Triboelectric nanogenerators (TENGs) are capable of high-efficiency mechanical energy harvesting, miniaturization and large scale operation, without requiring a high frequency mechanical input like hydroelectric dams and electromagnetic generators. The mechanical energy sources for existing TENGs include water, wind, vibrations, human motion, and more, allowing for the design of many self-powered devices.1 As nanogenerators are still a new field, there exist many functional, stimuli-responsive dielectric materials that have not yet been explored in TENG design. For instance, the lower frequency, wavelike oscillating motion of a polymer film coated with azobenzene derivatives as part of a liquid crystal network has great potential to design a photoactivated TENG. Through a photomechanical effect, azobenzene chromophores in liquid crystal (LC) elastomers are capable of trans-cis photoisomerization when exposed to UV light, which is reversed when exposed to visible light.2
In this work we focus on synthesizing a material for and fabricating an efficient light-driven TENG, in which the azobenzene molecules are altered to possess lower half-lives for cis-trans relaxation and tuned to respond in longer wavelengths of light. First, we will demonstrate synthesis of a fluorinated azyopridine compound that incorporates a push-pull group for fast thermal relaxation. A liquid crystal network containing hydrogen-bonded azyopyridine that incorporates a push-pull group demonstrates continuous wave-like motion when illuminated using UV light.2 Fluorinated azobenzene derivatives have been shown to be effective in tuning the film’s responsiveness to longer wavelengths of light to avoid degradation of the azobenzene by UV light.3 Finally, we demonstrate the efficacy of this compound in creating a light-driven TENG and compare techniques to increase its electrical output.
 Wang, Z.L., ACS Nano 2013, 7 (11), 9533-9557.
 Yamada, M. et al., Angew. Chem 2008, 120 (27), 5064-5066.
 Beharry, A.A. et al., J. Am. Chem. Soc. 2011, 133 (49), 19684-19687.