Direct current contact-mode triboelectric nanogenerators via systematic phase shifting

Abstract

The intermittency and discontinuous nature of power generation in Triboelectric Nanogenerators (TENGs) are arguably their most significant drawback, despite the promise demonstrated in low-power electronics. Herein, we introduce a novel technology to overcome this issue, in which, built-in systematic phase shifting of multiple poles is used to design a pseudo direct-current TENG. Unlike previous attempts of constructing near direct-current TENGs that base on the segmentation of electrodes of a sliding mode TENG, this technology introduces a new method that depends on planned excitation of constituent TENG units at different time intervals to obtain the necessary phase shifts, achieved by their structural design that contains an asymmetric spatial arrangement. Therefore, the direct current generation for TENG, which was previously limited to the sliding mode TENG units, are expanded to contact-mode TENGs. The technology allows for continuous and smooth operation of the driven loads and paves the way for a new dawn in energy scavenging from mechanical sources. We use the distance-dependent electric field (DDEF) platform to design the systematic phase shifting technology, which is experimentally demonstrated via a freestanding mode TENG (FSTENG) based design, to power a number of prototype devices. The resultant power output of the TENG indicates a crest factor close to 1.1 at relatively low frequencies, the best reported values for TENGs with contact-mode basic units, to date. This 2 work provides a highly awaited solution to overcome the intermittency and sporadic nature of TENG outputs, thus, promoting the field towards powering next generation autonomous and mobile electronics.

Towards Truly Wearable Systems: Optimizing and Scaling Up Wearable Triboelectric Nanogenerators

“…There have been significant improvements in theoretical modeling and optimization methods supported by the DDEF model, TENG impedance plot, V-Q plots, etc., which can be effectively used to further improve the textile-based TENG performances. Furthermore, recent investigations into TENGs have uncovered underlying reasons behind their inherent drawbacks such as the discontinuous and irregular output generation ( Dharmasena, 2020 ), and several innovative methods have been presented such as the development of DC TENG ( Dharmasena et al., 2020 ; Liu et al., 2019a , 2019b ) to overcome such issues. These prospects would potentially pave the way toward highly efficient energy harvesting textiles with wearable and durable properties comparable to typical garments in the future.…”

Direct Current Triboelectric Nanogenerators

“…To overcome this issue, DC-TENG with phase coupling was proposed where a constant DC output can be obtained. [86,88,93,94] A cylindrical multiphase DC-TENG reported by Wang et al, [88] (Figure 2a) consisting of a rotator with fluorinated ethylene propylene film (FEP, as negative triboelectric material) and a cylindrical stator with separated copper foils (as both the electrodes and the positive triboelectric material). The multiphase DC-TENG is composed of TENGs with three different phases (the initial angle of electrodes is different) and each phase of TENG consists of three groups of Cu foils in parallel (Figure 2b).…”

“…A constant DC signal with low crest factor of 1.08 can be obtained via phase coupling (Figure 2d), and the output instability in traditional TENG is addressed effectively. Dharmasena et al [93] developed a systematic phase shifting DC-TENG with traditional TENG in vertical contact-separation working mode as the basic unit as illustrated in Figure 2e. A polyethylene terephthalate (PET) sheet is covered with low density polyethylene (LDPE) as the vibrating membrane and sandwiched by two PET sheets with In 2 O 3 /Ag/Au conductive coating on the back.…”

“…The phase difference of the current signal of each unit makes the peak current evenly distributed, and the current signal is more stable and uniform after coupling. [93] In short, the key to attain constant DC output through phase coupling is to enable each TENG power generation unit for producing the current signal with phase difference via specific design structure. [86,88,93,94] Ryu et al [86] realized phase shifting of current signal with the segmentation of electrodes.…”

“…[93] In short, the key to attain constant DC output through phase coupling is to enable each TENG power generation unit for producing the current signal with phase difference via specific design structure. [86,88,93,94] Ryu et al [86] realized phase shifting of current signal with the segmentation of electrodes. The DC-TENG consists of a rotator made of polytetrafluoroethylene (PTFE) and mono cast (MC) nylon and a stator made of PTFE with segmented Cu electrodes ( Figure 2i).…”