Soft, Spongy, and Conductive Materials as Highly Sensitive Strain/Pressure Sensors for Human Motion Monitoring

David Wang Auditorium, 3rd floor Dalia Maydan Bldg.
Dr. Zhengtao Zhu

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.