A Versatile Strategy for Concurrent Passive Daytime Radiative Cooling and Sustainable Energy Harvesting.

Developing versatile systems that can concurrently achieve energy saving and energy generation is critical to accelerate carbon neutrality. However, challenges on designing highly effective, large scale, and multifunctional photonic film hinder the concurrent combination of passive daytime radiative cooling (PDRC) and utilization of sustainable clean energies. Herein, a versatile scalable photonic film (Ecoflex@h-BN) with washable property and excellent mechanical stability is developed by combining the excellent scattering efficiency of the hexagonal boron nitride (h-BN) nanoplates with the high infrared emissivity and ideal triboelectric negative property of the Ecoflex matrix. Strikingly, sufficiently high solar reflectance (0.92) and ideal emissivity (0.97) endow the Ecoflex@h-BN film with subambient cooling effect of ≈9.5 °C at midday during the continuous outdoor measurements. In addition, the PDRC Ecoflex@h-BN film-based triboelectric nanogenerator (PDRC-TENG) exhibits a maximum peak power density of 0.5 W m-2 . By reasonable structure design, the PDRC-TENG accomplishes effective wind energy harvesting and can successfully drive the electronic device. Meanwhile, an on-skin PDRC-TENG is fabricated to harvest human motion energy and monitor moving states. This research provides a novel design of a multifunctional PDRC photonic film, and offers a versatile strategy to realize concurrent PDRC and sustainable energies harvesting.

A Highly Sensitive and Stretchable Core-Shell Fiber Sensor for Gesture Recognition and Surface Pressure Distribution Monitoring.

This work reports a highly-strain flexible fiber sensor with a core-shell structure utilizes a unique swelling diffusion technique to infiltrate carbon nanotubes (CNTs) into the surface layer of Ecoflex fibers. Compared with traditional blended Ecoflex/CNTs fibers, this manufacturing process ensures that the sensor maintains the mechanical properties (923% strain) of the Ecoflex fiber while also improving sensitivity (gauge factor is up to 3716). By adjusting the penetration time during fabrication, the sensor can be customized for different uses. As an application demonstration, the fiber sensor is integrated into the glove to develop a wearable gesture language recognition system with high sensitivity and precision. Additionally, the authors successfully monitor the pressure distribution on the curved surface of a soccer ball by winding the fiber sensor along the ball's surface.

Flexible Ecoflex®/Graphene Nanoplatelet Foams for Highly Sensitive Low-Pressure Sensors.

The high demand for multifunctional devices for smart clothing applications, human motion detection, soft robotics, and artificial electronic skins has encouraged researchers to develop new high-performance flexible sensors. In this work, we fabricated and tested new 3D squeezable Ecoflex® open cell foams loaded with different concentrations of graphene nanoplatelets (GNPs) in order to obtain lightweight, soft, and cost-effective piezoresistive sensors with high sensitivity in a low-pressure regime. We analyzed the morphology of the produced materials and characterized both the mechanical and piezoresistive response of samples through quasi-static cyclic compression tests. Results indicated that sensors infiltrated with 1 mg of ethanol/GNP solution with a GNP concentration of 3 mg/mL were more sensitive and stable compared to those infiltrated with the same amount of ethanol/GNP solution but with a lower GNP concentration. The electromechanical response of the sensors showed a negative piezoresistive behavior up to ~10 kPa and an opposite trend for the 10-40 kPa range. The sensors were particularly sensitive at very low deformations, thus obtaining a maximum sensitivity of 0.28 kPa-1 for pressures lower than 10 kPa.

A Batteryless, Wireless Strain Sensor Using Resonant Frequency Modulation.

In this study, we demonstrated the feasibility of a wireless strain sensor using resonant frequency modulation through tensile impedance test and wireless sensing test. To achieve a high stretchability, the sensor was fabricated by embedding a copper wire with high conductivity in a silicone rubber with high stretchability, in which the resonant frequency can be modulated according to changes in strain. The characteristics of the sensor and the behavior of wireless sensing were calculated based on equations and simulated using finite element method. As the strain of the sensor increased, the inductance increased, resulting in the modulation of resonant frequency. In experimental measurement, as the strain of the sensor increased from 0% to 110%, its inductance was increased from 192 nH to 220 nH, changed by 14.5%, and the resonant frequency was shifted from 13.56 MHz to 12.72 MHz, decreased by 6.2%. It was demonstrated that using the proposed sensor, strains up to 110% could be detected wirelessly up to a few centimeters.

Stretchable Complementary Split Ring Resonator (CSRR)-Based Radio Frequency (RF) Sensor for Strain Direction and Level Detection.

In this paper, we proposed a stretchable radio frequency (RF) sensor to detect strain direction and level. The stretchable sensor is composed of two complementary split ring resonators (CSRR) with microfluidic channels. In order to achieve stretchability, liquid metal (eutectic gallium-indium, EGaIn) and Ecoflex substrate are used. Microfluidic channels are built by Ecoflex elastomer and microfluidic channel frames. A three-dimensional (3D) printer is used for fabrication of microfluidic channel frames. Two CSRR resonators are designed to resonate 2.03 GHz and 3.68 GHz. When the proposed sensor is stretched from 0 to 8 mm along the +x direction, the resonant frequency is shifted from 3.68 GHz to 3.13 GHz. When the proposed sensor is stretched from 0 to 8 mm along the -x direction, the resonant frequency is shifted from 2.03 GHz to 1.78 GHz. Therefore, we can detect stretched length and direction from independent variation of two resonant frequencies.

Flexible Microfluidic Strain Sensor Made with Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-MXene-Au Nanocomposites for Monitoring Physiological Signals.

Flexible strain sensors have been widely used in wearable electronics. However, the fabrication of flexible strain sensors with a large strain detection range, high sensitivity, and negligible hysteresis remains a formidable challenge, even after enormous advancements in the field. Herein, a flexible microfluidic strain sensor was fabricated by filling poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-MXene-gold (PEDOT:PSS-MXene-Au) nanocomposites into microchannels in an elastic matrix. Owing to the unique properties of the nanofiller and Ecoflex elastomer microchannel, the microfluidic strain sensor detected a strain of 0%-500% with low hysteresis (2.4%), high sensitivity (guage factor = 25.4), short response times (∼86 ms), and good durability. Moreover, the flexible microfluidic sensor was used to detect various physiological signals and human activities, control a mechanical hand, and capture hand motions in real time. As demonstrated by its good performance, the proposed flexible microfluidic sensor holds great potential in applications such as wearable electronics, physiological signal monitoring and human-machine interactions.

A Multiaxial Fracture of Ecoflex Skin with Different Shore Hardness for Morphing Wing Application.

The use of elastomer-based skins in morphing wings has become increasingly popular due to their remarkable stretchability and mechanical properties. However, the possibility of the skin fracturing during multiaxial stretching remains a significant design challenge. The propagation of cracks originating from flaws or notches in the skin can lead to the specimen breaking into two parts. This paper presents an experimental study aimed at comprehensively evaluating crack propagation direction, stretchability, and fracture toughness of silicone-based elastomeric skin (Ecoflex) for morphing wing applications, using varying Shore hardness values (10, 30, and 50). The findings show that the lower Shore hardness value of 10 exhibits a unique Sideways crack propagation characteristic, which is ideal for morphing skins due to its high stretchability, low actuation load, and high fracture toughness. The study also reveals that the Ecoflex 10 is suitable for use in span morphing, with a fracture toughness of approximately 1.1 kJ/m2 for all thicknesses at a slower strain rate of 0.4 mm/min. Overall, this work highlights the superior properties of Ecoflex 10 and its potential use as a morphing skin material, offering a groundbreaking solution to the challenges faced in this field.

The Influence of Industrial Environmental Factors on Soft Robot Materials.

This work aims to identify the effects that a series of environmental factors, specific to the industrial conditions, have on the materials in the structure of soft robots and, therefore, on soft robotics systems. The purpose is to understand the changes in the mechanical characteristics of silicone materials, with the aim of transferring soft robotics applications from the sphere of services in the industrial field. Distilled water, hydraulic oil, cooling oil, and UV rays are the environmental factors considered in which the specimens were immersed/exposed for 24 h according to ISO-62/2008. The analysis was carried out on two of the most widely used materials in the field, belonging to the category of silicone rubber, which were subjected to uniaxial tensile tests on the strength testing machine Titan 2 Universal. The results show that the greatest impact on the characteristics of the two materials was when exposed to UV rays, while the other media tested had relatively little impact on the mechanical and elastic properties (tensile strength, elongation at break, and tensile modulus) of these materials.

Hybrid Pressure Sensor Based on Carbon Nano-Onions and Hierarchical Microstructures with Synergistic Enhancement Mechanism for Multi-Parameter Sleep Monitoring.

With the existing pressure sensors, it is difficult to achieve the unification of wide pressure response range and high sensitivity. Furthermore, the preparation of pressure sensors with excellent performance for sleep health monitoring has become a research difficulty. In this paper, based on material and microstructure synergistic enhancement mechanism, a hybrid pressure sensor (HPS) integrating triboelectric pressure sensor (TPS) and piezoelectric pressure sensor (PPS) is proposed. For the TPS, a simple, low-cost, and structurally controllable microstructure preparation method is proposed in order to investigate the effect of carbon nano-onions (CNOs) and hierarchical composite microstructures on the electrical properties of CNOs@Ecoflex. The PPS is used to broaden the pressure response range and reduce the pressure detection limit of HPS. It has been experimentally demonstrated that the HPS has a high sensitivity of 2.46 V/104 Pa (50-600 kPa) and a wide response range of up to 1200 kPa. Moreover, the HPS has a low detection limit (10 kPa), a high stability (over 100,000 cycles), and a fast response time. The sleep monitoring system constructed based on HPS shows remarkable performance in breathing state recognition and sleeping posture supervisory control, which will exhibit enormous potential in areas such as sleep health monitoring and potential disease prediction.

Influence of Calcium Carbonate Nanoparticles on the Soil Burial Degradation of Polybutyleneadipate-Co-Butylenetherephthalate Films.

A polybutyleneadipate-co-butylenetherephthalate (PBAT) sample, commercially known as Ecoflex®, was processed via melt extrusion with CaCO3 nanoparticles coated with a hydrophobic coating. Blown films of PBAT and two composites with nanofiller (2% and 5%wt) were prepared and degradation tests in soil at 30 °C up to 180 days were carried out with weight loss measurements. Furthermore, biodegradation test according to ISO 14851 was carried out at 30 °C. The effect of CaCO3 on soil burial degradation was assessed by surface wettability and SEM. ATR-FTIR and XPS analyses highlighted chemical modifications induced by soil degradation. CaCO3 nanoparticles decreased surface wettability and discouraged the disintegration in soil. Interestingly, SEM images after soil degradation highlighted in the nanocomposite films selective zones of disintegration. XPS showed an increasing peak area C 1s ratio of C-O to C=O with degradation time. Moreover, after the soil burial test, carbonyl index determined by ATR-FTIR increased in both nanocomposites. In fact, the addition of CaCO3 leads to a rise in the carbonyl zone due to the presence of the carbonate group. Remarkably, FTIR data after soil degradation showed an enrichment of the aromatic content, a preferential cleavage and erosion of the aliphatic moiety in PBAT films, amplified by the presence of the CaCO3 nanofiller.

Highly Stretchable Sensor Based on Fluid Dynamics-Assisted Graphene Inks for Real-Time Monitoring of Sweat.

Graphene inks have recently attracted attention for the development of printed wearable and flexible electronics and sensors not only because of their high conductivity and low cost but also because they are suitable for high-speed printing. Although reliable and scalable printing technologies are well established, further improvement in graphene inks in terms of electrical conductivity, stretchability/flexibility, and mass production is necessary for sensors for real-time monitoring. Herein, highly stretchable and conductive graphene inks were prepared by an efficient and scalable fluid dynamics-assisted exfoliation of graphite and a mixing process with elastomeric Ecoflex. After printing inks onto textile substrates, the serpentine-patterned conductors exhibited high conductivity and stable resistance even under a mechanically stretched state (a strain of 150%). Electrochemical sensors that detect sodium ions were fabricated on this conducting platform. These sensors indicated high potentiometric sensing ability under different mechanical deformations. To demonstrate the on-body performance of the developed sensors, real-time monitoring of sodium-ion concentration in the sweat of a human subject was carried out during an indoor stationary cycling exercise.

Soft Gripper with Electro-Thermally Driven Artificial Fingers Made of Tri-layer Polymers and a Dry Adhesive Surface.

Soft grippers have attracted great interest in the soft robotics research field. Due to their lack of deformability and control over compliance, it can be challenging for them to pick up objects that are too large or too small in size. In particular, compliant objects are vulnerable to the large grasping force. Therefore, it is crucial to be able to adjust the stiffness of the gripper materials. In this study, a soft gripper consisting of three artificial fingers is reported on. Each of the artificial fingers is made of a tri-layer polymer structure. An exterior layer, made of an ecoflex-graphene composite is embedded with electric wires as a heating source, by applying direct-current potential. The Joule heat not only allows for deformation of the exterior layer, but also transfers heat to the middle layer of the thermoplastic polyurethane (TPU) elastomer. As a result, the stiffness of the TPU layer can be adjusted using electro-thermal heating. Meanwhile, the third layer consists of a polydimethylsiloxane replica as a supporting layer with a gecko-inspired dry adhesive structure. By applying voltage through electric wires, the artificial fingers can bend and, thus, the soft gripper can hold the objects, with the help of the dry adhesive layer. Finally, objects like a shuttlecock, tennis ball and a glass beaker, can be picked up by the soft gripper. This research may provide an insight for the design and fabrication of soft robotic manipulators.

Comparison of the Dielectric Properties of Ecoflex® with L,D-Poly(Lactic Acid) or Polycaprolactone in the Presence of SWCN or 5CB.

The main goal of this paper was to study the dielectric properties of hybrid binary and ternary composites based on biodegradable polymer Ecoflex®, single walled carbon nanotubes (SWCN), and liquid crystalline 4'-pentyl-4-biphenylcarbonitrile (5CB) compound. The obtained results were compared with other created analogically to Ecoflex®, hybrid layers based on biodegradable polymers such as L,D-polylactide (L,D-PLA) and polycaprolactone (PCL). Frequency domain dielectric spectroscopy (FDDS) results were analyzed taking into consideration the amount of SWCN, frequency, and temperature. For pure Ecoflex®, two relaxation processes (α and ß) were identified. It was shown that the SWCN admixture (in the weight ratio 10:0.01) did not change the properties of the Ecoflex® layer, while in the case of PCL and L,D-PLA, the layers became conductive. The dielectric constant increased with an increase in the content of SWCN in the Ecoflex® matrix and the conductive behavior was not visible, even for the greatest concentration (10:0.06 weight ratio). In the case of the Ecoflex® polymer matrix, the conduction relaxation process at a frequency ca. several kilohertz appeared and became stronger with an increase in the SWCN admixture in the matrix. Addition of oleic acid to the polymer matrix had a smaller effect on the increase in the dielectric response than the addition of liquid crystal 5CB. Fourier transform infrared (FTIR) results revealed that the molecular structure and chemical character of the Ecoflex® and PCL matrixes remained unchanged upon the addition of SWCN or 5CB in a weight ratio of 10:0.01 and 10:1, respectively, while molecular interactions appeared between L,D-PLA and 5CB. Moreover, adding oleic acid to pure Ecoflex® as well as the binary and ternary hybrid layers with SWCN and/or 5CB in a weight ratio of Ecoflex®:oleic acid equal to 10:0.3 did not have an influence on the chemical bonding of these materials.

Flexible Wireless Passive LC Pressure Sensor with Design Methodology and Cost-Effective Preparation.

Continuous monitoring of physical motion, which can be successfully achieved via a wireless flexible wearable electronic device, is essential for people to ensure the appropriate level of exercise. Currently, most of the flexible LC pressure sensors have low sensitivity because of the high Young's modulus of the dielectric properties (such as PDMS) and the inflexible polymer films (as the substrate of the sensors), which don't have excellent stretchability to conform to arbitrarily curved and moving surfaces such as joints. In the LC sensing system, the metal rings, as the traditional readout device, are difficult to meet the needs of the portable readout device for the integrated and planar readout antenna. In order to improve the pressure sensitivity of the sensor, the Ecoflex microcolumn used as the dielectric of the capacitive pressure sensor was prepared by using a metal mold copying method. The Ecoflex elastomer substrates enhanced the levels of conformability, which offered improved capabilities to establish intimate contact with the curved and moving surfaces of the skin. The pressure was applied to the sensor by weights, and the resonance frequency curves of the sensor under different pressures were obtained by the readout device connected to the vector network analyzer. The experimental results show that resonant frequency decreases linearly with the increase of applied pressure in a range of 0-23,760 Pa with a high sensitivity of -2.2 MHz/KPa. We designed a coplanar waveguide-fed monopole antenna used to read the information of the LC sensor, which has the potential to be integrated with RF signal processing circuits as a portable readout device and a higher vertical readout distance (up to 4 cm) than the copper ring. The flexible LC pressure sensor can be attached to the skin conformally and is sensitive to limb bending and facial muscle movements. Therefore, it has the potential to be integrated as a body sensor network that can be used to monitor physical motion.

Metal-Free Multilayer Hybrid PENG Based on Soft Electrospun/-Sprayed Membranes with Cardanol Additive for Harvesting Energy from Surgical Face Masks.

Disposable surgical face masks are usually used by medical/nurse staff but the current Covid-19 pandemic has caused their massive use by many people. Being worn closely attached to the people's face, they are continuously subjected to routine movements, i.e., facial expressions, breathing, and talking. These motional forces represent an unusual source of wasted mechanical energy that can be rather harvested by electromechanical transducers and exploited to power mask-integrated sensors. Typically, piezoelectric and triboelectric nanogenerators are exploited to this aim; however, most of the current devices are too thick or wide, not really conformable, and affected by humidity, which make them hardly embeddable in a mask, in contact with skin. Different from recent attempts to fabricate smart energy-harvesting cloth masks, in this work, a wearable energy harvester is rather enclosed in the mask and can be reused and not disposed. The device is a metal-free hybrid piezoelectric nanogenerator (hPENG) based on soft biocompatible materials. In particular, poly(vinylidene fluoride) (PVDF) membranes in the pure form and with a biobased plasticizer (cardanol oil, CA) are electrospun onto a laser-ablated polyimide flexible substrate attached on a skin-conformable elastomeric blend of poly(dimethylsiloxane) (PDMS) and Ecoflex. The multilayer structure of the device harnesses the piezoelectricity of the PVDF nanofibers and the friction triboelectric effects. The ultrasensitive mechanoelectrical transduction properties of the composite device are determined by the strong electrostatic behavior of the membranes and the plasticization effect of cardanol. In addition, encapsulation based on PVDF, PDMS, CA, and parylene C is used, allowing the hPENG to exhibit optimal reliability and resistance against the wet and warm atmosphere around the face mask. The proposed device reveals potential applications for the future development of smart masks with coupled energy-harvesting devices, allowing to use them not only for anti-infective protection but also to supply sensors or active antibacterial/viral devices.

Research of Binary and Ternary Composites Based on Selected Aliphatic or Aliphatic-Aromatic Polymers, 5CB or SWCN Toward Biodegradable Electrodes.

The main goal of this paper was to study the optical, electrical, and thermal properties of hybrid composites based on biodegradable polymers (L,D-poly(lactic acid), polycaprolactone or Ecoflex®), single walled carbon nanotubes (SWCN), and 4'-pentyl-4-biphenylcarbonitrile (5CB). The biodegradable polymers' binary and ternary compositions were analyzed in detail by ultraviolet and visible (UV-Vis) spectroscopy taking into consideration their chemical structure and interactions with 5CB and SWCN. Differential scanning calorimetry (DSC) studies of the created hybrid layers showed thermal stability and changes in glass transition temperature and melting point in comparison to neat polymers, depending on the chemical structure of the polymer used and the type of composition. Morphology of the created layers were investigated by atomic force and polarizing microscopy. The static contact angle measurements of a water drop showed that all of the neat polymer layers were hydrophobic with angle values ranging from 108° to 115°. In addition, in the case of the Ecoflex layers, both with and without additives, a rapid sorption of the deposited water drop was observed. Finally, a simple device with poly(ethylene terephthalate) (PET)/indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly [[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl ]] (PTB7) : [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM)/Ag/biodegradable polymer:SWCN architecture was constructed and tested using an infrared (IR) thermographic camera to investigate the surface defects on the created hybrid layers. Increasing the SWCN admixture from 0.01 to 0.5% significantly improved the conductivity only in the case of L,D-poly(lactic acid):SWCN (10:0.5), for which above 5 V, a current with a resistance of 3030.7 Ω could be measured. In order to use the created layers as flexible electrodes, the first experiments were carried out with an admixture of SWCN and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) as conductive compounds.

Biodistribution, Safety and Organ Toxicity of Docetaxel-Loaded in HER-2 Aptamer Conjugated Ecoflex® Nanoparticles in a Mouse Xenograft Model of Ovarian Cancer.

BACKGROUND: Docetaxel is a notably efficient anticancer drug administered for several types of malignancies including ovarian cancer. However, various side effects caused either by the nonspecific distribution of the active ingredient or by high contents of Tween 80 and ethanol in the currently marketed formulations, could even deprive the patients of the treatment. OBJECTIVES: In the current study, a novel targeted delivery system composed of Ecoflex® polymeric nanoparticles loaded with docetaxel and equipped with HER-2 specific aptamer molecules was evaluated regarding blood and tissue toxicity, and biodistribution. METHOD: The tumor-bearing nude mice, achieved by subcutaneous injection of SKOV-3 cells, were divided into four groups treated with normal saline, Taxotere®, targeted docetaxel nanoparticles, and non-targeted docetaxel nanoparticles. Few patents were alos cied in the article. RESULTS: According to the results of hematologic evaluations, almost all hematologic parameters were in normal range with no significant difference among the four groups. Histopathological studies revealed that treatment with targeted nanoparticles caused a remarkable reduction in mitosis in tumor sections and overall reduced organ toxicity compared with Taxotere®. The only exception was spleen in which more damage was caused by the nanoparticles. The results of the biodistribution study were also in accordance with pathological assessments, with significantly lower drug concentration in non-tumor tissues, except for spleen, when targeted nanoparticles were used compared with Taxotere®. CONCLUSION: These results could evidence the efficiency of the targeted delivery system in concentrating the drug cargo mostly in its site of action leading to the elimination of its adverse effects caused by exposure of other tissues to the cytotoxic agent.

EcoFlex Sponge with Ultrahigh Oil Absorption Capacity.

A paraffin microsphere-templated 3D porous EcoFlex sponge was prepared to selectively absorb oil or chemicals from water. The technology for producing this EcoFlex sponge does not need complicated synthesis processes or instruments, and the materials applied in this work are ecofriendly. Therefore, this sponge can be employed in the environmental field. EcoFlex sponges showed high hydrophobicity (contact angle = 140-143°) and oleophilicity. The developed sponge exhibits a porous three-dimensional framework inside with excellent internal connectivity, which contributes both better absorption capacity and faster absorption rate. For instance, the absorption capacity for chloroform can reach 3400 wt %. The absorption capacity of the sponge was optimized using different size of paraffin microspheres and these sponges exhibit relatively high absorption capacity in a short time (2 min). The volume of sponge expands in some oils and organic solvents: the increased volume capacity for hexane can reach 2200%. This sponge also has great recovery capability and durability; it keeps its original shape and absorption capacity after 15 cycles of oil absorption and compression.

Design of a Soft Composite Finger with Adjustable Joint Stiffness.

This article presents the design of a soft composite finger with tunable joint stiffness. The composite finger, made of two different types of silicone, uses hybrid actuation by combining tendon and pneumatic actuation schemes. Tendons control the finger shape in a prescribed direction to demonstrate discrete bending behavior due to different material moduli, similar to that of a human's finger. The pneumatic actuation changes the stiffness of joints using air chambers. The feasibility of adjustable stiffness joints is proven using both the parallel spring model and experiments that demonstrate the stiffening effect when pressurized. A set of experiments were also conducted on fingers with four different chamber shapes to observe the effect of chamber shape on stiffening and the discrete bending capability of the finger. The stiffness control can tune the structural softness of the finger, which leads to firm grasp during higher acceleration object manipulation.

Direct Patterning of a Carbon Nanotube Thin Layer on a Stretchable Substrate.

Solution-based direct patterning on an elastomer substrate with meniscus-dragging deposition (MDD) enables fabrication of very thin carbon nanotube (CNT) layers in the nanometer scale (80-330 nm). To fabricate the CNT pattern with CNT solution, contact angle, electrical variation, mechanical stress, and surface cracks of elastomer substrate were analyzed to identify the optimal conditions of O2 treatment (treatment for 30 s with RF power of 50 W in O2 atmosphere of 50 sccm) and mixture ratio between Ecoflex and polydimethylsiloxane (PDMS) (Ecoflex:PDMS = 5:1). The type of mask for patterning of the CNT layer was determined through quantitative analysis for sharpness and uniformity of the fabricated CNT pattern. Through these optimization processes, the CNT pattern was produced on the elastomer substrate with selected mask (30 µm thick oriented polypropylene). The thickness of CNT pattern was also controlled to have hundreds nanometer and 500 µm wide rectangular and circular shapes were demonstrated. Furthermore, the change in the current and resistance of the CNT layer according to the applied strain on the elastomer substrate was analyzed. Our results demonstrated the potential of the MDD method for direct CNT patterning with high uniformity and the possibility to fabricate a stretchable sensor.