Wearable healthcare systems require skin‐adhering electrodes that allow maximal comfort for patients as well as an electronics system to enable signal processing and transmittance. Textile‐based electronics, known as “e‐textiles,” is a platform technology that allows comfort for patients. Here, two‐layered e‐textile patches are designed by controlled permeation of Ag‐particle/fluoropolymer composite ink into a porous textile. The permeated ink forms a cladding onto the nanofibers in the textile substrate, which is beneficial for mechanical and electrical properties of the e‐textile. The printed e‐textile features conductivity of ≈3200 S cm−1, whereas 1000 cycles of 30% uniaxial stretching causes the resistance to increase only by a factor of ≈5, which is acceptable in many applications. Controlling over the penetration depth enables a two‐layer design of the e‐textile, where the sensing electrodes and the conducting traces are printed in the opposite sides of the substrate. The formation of vertical interconnected access is remarkably simple as an injection from a syringe. With the custom‐developed electronic circuits, a surface electromyography system with wireless data transmission is demonstrated. Furthermore, the dry e‐textile patch collects electroencephalography with comparable signal quality to commercial gel electrodes. It is anticipated that the two‐layered e‐textiles will be effective in healthcare and sports applications.

In a cold night, a clear window that will become opaque while retaining the indoor heat is highly desirable for both privacy and energy efficiency. A thermally responsive material that controls both the transmittance of solar radiance (predominantly in the visible and near-infrared wavelengths) and blackbody radiation (mainly in the mid-infrared) can realize such windows with minimal energy consumption. Here, we report a smart coating made from polyampholyte hydrogel (PAH) that transforms from a transparency state to opacity to visible radiation and strengthens opacity to mid-infrared when lowering the temperature as a result of phase separation between the water-rich and polymer-rich phases. To match a typical temperature fluctuation during the day, we fine-tune the phase transition temperature between 25 and 55 °C by introducing a small amount of relatively hydrophobic monomers (0.1 to 0.5 wt % to PAH). To further demonstrate an actively controlled, highly flexible, and high-contrast smart window, we build in an array of electric heaters made of printed elastomeric composite. The multipixelated window offers rapid switching, ∼70 s per cycle, whereas the device can withstand high strain (up to 80%) during operations.

An ex vivo heart perfusion device preserves the donor heart in a warm beating state during transfer between extraction and implantation surgeries. One of the current challenges includes the use of rigid and noncompliant plastic tubes, which causes injuries to the heart at the junction between the tissue and the tube. The compliant and rapidly strain-stiffening mechanical property that generates a “J-shaped” stress–strain behavior is necessary for producing the Windkessel effect, which ensures continuous flow of blood through the aorta. In this study, we mimic the J-shaped and anisotropic stress–strain behavior of human aorta in synthetic elastomers to replace the problematic noncompliant plastic tube. First, we assess the mechanical properties of human (n = 1) and porcine aorta (n = 14) to quantify the nonlinear and anisotropic behavior under uniaxial tensile stress from five different regions of the aorta. Second, fabric-reinforced elastomer composites were prepared by reinforcing silicone elastomers with embedded fabrics in a trilayer geometry. The knitted structures of the fabric provide strain-stiffening as well as anisotropic mechanical properties of the resulting composite in a deterministic manner. By optimizing the combination between different elastomers and fabrics, the resulting composites matched the J-shaped and anisotropic stress–strain behavior of natural human and porcine aorta. Finally, improved analytical constitutive models based on Gent’s and Mooney–Rivlin’s constitutive model (to describe the elastomer matrix) combined with Holzapfel–Gasser–Ogden’s model (to represent the stiffer fabrics) were developed to describe the J-shaped behavior of the natural aortas and the fabric-reinforced composites. We anticipate that the suggested fabric-reinforced silicone elastomer composite design concept can be used to develop complex soft biomaterials, as well as in emerging engineering fields such as soft robotics and microfluidics, where the Windkessel effect can be useful in regulating the flow of fluids.

Electronic skin (e‐skin) is an important building block to achieve human–machine interfaces, functional prostheses, and health monitoring devices. While high pressure and temperature sensitivity with visible indication are important for e‐skins, such multifunctionality often requires complex fabrication and integration processes, which hinders practical applications. Here, a simple solution is shown to fabricate a bimodal e‐skin sensor array that is capable of changing color as a response to a range of temperatures (26–40 °C) with an ability to sense finger tap (≈20 kPa pressure) as a pressure sensor. The bimodal functionality of thermochromic response and tactile sensing is achieved by judicial material selection of our custom‐developed elastomer composite containing thermochromic dye, which is sandwiched by tough and transparent stretchable electrodes of ion‐containing polyampholyte hydrogels. The e‐skin array is potentially promising for applications in internet‐of‐things and soft robotics.