Nanostructured Piezoelectric Polymers as Soft Electromechanical Interfaces for Biology

The mechanical and electrical environment of a cell is crucial in determining its function and the subsequent behavior of multicellular systems. Platforms through which cells can directly interface with mechanical and electrical stimuli are therefore of great interest. Piezoelectric materials are attractive in this context because of their ability to interconvert mechanical and electrical energy, and piezoelectric nanomaterials, in particular, are ideal candidates for tools within mechanobiology, given their ability to both detect and apply small forces on a length scale that is compatible with cellular dimensions. Properties of piezoelectric polymers at the nanoscale can be significantly different to their bulk properties. [1] The ability to engineer material properties at the nanoscale can give rise to a wide range of applications of these materials in fields such as biomedicine and energy harvesting. Our research involves understanding structure-property and functionality relationships in novel polymer-based piezoelectric nanostructures, with a focus on the role of phase, crystallinity and morphology on their functionality. At the same time, these nanomaterials can also be integrated into electromechanical devices for biology. For example, we show that poly-l-lactic acid nanotubes, grown using a melt-press template wetting technique, can provide a “soft” piezoelectric interface onto which human dermal fibroblasts readily attach. [2] Interestingly, by controlling the crystallinity of the nanotubes, the level of attachment can be regulated. Through detailed nanoscale characterization of these nanotubes, we show how differences in stiffness, surface potential, and piezoelectric activity of these nanotubes result in differences in cellular behavior. We also demonstrate the use of advanced microscale additive manufacturing techniques to create soft functional interfaces based on piezoelectric polymer nanostructures for both sensing and stimulation of cells, and also to enhance and control piezoelectricity in aerosol-jet printed structures based on collagen [3] for possible applications in tissue engineering.<br/> <br/><b>References</b><br/> <br/>[1] “Piezoelectric polymers: Theory, challenges and opportunities” M Smith & S Kar-Narayan, <i>International Materials Reviews</i> <b>67</b>, 65 (2022)<br/> <br/>[2] “Poly-L-lactic acid nanotubes as soft piezoelectric interfaces for biology: controlling cell attachment via polymer crystallinity” M Smith, T Chalklen, C Lindackers, Y Calahorra, C Howe, A Tamboli, DV Bax, DJ Barrett, RE Cameron, SM Best, S Kar-Narayan, <i>ACS Applied Bio Materials</i> <b>3</b>, 2140 (2020).<br/> <br/>[3] “Optimising aerosol jet printing of collagen inks for enhanced piezoelectricity and controlled surface potential”, M Nair, E Inwald, L Ives, KRM See, S Kar-Narayan, <i>Journal of Physics: Materials</i> <b>6</b>, 034001 (2023)