On-skin devices that show both high performance and imperceptibility are desired for physiological information detection, individual protection, and bioenergy conversion with minimal sensory interference. Herein, versatile electrospun micropyramid arrays (EMPAs) combined with ultrathin, ultralight, gas-permeable structures are developed through a self-assembly technology based on wet heterostructured electrified jets to endow various on-skin devices with both superior performance and imperceptibility. The designable self-assembly allows structural and material optimization of EMPAs for on-skin devices applied in daytime radiative cooling, pressure sensing, and bioenergy harvesting. A temperature drop of ~4 °C is obtained via an EMPA-based radiative cooling fabric under a solar intensity of 1 kW m–2. Moreover, detection of an ultraweak fingertip pulse for health diagnosis during monitoring of natural finger manipulation over a wide frequency range is realized by an EMPA piezocapacitive-triboelectric hybrid sensor, which has high sensitivity (19 kPa−1), ultralow detection limit (0.05 Pa), and ultrafast response (≤0.8 ms). Additionally, EMPA nanogenerators with high triboelectric and piezoelectric outputs achieve reliable biomechanical energy harvesting. The flexible self-assembly of EMPAs exhibits immense potential in superb individual healthcare and excellent human-machine interaction in an interference-free and comfortable manner.

As a biodegradable elastomer, poly(1,8-octanediolco-citrate) (POC) has been widely applied in tissue engineering and implantable electronics. However, the unclear degradation mechanism has posed a great challenge for the better application and development of POC. To reveal the degradation mechanism, here, we present a systematic investigation into in vivo and in vitro degradation behaviors of POC. Initially, critical factors, including chemical structures, hydrophilic and water-absorbency characteristics, and degradation reaction of POC, are investigated. Then, various degradation-induced changes during in vitro degradation of POC-x (POC with different cross-linking densities) are monitored and discussed. The results show that (1) cross-linking densities exponentially drop with degradation time; (2) mass loss and PBSabsorption ratio grow nonlinearly; (3) the morphology on the cross-section changes from flat to rough at a microscopic level; (4) the cubic samples keep swelling until they collapse into fragments from a macro view; and (5) the mechanical properties experience a sharp drop at the beginning of degradation. Finally, the in vivo degradation behaviors of POC-x are investigated, and the results are similar to those in vitro. The comprehensive assessment suggests that the in vitro and in vivo degradation of POC occurs primarily through bulk erosion. Inflammation responses triggered by the degradation of POC-x are comparable to poly(lactic acid), or even less obvious. In addition, the mechanical evaluation of POC in the simulated application environment is first proposed and conducted in this work for a more appropriate application. The degradation mechanism of POC revealed will greatly promote the further development and application of POC-based materials in the biomedical field.

Conductive hydrogels (CHs) are regarded as one of the most promising materials for bioelectronic devices on human‐machine interfaces (HMIs). However, conventional CHs cannot conform well with complex skin surfaces, such as hairy or wrinkled skin, due to pre‐formation and insufficient adhesion; they also usually lack antibacterial abilities and require tissue‐harm and time‐consuming preparation (e.g., heating or ultraviolet irradiation), which limits their practical application on HMIs. Herein, an in situ forming CH is proposed by taking advantage of the PEDOT:PSS‐promoted self‐polymerization of zwitterionic [2‐(methacryloyloxy)ethyl]dimethyl‐(3‐sulfopropyl) (SBMA). The hydrogel is formed spontaneously after injection of the precursor solution onto the desired location without any additional treatments. The as‐prepared hydrogel possesses excellent elasticity (elastic recovery >96%), desirable adhesive strength (≈6.5 kPa), biocompatibility, and intrinsically antibacterial properties. Without apparent heat release (<5 °C) during gelation, the hydrogel can form in situ on skin. Additionally, the obtained hydrogel can establish tight contact with skin, forming highly conformal interfaces on hairy skin surfaces and irregular wounds. Finally, the in situ forming hydrogels are applied as conformal epidermal electrodes to record stable and reliable surface electromyogram signals from hairy skin (with high signal‐to‐noise ratio, SNR ≈ 32 dB) and accelerate diabetic wound healing under electrical stimulation.

Tough and self‐healable substrates can enable stretchable electronics long service life. However, for substrates, it still remains a challenge to achieve both high toughness and autonomous self‐healing ability at room temperature. Herein, a strategy by using the combined effects between quadruple H‐bonding and slidable cross‐links is proposed to solve the above issues in the elastomer. The elastomer exhibits high toughness (77.3 MJ m−3), fracture energy (≈127.2 kJ m−2), and good healing efficiency (91 %) at room temperature. The superior performance is ascribed to the inter and intra crosslinking structures of quadruple H‐bonding and polyrotaxanes in the dual crosslinking system. Strain‐induced crystallization of PEG in polyrotaxanes also contributes to the high fracture energy of the elastomers. Furthermore, based on the dual cross‐linked supramolecular elastomer, a highly stretchable and self‐healable electrode containing liquid metal is also fabricated, retaining resistance stability (0.16–0.26 Ω) even at the strain of 1600 %.

Nanogenerators have received much attention due to their potential applications in mechanical energy harvesting and self-powered sensing. Despite the fast development of nanogenerators, improving their performances via effective strategies still remains a great challenge. Herein, we report a ternary coupling effect of a triboelectric–piezoelectric hybrid nanogenerator based on the nanoporous film of poly­(vinylidene fluoride)/BaTiO3 composite nanofibers prepared by electrospinning. The transfer charge density of the triboelectric–piezoelectric hybrid nanogenerator in the optimal coupling state is 2.12 times that of the sum value of the pristine nanoporous piezoelectric and triboelectric nanogenerators as references, which can reach up to 105.6 μC m–2. Enhanced performances of the hybrid nanogenerator are attributed to the improved synergistic coupling for triple effects of pore dipole, triboelectricity, and piezoelectricity. Furthermore, the wearable hybrid nanogenerator is demonstrated to be able to harvest biomechanical energy from actions in life. Our findings provide an effective method for developing high-performance nanogenerators.

The demand for stretchable electronics with a broader working range is increasing for wide application in wearable sensors and e‐skin. However, stretchable conductors based on soft elastomers always exhibit low working range due to the inhomogeneous breakage of the conductive network when stretched. Here, a highly stretchable and self‐healable conductor is reported by adopting polyrotaxane and disulfide bonds into the binding layer. The binding layer (PR‐SS) builds the bridge between polymer substrates (PU‐SS) and silver nanowires (AgNWs). The incorporation of sliding molecules endows the stretchable conductor with a long sensing range (190%) due to the energy dissipation derived from the sliding nature of polyrotaxanes, which is two times higher than the working range (93%) of conductors based on AP‐SS without polyrotaxanes. Furthermore, the mechanism of sliding effect for the polyrotaxanes in the elastomers is investigated by SEM for morphological change of AgNWs, in situ small‐angle x‐ray scattering, as well as stress relaxation experiments. Finally, human‐body‐related sensing tests and a self‐correction system in fitness are designed and demonstrated.

Ionic conductive soft materials for mimicking human skin are a promising topic since they can be thought of as a possible basis for biomimetic sensing. In pursuit of devices with a long working range and low signal delay, conductive materials with low hysteresis and good stretchability are highly demanded. To overcome the challenges of highly stretchable conductive materials with good resilience, herein a chemical design is proposed where polyrotaxanes act as topological cross-linkers to enhance the stretchability by sliding-induced reduced stress concentration while the compatible ionic liquid is introduced as a dispersant for low hysteresis. The obtained ionogels exhibit versatile properties more than low hysteresis (residual strain = 7%) and good stretchability (550%), and also anti-fatigue, biocompatibility, and good adhesion. The low hysteresis is attributed to lower energy dissipation from the well-dispersed polyrotaxanes by compatible ionic liquids. The mechanism provides a new insight in fabricating highly stretchable and low-hysteresis slide-ring materials. Furthermore, the conductivity of the ionogels and their responses to strains and temperatures are measured. Benefiting from the good conductivity and low hysteresis, the ionogel is applied to develop a wireless communication system to realize rapid human-machine interactions.

Evaluation of the oxygen‐mediated effects of clinical and daily activities demands an on‐skin device that can track multi‐vital regional tissue hemodynamics simultaneously. For example, peripheral arterial disease (PAD) is the third most prevalent cardiovascular disease, but the means of diagnosing and monitoring this disease are limited because the affected area is usually in the non‐pulsatile area away from the heart. Herein, we report on an ultrathin and ultralight multi‐vital near‐infrared optoelectronic biosensor for the diagnosis and rehabilitation monitoring of regional tissue hemodynamics, which is suitable for mounting on the skin for long‐term measurement. The device can simultaneously detect tissue oxygen saturation, heart rate, arterial blood oxygen, and tissue perfusion and shows potential for various hypoxia monitoring applications. Moreover, the tissue hemodynamics detected by this device showed a highly accordance with the ankle‐brachial index and CT angiography obtained by traditional clinical methods. Therefore, our design was able to accurately diagnose and effectively evaluate PAD patients before and after surgery. The on‐skin optoelectronic biosensor shows potential in biological oxygen‐mediated behavior evaluation, injury‐state monitoring, PAD clinical diagnosis optimization, and after surgery care.