Research

Wearable bioelectronics. Mechanical properties of hydrogels are crucial to emerging devices and machines for wearables, robotics and energy harvesters. Various polymer network architectures and interactions have been explored for achieving specific mechanical characteristics, however, extreme mechanical property tuning of single-composition hydrogel material and deployment in integrated devices remain challenging. We introduce a macromolecule conformational shaping strategy that enables mechanical programming of polymorphic hydrogel fiber based devices. Conformation of the single-composition polyelectrolyte macromolecule is controlled to evolve from coiling to extending states via a pH-dependent antisolvent phase separation process. The resulting structured hydrogel micro fibers reveal extreme mechanical integrity, including modulus spanning four orders of magnitude, brittleness to ultrastretchability, and plasticity to anelasticity and elasticity.[1]

Polymorphic hydrogel fibers of fibers/ribbons, Janus fibers, multilayered fibers, core-shell fibers, helical Janus fibers, Janus springs and beyond, can be fabricated via our hydrogel wet spinning technology, enabling the translation of extraordinary, realistic hydrogel electronic applications, i.e., large strain (1000%) and ultrafast responsive (~30 ms) fiber sensors in a robotic bird, large deformations (6000%) and antifreezing helical electronic conductors, and large strain (700%) capable Janus springs energy harvesters in wearables.

Smart solar/thermal soft robot. Living organisms are capable of sensing and responding to their environment through reflex driven pathways. The grand challenge for mimicking such natural intelligence in miniature robots lies in achieving highly integrated body functionality, actuation, and sensing mechanisms. A somatosensory light-driven robots (SLiRs) based on a smart thin-film composite tightly integrating actuation and multisensing are presented. The SLiR subsumes pyroelectric/piezoelectric responses and piezoresistive strain sensation under a photoactuator transducer, enabling simultaneous yet non-interfering perception of its body temperature and actuation deformation states. A SLiR anthropomorphic hand shows bodily senses arising from concerted mechanoreception, thermoreception, proprioception, and photoreception. Untethered operation with an SLiR centipede is demonstrated, which can execute distinct, localized body functions from directional motility, multisensing, to wireless human and environment interactions. We expect the SLiR with embedded sensory system to find potential in active human–robot interaction, wearable robot, environmental data collection robot, and closed-loop control of actuation and sensing system.[3]

Utilization of ubiquitous low-grade waste heat constitutes a possible avenue towards soft matter actuation and energy recovery opportunities. While most soft materials are not all that smart relying on power input of some kind for continuous response, we conceptualize a self-locked thermo-mechano-thermal feedback loop for autonomous motility and energy generation functions. The low-grade heat usually dismissed as ‘not useful’ is used to fuel a soft thermo-mechano-electrical system (TMES) to perform perpetual and untethered multimodal locomotions. The untethered TMES soft robot showcases deterministic motions (translational oscillation, directional rolling, and clockwise /anticlockwise rotation), rapid transitions and dynamic responses without needing power input, on the contrary extracting power from ambient via pyro/piezoelectric effect.[4]

Solar and thermal management. Ordered nanostructures are engineered to selectively reflect solar energy of wavelength range from 250 to 2500 nm for optical sensing and heat management. For example, a thermal nanophotonic-pyroelectric (TNPh-pyro) scheme consisting of a metamaterial multilayer and pyroelectric material, which performs synergistic waste heat rejection and photothermal heat-to-electricity conversion, is presented. Unlike any other pyroelectric configuration, this conceptual design deviates from the conventional by deliberately employing back-reflecting NIR to enable waste heat reutilization to enhance pyroelectric generation, avoiding excessive solar heat uptake and also retaining high visual transparency of the device. TNPh-pyro film with the reflection peak at 920 nm has combined visual transparency (VIS transmittance ~70%) and waste heat rejection capabilities (NIR transmittance ~35%). Passive solar re flective cooling up to 4.1 °C is demonstrated. Meanwhile, the photothermal pyroelectric performance capitalizing on the back-reflecting effect shows an open circuit voltage and short circuit current enhancement of 152% and 146%, respectively.[2]