Ultrasensitive mechanical crack-based sensor inspired by the spider sensory system
we demonstrate that sensors based on nanoscale crack junctions and inspired by the geometry of a spider’s slit organ can attain ultrahigh sensitivity and serve multiple purposes. The sensors are sensitive to strain (with a gauge factor of over 2,000 in the 0–2 percent strain range) and vibration (with the ability to detect amplitudes of approximately 10 nanometers). The device is reversible, reproducible, durable and mechanically flexible, and can thus be easily mounted on human skin as an electronic multipixel array. The ultrahigh mechanosensitivity is attributed to the disconnection–reconnection process undergone by the zip-like nanoscale crack junctions under strain or vibration.

Skin-Like Microfluidic Systems for Capture, Storage and Chemical Analysis of Sweat
Soft, flexible and stretchable microfluidic systems, including embodiments that integrate wireless communication electronics, can intimately and robustly bond to the surface of skin without chemical or mechanical irritation. This integration defines an access point for a small set of sweat glands such that perspiration spontaneously initiates routing of sweat through a microfluidic network and set of reservoirs. Embedded chemical reagents respond in colorimetric fashion to markers such as chloride and hydronium ions, glucose and lactate. Wireless interfaces to digital image capture hardware on a smartphone serve as a means for quantitation.

Water strider inspired at-scale robot that can jump on water
The main goal of the project was to mimic organisms in nature and abstract principles for robotic applications. Generally, the projects is the robot design based on kinematics and dynamics of the mechanisms with a physical intelligence of materials. In contrast to jumping from solid ground, a large driving force and high leg speed do not guarantee a high velocity when jumping on water. Instead, we found that efficient jumping on water is achieved by relatively slow descending speed slow stroke maintaining the driving force at just below the maximum force that would break the water surface (i.e., the maximum surface tension). Jumping mechanisms that suddenly release stored potential energy to produce a large impulsive force therefore cannot be used to recreate water jumping. Our at-scale robotic water-jumping insect (68 mg in weight) employs a biologically-inspired torque reversal catapult mechanism that gradually increases the jumping force as the leg rotates, enabling the robot to attain high momentum without breaking the water surface.

The milliDelta: A high-bandwidth, high-precision, millimeter-scale Delta robot
Delta robots have been widely used in industrial contexts for pick-and-place applications because of their high precision and speed. These qualities are also desirable at the millimeter scale for applications such as vibration cancellation in microsurgery and microassembly or micromanipulation. Developing a millimeter-scale Delta robot that maintains the characteristic input-output behavior and operates with high speed and precision requires overcoming manufacturing and actuation challenges. We present the design, fabrication, and characterization of an adapted Delta robot at the millimeter scale (the “milliDelta”) that leverages printed circuit microelectromechanical system manufacturing techniques and is driven by three independently controlled piezoelectric bending actuators. We validated the design of the milliDelta, where two nonintersecting perpendicular revolute joints were used to replace an ideal universal joint.

Battery-Free, Skin-Like, Wireless Epidermal Senor for Smart Healthcare System
Thin, soft, skin-like sensors capable of precise, continuous measurements of physiological health have broad potential relevance to clinical health care. Use of sensors distributed over a wide area for full-body, spatiotemporal mapping of physiological processes would be a considerable advance for smart healthcare field. Studies with human subjects in clinical sleep laboratories and in adjustable hospital beds demonstrate functionality of the sensors, with potential implications for monitoring of circadian cycles and mitigating risks for pressure-induced skin ulcers. Lastly, our group research materials, device designs, wireless power delivery and communication strategies, and overall system architectures for skin-like, battery-free sensors of temperature and pressure that can be used across the entire body for advanced smart healthcare system.

Development of Flexible Electronics and Multi-Functional Artificial E-Skin using Nanomaterials
Our group introduces a simple, straightforward strategy by exploiting nanocomposite elastomers that combine with highly networked 1D metallic nanowires (NWs) to serve as functional electrodes in skin-mountable electronic devices. The strategy provides a route to enhance important mechanical properties of the ultrathin, conformable electronics against fracture and delamination phenomena, which would be beneficial to the extension of service lifetime. Also, we are conducting theoretical and experimental studies that this type of highly networked nanocomposite elastomers exhibit superior crack resistance, contact adhesion, and normal/shear strength in comparison to the conventional thin film-based counterparts. Our device demonstrations in thermotherapeutic treatments for the joint, surface temperature mapping over the skin, and electrophysiological monitoring from the heart and the muscle illuminate the potential for practical applications with importance in human healthcare.