3D-printed stretchable hybrid piezoelectric-triboelectric nanogenerator for smart tire: Onboard real-time tread wear monitoring system

An affordable yet highly promising device, friction-based triboelectric nanogenerator (TENG) has attracted tremendous attention for harvesting energy from ambient mechanical forces and converting to scalable electrical power. However, the output power from TENG often appears insufficient to run self-powered electronics for the long term. While most research on high-output hybrid TENGs focused on ferroelectric particle-based polymer composites, we propose a coupled 3D-printing and transfer-printing based fabrication method for hybrid barium titanate (BTO)/polydimethylsiloxane (PDMS) bilayer film with adjustable piezoceramic layer thickness. An internally hybridized BTO/PDMS sensor (HTPENG) results in greater charge separation and more efficient impedance matching at the interface of BTO and PDMS elastomer, as opposed to composites. The higher reproducibility and scalable production method can also drive large-scale industrial production. The resulting power density of HTPENG appeared to be 2.20 mW/cm², nearly twice that of non-hybrid PDMS (PTENG). For the application, the hybrid flexible sensor appears to be highly effective for tire tread wear monitoring systems (TWMS). The direct, onboard, self-powered HTPENG sensor can detect tire wear with very high precision and with detection accuracy of ≤ 1 mm. Moreover, HTPENG can additionally function as a force and pressure sensor with a wide detection range (500 N > F > 10 N). Advancing a step closer to smart tires, this proof-of-concept hybrid sensor is, therefore, expected to bring about a sustainable alternative for the manufacture of onboard TWMS devices and possible dashboard integration in the near future.