Damage-free dry transfer method using stress engineering for high-performance flexible two- and three-dimensional electronics.

Advanced transfer printing technologies have enabled the fabrication of high-performance flexible and stretchable devices, revolutionizing many research fields including soft electronics, optoelectronics, bioelectronics and energy devices. Despite previous innovations, challenges remain, such as safety concerns due to toxic chemicals, the expensive equipment, film damage during the transfer process and difficulty in high-temperature processing. Thus a new transfer printing process is needed for the commercialization of high-performance soft electronic devices. Here we propose a damage-free dry transfer printing strategy based on stress control of the deposited thin films. First, stress-controlled metal bilayer films are deposited using direct current magnetron sputtering. Subsequently, mechanical bending is applied to facilitate the release of the metal bilayer by increasing the overall stress. Experimental and simulation studies elucidate the stress evolution mechanisms during the processes. By using this method, we successfully transfer metal thin films and high-temperature-treated oxide thin films onto flexible or stretchable substrates, enabling the fabrication of two-dimensional flexible electronic devices and three-dimensional multifunctional devices.

Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics.

Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics are developed. The use of nanomaterials (single wall nanotubes and silver nanoparticles) embedded in the oxide nanomembranes significantly enhances mechanical and thermal sensitivities. These mechanical and thermal sensors are utilized in wheelchair control and hypothermia detection, which are useful for patients with strokes.

Multifunctional wearable devices for diagnosis and therapy of movement disorders.

Wearable systems that monitor muscle activity, store data and deliver feedback therapy are the next frontier in personalized medicine and healthcare. However, technical challenges, such as the fabrication of high-performance, energy-efficient sensors and memory modules that are in intimate mechanical contact with soft tissues, in conjunction with controlled delivery of therapeutic agents, limit the wide-scale adoption of such systems. Here, we describe materials, mechanics and designs for multifunctional, wearable-on-the-skin systems that address these challenges via monolithic integration of nanomembranes fabricated with a top-down approach, nanoparticles assembled by bottom-up methods, and stretchable electronics on a tissue-like polymeric substrate. Representative examples of such systems include physiological sensors, non-volatile memory and drug-release actuators. Quantitative analyses of the electronics, mechanics, heat-transfer and drug-diffusion characteristics validate the operation of individual components, thereby enabling system-level multifunctionalities.