Interfacial Roughness Enhanced Gel/Elastomer Interfacial Bonding Enables Robust and Stretchable Triboelectric Nanogenerator for Reliable Energy Harvesting

Abstract

characteristics enable it to be a promising candidate for powering IoTs. [9][10][11][12][13][14][15] In particular, TENG is expected to be a soft and stretchable device which is highly integrated with human body and motion for powering upcoming era of wearable electronics. The structure of TENG consists of a pair of triboelectrification materials with distinct charge affinities and corresponding back electrodes, which exploits the coupling effect of triboelectrification and electrostatic induction. [16,17] Accordingly, the triboelectrification pairs as well as electrodes are all required with good softness and stretchability to fulfill the goal of soft and stretchable TENG. [18][19][20] Gels possess intrinsic good softness, high stretchability, and good conductivity, which are ideal materials for stretchable electrodes, and many researchers had successfully applied gels as electrodes to fabricate transparent and stretchable TENGs. [21][22][23][24][25][26][27][28] However, different deformations are inevitable in designed application scenarios of flexible electronics, which requires robust structure to suffer the deformations and further keep TENG's output performance. [26,29] Unfortunately, due to the weak interfacial bonding between gel electrodes and triboelectrification elastomers, delamination in gel-based TENG's deformation is a notable problem because it will induce TENG's structural failure. [25,26,30] Moreover, this problem troubles all gel-based devices for flexible electronics, which is not limited to TENG devices. [31][32][33] Given this, researchers have put great endeavors to improve the interfacial bonding for obtaining a more reliable gel-based TENG. The well-accepted method was chemical modification of triboelectrification elastomers' surface, which applied benzophenone or plasma with coupling reagent to form chemical conjunction with gel electrodes. [32][33][34][35] The chemical conjunction was tough and the bonding strength can surpass gels' tensile strength. The gel-based devices thus can undergo deformations without delamination. However, this method required more chemical steps, implying a much more complicated way. Some researchers employed adhesive gels or altered the triboelectrification materials for naturally intimate interactions between gel layers and triboelectrification layers to avoid the additional complicated chemical modification. [36,37] Nonetheless, this method was only suitable for certain material pairs, not a general method for obtaining tough bonding Gel-based triboelectric nanogenerator (TENG) has demonstrated promising potentials in stretchable electronics owing to gel electrodes' intrinsic softness, stretchability, and conductivity. However, delamination between gel and elastomer layers in deformations remains a considerable challenge for gel-based TENG, which most often induces structure failure. Herein, gels are regarded as adhesives and further effectively enhances interfacial bonding strength by a rough interface in adhesives' view, which exploits gels' liquid-tosoli...

Highly Flexible, High‐Performance, and Stretchable Piezoelectric Sensor Based on a Hierarchical Droplet‐Shaped Ceramics with Enhanced Damage Tolerance

“…Different levels and types of deformation are inevitable in the operation of stretchable devices, which requires robust interfaces to withstand deformation and maintain a stable performance of any sensor. [ 24 ] The bonding strength between two commercial silicone rubbers (PDMS and Ecoflex) and an optimal mix (a PDMS:Ecoflex mixture at a mass ratio of 1:10, Figure S11, termed “P–E”) to the ferroelectric ceramic was therefore evaluated in detail. Figure a shows the tensile stress–strain curves of the peel tests for these composite structures.…”

“…[ 27 ] Since silicone polymers are chemically inert and hierarchical ceramics have interconnected channels with open porosity, mechanical interlocking is considered to be the key factor in determining the interface strength. [ 24,26a ] In terms of classical adhesion theory, the process of mechanical interlocking proposes that adhesion results from polymer penetration into the troughs and pores of a rough substrate. [ 28 ] In order to achieve interlocking, the polymer must exhibit good wettability and fluidity to spread on the ceramic surface and fully penetrate into the pores.…”

Soft Gel Filler Embedded Elastomer with Surfactant Improved Interface for Dielectric Elastomer Actuators

“…Gels are composed of a 3D framework and swelling liquid, which are stretchable and can be designed with high dielectric constant. − Such properties enable gels as ideal fillers for stretchable dielectric materials because these properties can avoid an annoying stiffness problem in rigid fillers and enhance the ε r of composites synchronously. In the introduction of this work, gels were prepared with high softness and dielectric constant for doping elastomers, as shown in Figure .…”

“…In our previous studies, Carbonate-gels were found to be very adhesive. 26,39 Their interfacial binding with elastomers is strong, while liquids usually have no adhesivity to bind to the elastomer. The high interfacial binding results in a high interfacial interaction and thus accounts for the phenomenon that gel fillers are more effective in enhancing dielectric performances than pure liquid fillers.…”

Highly Stretchable, Conductive, Adhesive, and Self-Powered Ionogel Sensor for Human Motion Detection, Signal Transmission, and Traffic Monitoring

“…For electrodes without adhesion, TENG also requires additional means of adhesion or curing to stabilize the structure, which greatly affects the efficiency of device preparation and use. 28 Therefore, the ideal flexible TENG should use both good elasticity (e.g., hydrogel or organogel) and compressive properties (e.g., conductive polymer composites) and at the same time have good environmental stability, high adhesion, and high conductivity electrodes.…”