This seminar covers our group’s recent work on novel 2D nanomaterials development and mechanical energy harvesting device innovations. In the first half, I will present an ionic layer epitaxy (ILE) technique that uses surfactant monolayers to serve as soft templates guiding the nucleation and growth of 2D nanomaterials in large area beyond the limitation of van der Waals solids. Through this approach, 1 to 2 nm thick, single-crystalline free-standing ZnO nanosheets with sizes up to tens of microns were synthesized at the water-air interface. So far, we have showed successful synthesis results from ZnO, CuO, and CoO, MnO 2 . ILE vastly broadens the range of 2D nanomaterials from layered van der Waals solids to oxide ceramics, opening up opportunities for discoveries of exciting transport, magnetic, photonic, and catalytic properties. In the second half, I will present our developments of wearable and implantable bioelectronic devices that harvest biomechanical energy and convert it into electric stimulations for medical treatments. We developed an electrical stimulation bandage by integrating a flexible nanogenerator and a pair of dressing electrodes on a flexible substrate. Rat studies demonstrated rapid closure of a full-thickness rectangular skin wound within 3 days as compared to 12 days of usual contraction-based healing processes in rodents. From in vitro studies, the accelerated skin wound healing was attributed to the electric field-facilitated fibroblast migration, proliferation and transdifferentiation. In another work, an implanted vagus nerve stimulation system was developed. The device is attached on the surface of stomach and generates electric pulses in responsive to the peristalsis of stomach. The electric signals generated by this device stimulates the vagal afferent fibers to reduce food intake and achieve 38% weight loss compared to the control groups. Both results bring a new concept in electrical therapeutic technology that is battery-free, self-activated and directly responsive to body activities.
Xudong Wang is a professor in the Dept. of Materials Science & Engineering at Univ. of Wisconsin-Madison. He received his PhD degree in Materials Science and Engineering from Georgia Tech in 2005. His current research interests include studying the growth mechanisms and developing assembly tech-niques of oxide nanostructures; developing advanced nanomaterials and nanodevices for mechanical energy harvesting from human activities and ambient environment; and understanding the coupling effect between piezoelectric polarization and semiconductor functionalities. He has won number of prestigious national and international awards, including NSF CAREER Award, DARPA Young Faculty Award, 3M Non-tenured Faculty Award, Ross Coffin Purdy Award from the American Ceramic Society, and Young Innovators Under 35 Award (TR35) from MIT Technology Review.