Skin-actuated self-powered devices based on triboelectric nanogenerators (TENGs) have recently garnered increasing attention, as they can be used to develop electronic skins for healthcare, robotic intelligence, and human interface devices. TENGs typically require tribonegative materials to enable the top layers to either be in contact with or be insulated from other specific materials, resulting in suboptimal performance under practical conditions. Here, we describe the fabrication of a soft, transparent, flexible, stretchable, and skin-actuated TENG device using nanostructured polydimethylsiloxane with a silver nanowire transparent contact as a power source to activate commercial small electronic devices. The nanostructured TENG exhibited a high open-circuit voltage of ∼128 V upon contact with the human skin. This value was substantially higher than that of a TENG with no nanostructure (∼51.6 V), which was attributed to a higher effective contact area in the former. An ∼266 μW/ cm 2 power density could be achieved with the nanostructured TENG upon finger touch stimulation. The resulting electrical output power was then used to activate small commercial electronic devices such as light-emitting diodes. Additionally, due to its high transparency and signal response, the developed TENG was successfully implemented as a sensory platform to build a 3 × 3 keypad. The TENG devices were affixed to several objects to monitor daily activities and harvest biomechanical energy. Our findings suggest that the skin-stimulated elastomer-based TENG developed herein could open possibilities in the development of wearable sensors and power sources.

The central processes driving biological phenomena are based on the conduction of ions and electrons in biomaterials, implying the possibility of achieving a fully biomaterial‐based electronic skin. However, finding the appropriate biomaterials for electronic skins is still challenging. Here, a photoresponsive, self‐healable, and biomaterial‐based optoelectronic skin (OE‐skin) fabricated with melanin nanoparticles and silk protein is proposed and the electronic properties and their mechanisms in the artificially generated OE‐skin are reported. Not only does silk protein hydrogel provide a transparent and skin‐compatible platform for use as OE‐skin but it also provides the appropriate environment for melanin to demonstrate high electrical conductivity. The OE‐skin can be considered a p‐type semiconducting material showing high conductivity of up to 6 mS cm−1 in addition to a 40% enhancement in the conductivity by green laser and ultraviolet light emitting diode illuminations. Additionally, the OE‐skin autonomously heals itself from multiple cuts, allowing the restoration of its electrical properties. These material properties enable applications for strain‐sensors, humidity sensors, and ultraviolet light sensors, as well as image pixels to convert light‐lettering into electrical signals. The proposed fully biomaterial‐based OE material platform offers a new way for next‐generation electronic skins to achieve a seamless interface with the human body.

Silk protein is being increasingly introduced as a prospective material for biomedical devices. However, a limited locus to intervene in nature-oriented silk protein makes it challenging to implement on-demand functions to silk. Here, we report how polymorphic transitions are related with molecular structures of artificially synthesized silk protein and design principles to construct a green-lithographic and high-performative protein resist. The repetition number and ratio of two major building blocks in synthesized silk protein are essential to determine the size and content of β-sheet crystallites, and radicals resulting from tyrosine cleavages by the 193 nm laser irradiation induce the β-sheet to α-helix transition. Synthesized silk is designed to exclusively comprise homogeneous building blocks and exhibit high crystallization and tyrosine-richness, thus constituting an excellent basis for developing a high-performance deep-UV photoresist. Additionally, our findings can be conjugated to design an electron-beam resist governed by the different irradiation−protein interaction mechanisms. All synthesis and lithography processes are fully water-based, promising green lithography. Using the engineered silk, a nanopatterned planar color filter showing the reduced angle dependence can be obtained. Our study provides insights into the industrial scale production of silk protein with ondemand functions.

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Ultrathin, breathable, and skin‐compatible epidermal electronics are attractive for wearable and implantable healthcare and biomedical applications. However, materializing and integrating all electronic components on ultrathin platforms is still challenging. Here, a charge‐storing electronic tattoo (E‐tattoo) device with ultrathin, breathable, and skin‐compatible properties is reported. Silk protein nanofibers (SNFs) and carbon nanotubes (CNTs) form the top and bottom electrodes that sandwich the intermediate dielectric layer fabricated using poly(vinyl alcohol) nanofibers. The E‐tattoo capacitors on the deformed skin, show excellent mechanical and electrical stability, and 60 µm‐thick capacitors exhibit frequency‐dependent capacitances (up to 350 pF at 5 kHz) and capability for memory operation. Mechanical bending induces capacitance change, which increases as the bending radius is decreased, indicating mechanical sensing capability of the E‐tattoo. SNF/CNT‐based triboelectric nanogenerator E‐tattoos can be connected to the capacitor E‐tattoo, and the charges generated by multiple bare‐finger touches can be stored in the capacitor (0.23 V for 200 touches). Due to the micro/nanopores in the NF networks, the device exhibits a water vapor transmission rate of 115.04 g m−2 d−1, which is better than that of a commercial band‐aid, as well as ethanol sensing capability. Developed E‐tattoo capacitor can be used for constructing multicomponent integrated ultrathin and epidermal electronics.

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Natural polymer‐based and self‐powered bioelectronic devices are attracting attention owing to an increased interest in human health monitoring and human–machine interfaces. However, obtaining both high efficiency and multifunctionality from a single natural polymer‐based bioelectronics platform is still challenging. Here, molybdenum disulfide (MoS2) nanoparticle‐ and carbon quantum dot (CQDs)‐incorporated deoxyribonucleic acid (DNA) nanocomposites are reported for energy harvesting, motion sensing, and charge storing. With nanomaterial‐based electrodes, the MoS2‐CQD‐DNA nanocomposite exhibits a high triboelectric open‐circuit voltage of 1.6 kV (average) and an output power density of 275 mW cm−2, which is sufficient for turning on hundred light‐emitting diodes and for a highly sensitive motion sensing. Notably, the triboelectric performance can be tuned by external stimuli (light and thermal energy). Thermal and photon energy absorptions by the nanocomposite generate additional charges, resulting in an enhanced triboelectric performance. The MoS2‐CQD‐DNA nanocomposite can also be applied as a capacitor material. Based on the obtained electronic properties, such as capacitances, dielectric constants, work functions, and bandgaps, it is possible that the charges generated by the MoS2‐CQD‐DNA triboelectric nanogenerator can be stored in the MoS2‐CQD‐DNA capacitor. A new way is presented here to expand the application area of self‐powered devices in wearable and implantable electronics.