Mechanically Robust Cellulose-Based Piezoelectric Elastomer Formed by Slidable Polyrotaxane Cross-Linker.

Cellulose has great potential in the field of piezoelectricity owing to its high crystallinity; however, it exhibits low processability and poor mechanical robustness. In this study, to enhance the applicability of cellulose-based piezoelectric materials, a robust cellulose-based piezoelectric elastomer with excellent piezoelectric properties was developed by cross-linking cellulose with polyrotaxane (PR). The effects of cross-linking on the mechanical properties and crystalline structures of the resulting elastomers were investigated. The ferroelectric and piezoelectric properties were evaluated from their polarization hysteresis loops and voltage generation characteristics. eHPC25PR75 exhibited 2.7 times higher toughness (20.4 MJ m-3) than eHPC100 (7.57 MJ m-3). It also shows a power density 4.2 times higher (1.34 µW cm-2) than eHPC100 (0.321 µW cm-2). As a result, eHPC25PR75 demonstrated piezosensitivity to mechanical vibrations in a variety of devices that require mechanical robustness. These results can inform the design and development of high-performance piezoelectric devices.

Self-Healable Conductive Hydrogels with High Stretchability and Ultralow Hysteresis for Soft Electronics.

Stretchable sensors based on conductive hydrogels have attracted considerable attention for wearable electronics. However, their practical applications have been limited by the low sensitivity, high hysteresis, and long response times of the hydrogels. In this study, we developed high-performance poly(vinyl alcohol) (PVA)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) based hydrogels post-treated with NaCl, which showed excellent mechanical properties, fast electrical response, and ultralow hysteresis properties. The hydrogels also demonstrated excellent self-healing properties with electrical and mechanical properties comparable to those of the original hydrogel and more than 150% elongation at break after the self-healing process. The high performance of the optimized hydrogels was attributed to the enhanced intermolecular forces between the PVA matrix and PEDOT:PSS, the favorable conformational change of the PEDOT chains, and an increase in localized charges in the hydrogel networks. The hydrogel sensors were capable of tracking large human motion and subtle muscle action in real time with high sensitivity, a fast response time (0.88 s), and low power consumption (<180 µW). Moreover, the sensor was able to monitor human respiration due to chemical changes in the hydrogel. These highly robust, stretchable, conductive, and self-healing PVA/PEDOT:PSS hydrogels, therefore, show great application potential as wearable sensors for monitoring human activity.