving radiative cooling window has been achieved with flat and broadband average visible transmittance (86%), high average near-infrared reflectance (86%), high average thermal emissivity (95%) in the atmospheric window, and the drop of temperature (22.3, 21.2, and 15.8 K when nonradiative heat coefficient is, respectively, 0, 6, and 12 W/m2/K).

Transparent PDMS Surfaces with Covalently Attached Lubricants for Enhanced Anti-adhesion Performance.

Liquid-like surfaces featuring slippery, omniphobic, covalently attached liquids (SOCALs) reduce unwanted adhesion by providing a molecularly smooth and slippery surface arising from the high mobility of the liquid chains. Such SOCALs are commonly prepared on hard substrates, such as glass, wafers, or metal oxides, despite the importance of nonpolar elastomeric substrates, such as polydimethylsiloxane (PDMS) in anti-fouling or nonstick applications. Compared to polar elastomers, hydrophobic PDMS elastomer activation and covalent functionalization are significantly more challenging, as PDMS tends to display fast hydrophobic recovery upon activation as well as superficial cracking. Through the extraction of excess PDMS oligomers and fine-tuning of plasma activation parameters, homogeneously functionalized PDMS with fluorinated polysiloxane brushes could be obtained while at the same time reducing crack formation. Polymer brush mobility was increased through the addition of a smaller molecular silane linker to exhibit enhanced dewetting properties and reduced substrate swelling compared to functionalizations featuring hydrocarbon functionalities. Linear polymer brushes were verified by thermogravimetric analysis. The optical properties of PDMS remained unaffected by the activation in high-frequency plasma but were impacted by low-frequency plasma. Drastic decreases in solid adhesion of not just complex contaminants but even ice could be shown in horizontal push tests, demonstrating the potential of SOCAL-functionalized PDMS surfaces for improved nonstick applications.

Simultaneous Optical and Electrical Monitoring of Charge Percolation in Flow Electrodes

Electrochemical reactions are limited to the surface of the electrode, which makes the construction and intensification of electrochemical processes challenging. To increase the space-time yield of electrochemical cells, the electrochemically active surface area has to be enlarged. This can be achieved by either increasing the surface of a fixed electrode (e.g., porous electrodes) or by so-called flow electrodes. Flow electrodes consist of conductive particles suspended in the electrolyte. They have the advantage of increasing the active surface area of the electrode and also enabling continuous recycling and exchange of the active electrode material. They have been successfully applied, for example, for energy storage in redox flow batteries and desalination in flow-electrode capacitive deionization (FCDI).In flow electrodes the conductive particles dynamically increase the active area of the electrode by collision with the electrode; however, the exact mechanism of charge transport in such suspensions, also called charge percolation, is not completely understood. Yet, the successful implementation of flow electrodes in electrochemical processes requires a deeper understanding of how these particles interact within the electrochemical system. Charge percolation in flow electrodes is highly dynamic, and the conductivity of the suspensions depends on multiple factors like the amount and position of the particles, the shape and accessibility of the current collector, and especially the contact between particles and current collector. Literature presents different approaches which deal with charge transport in conductive suspensions, either by analyzing the electrical properties of flow electrodes in flow or by examining the structure and position of the particles visually in static conditions. We combine visual and electrical in-situ monitoring of charge percolation events in a single experimental setup. We developed a transparent electrochemical flow cell, made of transparent polydimethylsiloxane (PDMS), allowing for in-situ measurements. A constant voltage is applied to the current collector by a potentiostat. The resulting electrical current is measured simultaneously by recoding the particle movements using an optical microscope and a high-speed camera. The design of the electrochemical cell enables different positions of the particles within the channel in different flow modes: Contact between particles and the current collector can be either prevented or enforced. A motion-tracking algorithm analyses the videos to determine the area of particles in the electric field and the area of particles contacting the current collector. This allows for the correlation of particle behavior and electrical current.We investigated the influence of electrolyte, particle fraction, and the contact probability of particles and current collector on charge transport. Our results show that contact between particles and the current collector is a main contributor to charge transport in flow electrodes. But particles cluster can also increase the current, even if they do not touch the current collectors. The highest increase in current was achieved for large particle fraction short circuiting both current collectors. These results show that the way the particle suspension interacts with the electrode and by guiding the flow the electrochemical processes can be improved dramatically.

Innovative, Flexible, and Miniaturized Microfluidic Paper-Based Plasmonic Chip for Efficient Near-Infrared Metal Enhanced Fluorescence Biosensing and Imaging.

The implementation of metal enhanced fluorescence (MEF) as an efficient detection tool, especially in the near-infrared region of the electromagnetic spectrum, is a rather new direction for diagnostic analytical technologies. In this context, we propose a novel microfluidic plasmonic design based on paper for efficient MEF detection of the "proof-of-concept" biotin-streptavidin recognition interaction. Our design made use of the benefits of gold nanobipyramids (AuBPs), considering the strong enhanced electromagnetic field present at their sharp tips, and filter paper to operate as a natural microfluidic channel due to excellent wicking abilities. The calligraphed plasmonic paper, obtained using a commercial pen filled with AuBPs, was integrated in a robust sandwich optically transparent polydimethylsiloxane chip, exhibiting portability and flexibility while preserving the chip's properties. To place the Alexa 680 fluorophore at an optimal distance from the nanobipyramid substrate, the human IgG-anti-IgG-conjugated biotin sandwich reaction was employed. Thus, upon the capture of Alexa 680-conjugated streptavidin by the biotinylated system, a 1.3-fold average enhancement of the fluorophore's emission was determined by bulk fluorescence measurements. However, the local enhancement factor was considerably higher with values spanning from 5 to 6.3, as proven by mapping the fluorescence emission under both re-scan microscopy and fluorescence lifetime imaging, endorsing the proposed chip's feasibility for bulk MEF biosensing as well as high-resolution MEF bioimaging. Finally, the versatility of our chip was demonstrated by adapting the biosensing protocol for cardiac troponin I biomarker detection, validated using 10 plasma samples collected from pediatric patients and corroborated with a conventional ELISA assay.

Enhanced light extraction for red organic light emitting diodes via PDMS convex lens based on breath figure method

To inhibit the light loss of substrate mode at the substrate/air interface in organic light emitting diodes (OLEDs), regular porous polystyrene (PS) template was fabricated via the “Breath figure” method. The structure of porous mold was optimized by adjusting the PS solution concentration from 10 to 60 mg/ml and relative humidity from 60% to 80%. The optimal porous PS mold was achieved at 50 mg/ml PS solution under 70% relative humidity. Then, elastic micro-lens arrays based on transparent elastomer polydimethylsiloxane (PDMS) were obtained via a two-step transferring process from the porous PS mold. The projection experiment exhibits excellent focusing effect of the PDMS convex lens relative to the planar PDMS film. These PDMS micro-lens films were in situ fabricated onto the external face of the red OLED device to extract substrate mode light. By using the PDMS micro-lens array with a height of 1.2 μm and a diameter of 6.7 μm, the OLED device demonstrates an enhancement of 32.7%, 35.6%, 46.5%, and 27.6% for maximum luminance, current efficiency, power efficiency, and external quantum efficiency, respectively, without changing its color purity. The device with PDMS micro-lens exhibits a higher intensity than an ideal Lambertian emission pattern, especially at viewing angles from 30° to 60°. It suggests that the introduction of external micro-lens structure significantly improves the light outcoupling efficiency.

A multifunctional non‐fluorinated flame retardant superhydrophobic 3‐D porous material for highly selective oil spill treatment and removal of dyes

AbstractThe environment and global healthcare are at risk from oily wastewater accumulation and spills. Hence, porous sponge materials are widely sought for remedial oil cleanups. Materials with superhydrophobic and photocatalytic characteristics are implemented for extensive use besides oil–water separation, self‐cleaning, and removal of dyes. Regardless of the various upsides, few materials display both of these features jointly. Most nanomaterial photocatalysts are susceptible to the action of ultraviolet (UV) light irradiation, which often inhibits their hydrophobicity. Here in this work, a photocatalyst such as ZnO was coated on a porous 3‐D melamine sponge (MS). To preserve the hydrophobicity without sacrificing the photocatalytic behavior, ZnO coated melamine sponge was modified with transparent polydimethylsiloxane (PDMS) to obtain MS/ZnO/PDMS. The obtained superhydrophobic photocatalytic sponge exhibits exceptional oil adsorption capacity, superior stability even under severe conditions and the ability to remove organic dyes. Remarkably, the sponge exhibits outstanding compressive strength and fire resistance properties, indicating the possible utilization in a prolonged practical execution. As a result, this technique might pave the way for the creation of a comprehensive design for an improved superhydrophobic photocatalytic sponge with high stability and recyclability.

Plasmon mediated extra-ordinary optical transmission through an apertureless plasmonic metagrating

Extra-ordinary optical transmission (EOT) through subwavelength plasmonic nanoapertures is possible due to the funneling of light via surface plasmons (SPs) at the resonant wavelengths through the apertures. In this Letter, we experimentally demonstrate EOT through a plasmonic metagrating which does not have any open apertures. The plasmonic metagrating was fabricated by deposition of silver (Ag) on a one-dimensionally patterned flexible and transparent polydimethylsiloxane grating obtained via pattern imprinting and subsequent peeling off a commercially available blue ray disk. For normal incidence of transverse magnetic-polarized light on the top surface of plasmonic metagrating, transmission of light through it was obtained in the visible wavelength range of electromagnetic spectrum. Control experiments on variation of Ag film thickness were performed to attain optimal parameters for maximum transmission, followed by polarization and refractive index (RI) dependent performance of the plasmonic metagrating. Electric fields and Poynting vector profiles were simulated using a finite element method to explain the interaction of light with the plasmonic metagrating and the mechanism of plasmon mediated optical transmission. Such a large optical transmission is possible because the SP modes generated at metal–air interface penetrate through metagrating and couple with those supported by the metal–substrate interface. As a model application, RI sensing using the plasmonic metagrating was demonstrated. The present study shows that optical transmission is possible from apertureless structures and enriches literature with better understanding of EOT. Moreover, it opens avenues for development of flexible, cost-effective plasmonic metagratings for sensors, spectral filters, polarizers, etc.

Transparent microfiber Fabry-Perot ultrasound sensor with needle-shaped focus for multiscale photoacoustic imaging

Photoacoustic tomography emerged as a promising tool for noninvasive biomedical imaging and diseases diagnosis. However, most of the current piezoelectric ultrasound transducers suffer optical opacity and tissue-mismatched acoustic impedance, hindering the miniaturization and integration of the system for multiscale and multimodal imaging. Here, a transparent polydimethylsiloxane (PDMS) encapsulated optical microfiber ultrasound sensor was demonstrated for photoacoustic imaging with scalable spatial resolution and penetration depth. The sensor comprised a microfiber loop sandwiched by a pair of in-line Bragg gratings, which formed an ultrasound-sensitive Fabry-Perot cavity allowing free delivery of ultrasound/light beams and unique needle-shaped ultrasound focusing along the penetration depth. The sensor with a detection limit of ∼ 700 Pa and a bandwidth of ∼ 10 MHz was applied for multiscale photoacoustic imaging of mouse ear and brain vasculatures. With advantages of flexibility, optical transparence and focusing capability, the sensor offers new opportunities for developing photoacoustic/ultrasound imaging devices for biomedical and clinic applications.

Penetration Coefficients of Commercial Nanolimes and a Liquid Mineral Precursor for Pore-Imitating Test Systems—Predictability of Infiltration Behavior

Nanolimes have been commercially available for over a decade as a remineralization agent for natural stone to combat deterioration. While they have been applied successfully and studied extensively, their penetration abilities in different materials have not yet been readily quantifiable in situ and in real time. Using two transparent pore-imitating test systems (acrylic glass (PMMA) and polydimethylsiloxane (PDMS)) and light microscopy, the penetration coefficients (PCs) of two nanolimes (CaLoSiL (CLS) and Nanorestore Plus (NRP)), as well as their solvents, were determined experimentally in square channels of about 100 µm diameter. Their PCs and those for a previously published glass-resin-based test system were also predicted based on measurable material parameters or literature values using the Lucas-Washburn equation. Additionally, a liquid mineral precursor (LMP) of calcium carbonate based on complex coacervation (CC) was investigated as an alternative to the solid particle dispersions of nanolime. In general, the dispersions behaved like their pure solvents. Overall, trends could be reasonably well predicted with both literature and experimentally determined properties using the Lucas-Washburn equation. In absolute terms, the prediction of observed infiltration behavior was satisfactory for alcohols and nanolimes but deviated substantially for water and the aqueous LMP. The commercially available PMMA chips and newly designed PDMS devices were mostly superior to the previously published glass-resin-based test system, except for the long-term monitoring of material deposition. Lastly, the transfer of results from these investigated systems to a different, nontransparent mineral, calcite, yielded similar PC values independently of the original data when used as the basis for the conversion (all PC types and all material/liquid combinations except aqueous solutions in PDMS devices). This knowledge can be used to improve the targeted design of tailor-made remineralization treatments for different application cases by guiding solvent choice, and to reduce destructive sampling by providing a micromodel for pretesting, if transferability to real stone samples proves demonstrable in the future.

ProtoHand: Solderless Prototyping of Electrical Circuits on a Soft Artificial Hand with Liquid Metal

In this letter, we propose and demonstrate ProtoHand, which is a soft artificial hand that can work as a universal platform for prototyping electrical circuits similar to a breadboard. ProtoHand is made of flexible and transparent polydimethyl siloxane. ProtoHand has multiple channels filled with liquid metal beneath the surface, like the blood vessels of a hand. Electric components, such as resistors and capacitors, can be inserted by piercing into ProtoHand and electrically connected via the conductive liquid metal. Soldering is unnecessary, and the parts can be removed without leakage of the liquid metal; therefore, prototyping of electric circuits can be performed on this soft hand in a reusable manner. ProtoHand will help the design of multifunctional robot hands and could also be an excellent educational tool.

Hierarchically Nanostructured Janus Membranes Toward Sustainable and Efficient Solar‐to‐Thermal Management

AbstractSolar‐enabled thermal management is emerging as a promising candidate to exploit green, low‐cost and efficient heat‐related applications, which has drawn extensive intensity for the development of solar‐to‐thermal materials with high‐performance and desirable functionality. However, there still remain considerable challenges, such as the sharp temperature fluctuations under water‐related environment, high cost, complex fabrication approaches and limited energy efficiency. Here, superhydrophobic and photothermal nanostructured Janus membranes composed of hierarchical candle soot and transparent polydimethylsiloxane is proposed in a simple, low‐cost, and effective way. The achieved membranes can readily adapt to curved surfaces and enable efficient solar‐to‐thermal capability of ≈68 °C under 1 sun and good water‐repellant property of ≈159.7. Therefore, it can still maintain stable temperature without remarkable temperature decline when exposed to the high‐moisture environment. Also, the asymmetric structure can further endow the membrane with declined heat dissipation for high‐performance thermal management. Moreover, it can further function as a self‐supported agricultural film to continuously heat the soils with stable temperature for efficient bean growth, demonstrating significant potential in the new generation of urban agriculture.

Assembling graphene aerogel hollow fibres for solar steam generation

Solar vapor generation, a cost-effective way to harvest solar energy for purifying polluted or saline water, has attracted great attention in recent years. However, during the harsh environment (e.g. high-salinity brine), challenges still remain in limited water evaporation, complicated/compromised systems between water transport, evapor area and salt accumulation. Herein, graphene aerogel hollow fibers (GAHF) are developed and assembled into a solar steam generator which demonstrates exceptionally high efficiency for water evaporation and salt rejection under sun irradiation. Inspired from the capillary water transportation system in trees, the mesophase-ordered GAHFs are spun from their liquid crystalline suspension, and subsequently assembled into a roll of unidirectionally aligned bundles and then embedded in a transparent polydimethylsiloxane (PDMS) matrix. The synergistic effects between GAHFs, serving as 1D-confining micro-channels for water transport and broadband solar absorbers, and PDMS matrix, as an light refractor and “canyons”-like evaporation area, improve the water flow and absorption of solar energy and maximize the evaporation surface area. As a result, the GAHF arrays expedite remarkable transpiration, achieving continuous steam generation (∼3.29 kg m−2 h−1) and outstanding salt-rejection performance for high-salinity brine (e.g. saturated solution) desalination. This GAHF based solar steam generation system provides a facile and high-performance device for self-generating seawater desalination.

The largest aluminum molecular rings: Phenol‐thermal synthesis, photoluminescence, and optical limiting

AbstractIt is of great interest to modulate the photophysical properties by atomically precise chemical control. The incorporation of conjugated ligands into crystalline materials provides a platform for molecular‐level interpretation of the structure‐activity relationship. Herein, we reported the phenol‐thermal and scale‐up synthesis of a new family of remarkably stable aluminum molecular rings. They are assembled by twenty AlIII ions with large conjugated ligands and phenols, representing the currently largest sizes (up to 4 nm in diameter) in the field of main group metal oxo clusters. Phenols are not only reaction medium but also auxiliary bridging ligands on the surface of macrocyclic molecules. In addition, they are either parallel to the center of the molecular ring or inserted into the molecular ring, or form dimers/tetramers that bind macrocyclic molecules to form supramolecular structures. These macrocyclic rings are hydrophobic and ultra‐stable, evidenced by retaining their morphology and crystalline when exposed to air for more than a year. Compared with the pristine conjugated ligands, they exhibit coordination‐enhanced fluorescence. By dispersing them into a polydimethylsiloxane (PDMS) matrix, we prepared transparent and flexible PDMS thin films for coupling flexible display and nonlinear optical application. Our discovery of such atomically precise rings provides a platform for the fine‐tuning of photo‐related performances.

Behavior of Cell Flowing Over Oblique Microrectangular Groove

Abstract Is it possible to distinguish cells with minimally invasive methods according to the characteristics of cells when moving through flow paths in vitro? A microflow-channel with microgrooves 45 deg diagonal to the mainstream direction has been manufactured by photolithography technology. The flow path between the two transparent polydimethylsiloxane disks (0.05 mm high, 1 mm wide, and 25 mm long) has rectangular microgrooves (4.5 μm deep, 0.2 mm long) at the bottom with variations in groove widths (0.03 mm, 0.04 mm, and 0.05 mm). Deformation and orientation of floating mouse-myoblasts (C2C12) during passage over the microgrooves were measured. Experimental results show that the larger the shape change of the two-dimensional projected image in the groove, the smaller the angle change tends to be. This method may be applicable to classification by cell deformation.

Stretchable Optical Diffuser Constructed by Alternate Procedure of Interfacial Complexation and Thermal Crosslinking.

Stretchable optical diffuser is an indispensable photon management element in wearable display devices. Herein, a novel optical diffuser constructed by interfacial hydrogen bonding complexation of methylcellulose (MC), poly(ethylene oxide) (PEO), and polymer complex nanoparticles (PCNP) on transparent polydimethylsiloxane (PDMS) substrate is proposed. The introduction of PEO can toughen the complex film and endow the coating with stretchability. With proper thermal treatment, the polymer complex can be crosslinked through esterification which shows an improved optical diffusion performance and durability. The optimized film exhibits 92% of transmittance (T), 93% of haze (H), and 73% of elongation. It also presents a desirable optical diffusion effect about 88% of T and 93% of H in the stretching state. Moreover, the resulting complex film shows excellent anti-fatigue capacity which maintains 90% of T and 90% of H after 10000 stretching cycles. The reported polymer complex film broadens the application of interfacial complexation and demonstrates potential to apply in the integrated wearable optical devices.

A transparent ultra-broadband microwave absorber based on flexible multilayer structure

In this work, a transparent ultra-broadband microwave absorber (MA) based on flexible multilayer structure was demonstrated. The designed resonant structure consists of a resistive film pattern of indium tin oxide (ITO) on a flexible substrate PET. By adjusting the size of the resonant layer ITO pattern and the array position arrangement, an ultra-broadband absorption of over 90% is achieved in the frequency range 8.6–75.8 GHz, with a relative absorption bandwidth of 159%. At the same time, the transparent flexible medium polydimethy-lsiloxane (PDMS) and PET substrate are used to obtain good optical transmittance. Due to the quadruple symmetry of the resistive film resonance pattern, MA shows high polarization insensitivity. For TE and TM polarised waves, the proposed MA can maintain an absorption rate greater than 80% as the angle of incidence is increased to 40°. The current distribution of each resonant layer at strong resonant frequency is simulated and analysed to determine the absorption mechanism of MA. A sample consisting of 11 × 11 cells was produced and the experimental measurements were in general consistent with the numerical simulation results. Due to its ultra-wideband absorption characteristics and wide incident angle stability, it has potential application value in the fields of radar stealth system and transparent electromagnetic shielding.

Ice adhesion properties of periodic surface microtextured optically transparent superhydrophobic polydimethylsiloxane

There is a need for optically transparent surfaces which repel water and eliminate ice formation in applications, such as solar power generation. Surface microtexture has played an important role in controlling wetting properties and ice adhesion pressure. Here we report the effect of periodic surface microtexture on water wetting properties and ice adhesion pressure for optically transparent Polydimethylsiloxane. Laser ablation was used to produce surface microtexture on an aluminum substrate and was transferred onto a polydimethylsiloxane (PDMS) surface via hot embossing. The control of laser processing patterns with smooth area from 53.8% to 89.6% enabled fine-tuning of the wetting and ice adhesion properties. PDMS with a grid microtexture pattern has proven to be superhydrophobic and exhibited an ice adhesion pressure as low as 60.1 kPa, allowing the achievement of a water repellent and anti-icing surface. The surface wetting and anti-icing properties of the microtextured surfaces were quantified by the measurement of the receding contact angle (RCA), contact angle hysteresis (CAH), and ice adhesion pressure. Various publications have pointed to the ROA, RCA, or CAH as a predictor of low ice adhesion pressures for smooth surfaces. For microtextured surfaces, it was found that the CAH was the most accurate predictor of ice adhesion pressure.