Harvesting Motion via Polymers: From Mechanisms to Electricity

For many centuries people have pondered (notably and dubiously Thales of Miletus)^[1] why some materials become electrically charged when brought into contact with other, dissimilar, materials. We now know that this charging phenomena is governed either by piezoelectricity from deformation, for non-centrosymmetric unit cells, or contact electrification (also known as triboelectricity) from interfacial friction. While piezoelectricity (and ferroelectricity) is well understood, the mechanisms of contact electrification remain a subject of debate in the literature.^[2] This debate on the driving force being electron-, ion-, or material-transfer,^[2-3] coupled to poor measurement techniques leading to conflation of piezoelectric and contact electrification,^[4-5] has limited the design of optimal polymer energy harvesters.<br/><br/>If we can develop improved understandings of how polymers charge from friction, we can design devices that can capture motion to harvest electricity,^[6] drive chemical reactions,^[7] or even enable wound healing.^[8]<br/><br/>To address this lack of understanding, we have studied how polymers generate charge at a contact interface. This has linked the polarity of generated charge directly to polymer structure via cohesive energy density,^[9] and surface topography.^[10] These relatively simple understandings have enabled the production of layer-by-layer ‘laminate’ assemblies from arbitrary polymers.^[11] These laminates, which function purely off contact electrification and interfacial friction, generate internal dipole moments that mimic piezoelectric polymers – enabling exceptionally efficient vibrational energy harvesting. Finally, we demonstrate the use of recycled foamed/expanded polystyrene to fabricate such laminates, capable of harvesting over 12 µA and 200 V from just 16 N of force. Moving forwards, these laminates, as well as piezoelectric polymers,^[12] are being studied tools to drive catalytic reactions ranging from fuel production through to small molecule synthesis.<br/><br/>This talk aims to provide a pathway to design highly efficient electromechanically active surfaces from polymers towards catalysis and sustainable chemistry.<br/><br/>References:<br/>[1] P. Iversen, et al., <i>Journal of Electrostatics</i> <b>2012</b>,<i> 70</i>, 309,<i> </i>10.1016/j.elstat.2012.03.002<br/>[2] D. J. Lacks, et al., <i>Nature Reviews Chemistry</i> <b>2019</b>,<i> 3</i>, 465,<i> </i>10.1038/s41570-019-0115-1<br/>[3] A. Šutka, et al., <i>Advanced Materials Interfaces</i> <b>2023</b>,<i> n/a</i>, 2300323, 10.1002/admi.202300323<br/>[4] R. T. Leon, et al., <i>Nano Energy</i> <b>2023</b>,<i> 110</i>, 108445,<i> </i>10.1016/j.nanoen.2023.108445<br/>[5] A. Šutka, et al., <i>Adv. Mater.</i> <b>2020</b>,<i> 32</i>, 2002979,<i> </i>10.1002/adma.202002979<br/>[6] A. Šutka, et al., <i>ACS Applied Energy Materials</i> <b>2023</b>,<i> </i>10.1021/acsaem.3c01196<br/>[7] J. Zhang, et al., <i>Journal of the American Chemical Society</i> <b>2021</b>,<i> 143</i>, 3019,<i> </i>10.1021/jacs.0c11006<br/>[8] F.-C. Kao, et al., <i>Science and Technology of Advanced Materials</i> <b>2022</b>,<i> 23</i>, 1,<i> </i>10.1080/14686996.2021.2015249<br/>[9] P. C. Sherrell, et al., <i>ACS Applied Materials & Interfaces</i> <b>2021</b>,<i> 13</i>, 44935,<i> </i>10.1021/acsami.1c13100<br/>[10] O. Verners, et al., <i>Nano Energy</i> <b>2022</b>,<i> 104</i>, 107914,<i> </i>10.1016/j.nanoen.2022.107914<br/>[11] A. Linarts, et al., <i>Small</i> <b>2023</b>,<i> 19</i>, 2205563, 10.1002/smll.202205563<br/>[12] N. A. Shepelin, et al., <i>Nature Communications</i> <b>2021</b>,<i> 12</i>, 3171,<i> </i>10.1038/s41467-021-23341-3