Nanoscale Electromechanical Characterisation of Functional Polymers

Session

Nanoscale Probing of Physical Properties via AFM & SPM

Authors

Professor Sohini Kar-Narayan (1)

Affiliations

1. University of Cambridge

Keywords

scanning probe microscopy; functional polymers; energy harvesting; mechanobiology; nanoscale characterization

Abstract text

Properties of functional polymers at the nanoscale can be significantly different to their bulk properties. The ability to engineer material properties at the nanoscale gives rise to a wide range of applications in fields such as biomedicine and energy harvesting. Our research involves understanding structure-property and functionality relationships in novel polymer-based piezoelectric and triboelectric 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 sensors and energy harvesters using advanced microscale additive manufacturing techniques to create a range of functional devices, including those aimed at biomedical or clinical applications. 

In this talk, I will discuss two specific examples related to functional polymers for cell biology and energy harvesting applications, and the role of scanning probe microscopy (SPM) based techniques in investigating their functional properties at the nanoscale. In the first example, I will describe how biocompatible poly-L-lactic acid (PLLA) nanotubes grown by template wetting can provide a suitably ‘soft’ surface for cell culture [1], with applications in the field of mechanobiology and tissue engineering. Importantly, the effective stiffness of the nanostructured surface is dependent on the crystallinity and aspect ratio of the nanotubes, which can be controlled through appropriate heat treatment during the fabrication process. Various SPM modes are used to characterize these PLLA nanotubes at the nanoscale. For example, PeakForce^TM Quantitative Nanomechanical Mapping (PF-QNM) is used to reveal the mechanical properties and lamellar structure of the polycrystalline polymer nanotubes, while Kelvin Probe Force microscopy (KPFM) is used to reveal surface charge properties, both of which have major implications for the way cells interact with these nanotubes. In the second example, I will discuss materials-driven progress related to triboelectric energy harvesting, with emphasis on the role of polymer crystallinity and surface polarization as investigated by KPFM, in determining the triboelectric energy harvesting properties of polymeric nanowires [2]. Triboelectric energy harvesting technologies constitute one of the simplest ways of transforming vibrational and frictional energy into electrical energy, and a deeper understanding of nanoscale electromechanical properties of triboelectric polymers can give rise to new materials design strategies for highly efficient devices [3].

 

References

[1] “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* ACS Applied Bio Materials 3, 2140 (2020). 

[2] “Unprecedented Dipole Alignment in α-phase Nylon-11 Nanowires for High-Performance Energy Harvesting Applications”, YS Choi, SK Kim, M Smith, F Williams, ME Vickers, JA Elliott, S Kar-Narayan*, Science Advances 6, eaay5065 (2020). 

[3] “Materials-Related Strategies for Highly Efficient Triboelectric Energy Generators” YS Choi, S-W Kim, S Kar-Narayan*, Advanced Energy Materials 11, 2003802 (2021).