Tong Li, University of Wisconsin—Madison
High-Performance Polyvinylidene Difluoride/Dopamine Core/Shell Piezoelectric Nanofiber and Its Application for Biomedical Sensors
Written by Arun Kumar
Our human body has abundant biomechanical energy from repetitive and rhythmic movements such as vascular pulsation, respiratory fluctuations, or heartbeat. Piezoelectric or triboelectric nanogenerators in the form of wearables/implantable over the human skin/tissue can convert the biomechanical energy into useful information to detect critical bio-physiological pressures. This can in turn provide early diagnosis for pressure-related chronic and acute diseases.
Several ceramic-based piezoelectric materials are useful for mechanical energy conversion, but are not preferred in clinics due to their poor biocompatibility and low structural flexibility. A polymeric material like PVDF could rectify biocompatibility issues. But, PVDF has a very weak piezoelectric effect and low ferroelectric stability. Tong Li and his team have an answer to modify the downsides of PVDF! They describe a single-step electrospinning strategy to fabricate core/shell poly(vinylidene difluoride) (PVDF)/dopamine (DA) nanofibers which exhibit a high β-phase content and self-oriented polarization. This makes PVDF suitable as an electromechanical coupler for sensing and energy harvesting.
Intermolecular interactions such as hydrogen bonds and dipole interactions between PVDF and DA nanofibers induce the high piezoelectric property of the material. The continuous interfacing between DA nanofibers forming as an outer shell layer over PVDF is essential in maintaining a high β-phase nucleation in the nanofiber device and also helps achieve the long-term stable piezoelectricity of PVDF with excellent stability. These PVDF/ DA nanofibers could be used as implantable sensors for in vivo monitoring. In vitro cellular biocompatibility was demonstrated with PC12 cells. In vivo experiments on mice with implants show excellent biocompatibility, high stability, and real-time monitoring of breathing patterns and arterial stiffness. The implanted piezoelectric sensor can accurately capture any miniature variance in diaphragmatic contraction and peripheral arterial walls and could potentially help in early detection of respiratory and cardiovascular disorders.
Tong Li's presentation is available through May 31, 2021.