Dr. Zhengtao Zhu
Department of Chemistry and Applied Biological Sciences
South Dakota School of Mines and Technology
Rapid, South Dakota, 57701, United States
Wearable systems consisted of conformable and lightweight biomedical/strain sensors, power sources, and wireless modules have broad application potentials in human motion monitoring, medical, human-machine interface, safety, and soft-robotics. Our research in this area focuses on combination of conductive nanofibers/polymers and soft scaffold materials (such as elastomers and hydrogels) to design multi-component and multi-functional composite materials. In this talk, I present our recent work on soft, spongy, and conductive materials as highly sensitive strain/pressure sensors for wearable human motion monitoring. Three-dimensional (3D) conductive sponge is assembled by freeze-drying of shortened electrospun nanofibers of polyacrylonitrile (PAN), polyimide (PI), and carbon. The sponge composed of these electrospun nanofibers is ultralight with hierarchical pores; under compressive strain, the resistance change of the 3D conductive sponge shows high sensitivity and stability over a wide range of compressive strain. Highly flexible and compressible conductive sponge is also prepared by one-step dip coating the commercial melamine sponge (MS) in an aqueous dispersion of poly(3,4-ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS). Due to the interconnected porous structure of MS, the conductive PEDOT:PSS@MS has high compressibility and stable piezoresistive response at the compressive strain up to 80%, as well as good reproducibility over 1000 cycles. Versatile pressure sensors fabricated using these conductive sponges are attached to the different parts of human body; the capabilities of these devices to detect a variety of human motions including speaking, finger bending, elbow bending, and walking are evaluated. Furthermore, prototype tactile sensory array based on these pressure sensors is demonstrated.