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Electrical stimulation of existing three-dimensional bioprinted tissues to alter tissue activities is typically associated with wired delivery, invasive electrode placement, and potential cell damage, minimizing its efficacy in cardiac modulation. Here, we report an optoelectronically active scaffold based on printed gelatin methacryloyl embedded with micro-solar cells, seeded with cardiomyocytes to form light-stimulable tissues. This enables untethered, noninvasive, and damage-free optoelectronic stimulation–induced modulation of cardiac beating behaviors without needing wires or genetic modifications to the tissue solely with light. Pulsed light stimulation of human cardiomyocytes showed that the optoelectronically active scaffold could increase their beating rates (>40%), maintain high cell viability under light stimulation (>96%), and negligibly affect the electrocardiogram morphology. The seeded scaffolds, termed optoelectronically active tissues, were able to successfully accelerate heart beating in vivo in rats. Our work demonstrates a viable wireless, printable, and optically controllable tissue, suggesting a transformative step in future therapy of electrically active tissues/organs. 

Untethered electrical stimulation or pacing of the heart is of critical importance in addressing the pressing needs of cardiovascular diseases in both clinical therapies and fundamental studies. Among various stimulation methods, light illumination–induced electrical stimulation via photoelectric effect without any genetic modifications to beating cells/tissues or whole heart has profound benefits. However, a critical bottleneck lies in the lack of a suitable material with tissue-like mechanical softness and deformability and sufficient optoelectronic performances toward effective stimulation. Here, we introduce an ultrathin (<500 nm), stretchy, and self-adhesive rubbery bio-optoelectronic stimulator (RBOES) in a bilayer construct of a rubbery semiconducting nanofilm and a transparent, stretchable gold nanomesh conductor. The RBOES could maintain its optoelectronic performance when it was stretched by 20%. The RBOES was validated to effectively accelerate the beating of the human induced pluripotent stem cell–derived cardiomyocytes. Furthermore, acceleration of ex vivo perfused rat hearts by optoelectronic stimulation with the self-adhered RBOES was achieved with repetitive pulsed light illumination. 

Abstract Accurate anatomical matching for patient-specific electromyographic (EMG) mapping is crucial yet technically challenging in various medical disciplines. The fixed electrode construction of multielectrode arrays (MEAs) makes it nearly impossible to match an individual's unique muscle anatomy. This mismatch between the MEAs and target muscles leads to missing relevant muscle activity, highly redundant data, complicated electrode placement optimization, and inaccuracies in classification algorithms. Here, we present customizable and reconfigurable drawn-on-skin (DoS) MEAs as the first demonstration of high-density EMG mapping from in situ-fabricated electrodes with tunable configurations adapted to subject-specific muscle anatomy. The DoS MEAs show uniform electrical properties and can map EMG activity with high fidelity under skin deformation-induced motion, which stems from the unique and robust skin-electrode interface. They can be used to localize innervation zones (IZs), detect motor unit propagation, and capture EMG signals with consistent quality during large muscle movements. Reconfiguring the electrode arrangement of DoS MEAs to match and extend the coverage of the forearm flexors enables localization of the muscle activity and prevents missed information such as IZs. In addition, DoS MEAs customized to the specific anatomy of subjects produce highly informative data, leading to accurate finger gesture detection and prosthetic control compared with conventional technology. 

Abstract The dissimilarity of material composition in existing stretchable electronics and biological organisms is a key bottleneck, still yet to be resolved, toward seamless integration between stretchable electronics and biological species. For instance, human or animal tissues and skins are fully made out of soft polymer species, while existing stretchable electronics are composed of rigid inorganic materials, either purely or partially. Soft stretchable electronics fully made out of polymeric materials with intrinsic softness and stretchability are sought after and therefore proposed to address this technical challenge. Here, rubbery electronics and sensors fully made out of stretchable polymeric materials including all‐polymer rubbery transistors, sensors, and sensory skin, which have similar material composition to biology, are reported. The fabricated all‐polymer rubbery transistors exhibit field‐effect mobility of 1.11 cm²V^‐1s^‐1and retain their transistor performance even under mechanical stretch of 30%. In addition, all‐polymer rubbery strain and temperature sensors are demonstrated with high gauge factor and good temperature sensing capability. Based on these all‐polymer rubbery electronics, an active‐matrix multiplexed sensory skin on a robotic hand is demonstrated to illustrate one of the applications.