Self-Powered and Flexible Integrated System Made By Dye Sensitized Solar Cell, Micro-Supercapacitor and Hydrogel-Based Stress Sensor

Abstract

During the last years the development of integrated devices made of a sensor and an energy storage element has found many applications in terms of wearable, implantable and integrated electronics.1,2 The limitation of this system is the periodical need to recharge the energy storage element, making it less suitable for long time remote measurements.Herein, we propose a self-powered and flexible system made by an energy harvester, an energy storage element, and a 3D printed stress sensor. (See figure 1)The harvesting of energy is taken over by a dye sensitized solar cell (DSSC). The DSSC have made their way on the market thanks to the simple fabrication, low payback time and the possibility to customize the choice of electrodes and electrolyte.3 The cell counter electrode is made by laser induced graphene (LIG), gaining the advantage of flexibility with respect to the more common FTO-based counter electrode, as well as more cheapness and ease of fabrication.The solar cell supplies a micro supercapacitor, which is also made by laser induced graphene. LIG supercapacitors are particularly suitable for this application thanks to one-step fabrication (laser writing), flexibility, low costs, high porosity, and lightweight.4,5 The electrodes design has been optimized to obtain a charge balancing and exploiting the whole potential window using a gel-based electrolyte.The supercapacitor is also connected to a hydrogel based flexible sensor. The energy storage discharge current is measured at the ends of the sensor. When the hydrogel is stretched or compressed the resistance of the path is changed, causing a variation of the current that can be measured to retrieve the variation of the stress intensity. Figure 1: Scheme of the self-powered system P. Glynne‐Jones and N. M. White, Sensor Review, 21, 91–98 (2001).M. Parrilla and K. De Wael, Adv Funct Mater, 31, 2107042 (2021).T. V Arjunan and T. S. Senthil, Materials Technology, 28, 9–14 (2013).T. D. Le et al., Adv Funct Mater, 32, 2205158 (2022).P. Zaccagnini and A. Lamberti, Appl Phys Lett, 120, 100501 (2022). Figure 1