Thin, Skin‐Integrated, Stretchable Triboelectric Nanogenerators for Tactile Sensing

Abstract

a trend. [22-27] Currently, self-powered technologies based on piezoelectric materials [28-32] and triboelectric nanogenerator [33-37] are two typical strategies to convert mechanical energy into electricity. Compared to piezoelectric nanogenerator, triboelectric nanogenerator is more suitable for energy harvesting, as it typically can provide much higher output voltage and current. [38-40] However, reports of using triboelectric nanogenerator for flexible sensors are still much less than those of piezoelectric based ones. [41] The typical method of using triboelectric nanogenerator for stress sensing involves difference of electrical signal output with different contact areas. [35,42,43] Therefore, human motion caused contact separations in the wearable triboelectric nanogenerator can result in electricity output and thus tactile sensing. [35] To better meet Recent advances in thin, soft skin-integrated electronics have brought many opportunities in the wearable technics. A simple platform with the functionality of self-powering for epidermal electronics is reported. These electronics can generate electricity from external mechanical stresses that associates with triboelectric effect, and therefore afford excellent performance in tactile sensing and energy harvesting. Combined advances in materials and mechanics of the skin-integrated electronics with high efficiency energy harvesting techniques, triboelectric nanogenerators (TENGs) in an epidermal format is realized for the first time. The dots-distributed electrode pattern allows these electronics exhibiting excellent flexibility and stretchability, distinguishing a broad range of pressures that are relevant to normal body motions. The electricity output of the epidermal device from simple finger tapping modes can achieve >60 V of voltage and >1 µA of current, which is sufficient to light up 15 small light-emitting diodes. Furthermore, the authors also report a 4 × 4 sensor array based on these TENGs, and demonstrate a skin-like electronics for real-time motion monitoring and tactile mapping.

Portable and wearable self-powered systems based on emerging energy harvesting technology

“…In Fig. 3a, Liu et al reported self-powered epidermal electronics with a tactile sensing function 84 . This kind of epidermal electronics can reflect the pressure on the skin, as well as the pressure distribution, through the triboelectric signal, which is of broad potential interest in wearable electronics.…”

Recent progress on flexible nanogenerators toward self‐powered systems

“…[98][99][100][101] Owing to various advantages of TENG, such as a broad range of material selection, simplicity of structure design, cost-effectiveness, and high output, TENG has been intensively explored in the application of flexible power sources and self-powered environmental sensors, which exhibits the great potential for the future development of wearable electronics and the Internet of Things. [102][103][104][105] 3.1 | Operating mechanisms of triboelectricity Figure 5A demonstrates the construction of the first flexible TENG with vertical contact-separation (CS) mode. 88 The basic working principle of TENG is through a conjunction of triboelectrification and electrostatic induction, which is illustrated in Figure 5B in detail.…”

“…Since 2012, the invention of TENG has made full utilization of this effect, converting mechanical energy in the ambient environment into electricity, such as vibrations, wind, water waves, and human motions . Owing to various advantages of TENG, such as a broad range of material selection, simplicity of structure design, cost‐effectiveness, and high output, TENG has been intensively explored in the application of flexible power sources and self‐powered environmental sensors, which exhibits the great potential for the future development of wearable electronics and the Internet of Things …”

A metal-electrode-free, fully integrated, soft triboelectric sensor array for self-powered tactile sensing

“…In particular, tactile sensors capable of transducing physical touch to electrical signals have demonstrated their practical application in human health monitoring, security monitoring, and artificial intelligence [9][10][11][12][13][14][15] based on different transduction mechanisms, including capacitance [16][17][18] , piezoresistivity [19][20][21] , and piezoelectricity 22,23 . Owing to the advantages of high sensitivity, low cost, diverse material selection, and zero power consumption, another type of sensor based on a triboelectric nanogenerator (TENG), with the sensing mechanism of coupling triboelectrification [24][25][26][27] and electrostatic induction 28 , has aroused great interest among researchers [29][30][31][32] . For example, Wang et al 31 reported a self-powered triboelectric sensor matrix composed of polydimethylsiloxane (PDMS) as an electrification layer and patterned Ag electrodes serving as chargesensing components and circuit connections.…”