From smart skins to human-machine interfaces, soft conductive materials have immense potential in wearable applications because of their conformity to the human skin. These materials may be adapted for healthcare devices and sensing functionalities, as well as for rehabilitation purposes like surface functional electrical stimulation (sFES), the process of inducing contractions in paralyzed muscles with electric currents. However, variabilities in muscle distribution among individuals pose new challenges against the development of wearable and personalized sFES platforms. To account for the intricate differences between muscles on different sites of the body, we developed a novel material to actualize stimulation electrodes that are adaptable to be of any shape and size, with self-adhesive properties to ensure conformity to body morphology and guarantee stimulation signal stability. The bio-based polymer of carboxymethyl cellulose is used for the hydrogel matrix due to its water solubility, along with poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the conductive additive and tannic acid as the adhesive additive. A mild and biocompatible gelation method involving hydrogen bonds is implemented via the addition of phytic acid, forming the printed hydrogel for the bioelectronic interface within minutes. Compared with conventional stimulation electrodes, the printable hydrogel electrodes can induce muscle movement during sFES with better precision and accuracy.
Triboelectric Nanogenerator (TENG) is a novel technology to convert mechanical energy into electricity for energy harvesting and sensing applications. Therefore, developing high performance TENG systems for practical applications is a very important and attractive topic. This study presents an efficient and extra light-weight TENG device using polyimide aerogel as the main electricity generation component. The small size porosity of the selected material will significantly change the effective dielectric thickness as well as the contact area resulting in the improvement of the TENG electrical output. The performance of proposed porous system in comparison with a system with compressed polyimide layer is evaluated to show the advantage of used aerogel. In addition, the electrical outputs of the enhanced device under different mechanical and electrical conditions are studied. Through the material fabrication and implementation, the proposed TENG can be successfully employed to boost the performance of various TENG-based energy harvesters and self-powered sensors.
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