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Direct observation of shear piezoelectricity in poly-$\small \text{L}$-lactic acid nanowires

Published version
Peer-reviewed

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Abstract

Piezoelectric polymers are capable of interconverting mechanical and electrical energy, and are therefore candidate materials for biomedical applications such as sensors, actuators, and energy harvesters. In particular, nanowires of these materials are attractive as they can be unclamped, flexible and sensitive to small vibrations. Poly-L-lactic acid (PLLA) nanowires have been investigated for their use in biological applications, but their piezoelectric properties have never been fully characterised, even though macroscopic films and fibres have been shown to exhibit shear piezoelectricity. This piezoelectric mode is particularly interesting for in vivo applications where shear forces are especially relevant, and is similar to what has been observed in natural materials such as bone and DNA. Here, using piezo-response force microscopy (PFM), we report the first direct observation of shear piezoelectricity in highly crystalline and oriented PLLA nanowires grown by a novel template-wetting method. Our results are validated using finite-element simulations and numerical analysis, which importantly and more generally allow for accurate interpretation of PFM signals in soft nanostructured materials. Our work opens up the possibility for the development of biocompatible and sustainable piezoelectric nanogenerators and sensors based on polymer nanowires.

Description

Keywords

nanowires, atomic force microscopy, piezoelectric fields, piezoelectric materials, polymers

Journal Title

APL Materials

Conference Name

Journal ISSN

2166-532X
2166-532X

Volume Title

5

Publisher

American Institute of Physics (AIP) Publishing
Sponsorship
European Research Council (639526)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (702868)
S.K.-N., Y.C., and M.S. are grateful for financial support from the European Research Council through an ERC Starting Grant (Grant No. ERC-2014-STG-639526, NANOGEN). M.S. gratefully acknowledges studentship funding from the Cambridge Commonwealth, European and International Trust. Q.J. is grateful for financial support through a Marie Sklodowska Curie Fellowship, No. H2020-MSCAIF-2015-702868. This work was partially funded by the Cambridge Synthetic Biology Strategic Research Initiative through a SynBio Fund.
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