Harvesting circuits for triboelectric nanogenerators for wearable applications

Abstract

Internet of Things (IoT) and recently Internet of Nano Things (IoNT) bear the promise of new devices able to communicate and assist our daily lives toward wearable technologies which demand a versatile integration such as in wireless body networks (WBN), sensing, and health monitorization. These must comply with stringent constraints on energy usage. Dimensions and complexity intensify the need for small and maintenance-free power sources. Environment energy harvesting and storage is an important approach to sustain operation for a long time. Triboelectric nanogenerators (TENGs) arise as a strong and promising solution to power the new field of outcoming self-sustainable devices, implantable, and wearable devices. They can transform mechanical energy in different modes, have simple structures, and use vulgar and sustainable materials. This paper makes a review about TENGs technology, construction, materials, operation, and focus on strategies for harvesting circuits. Main challenges like efficiency, reliability, energy storage, and sustainability are discussed.

Keywords: Bioelectronics; Biotechnology; Energy materials; Materials application.

Graphical abstract

Figure 1

Triboelectric nanogerators concept (A and B) Biomechanical motion that can be used as energy sources for triboelectric generators (A) and potential applications (B). Adapted from (Fan et al., 2020, Shi et al., 2016; Pyo et al., 2020; Hwang et al., 2020, Ye et al., 2019; Yi et al., 2015; Niu et al., 2015; Kim et al., 2017, Zhu et al., 2013a). (C) Example of a triboelectric nanogenerator with all the essential components, positive and negative triboelectric layers (triboelectric pair), electrodes and an external load.

Figure 2

TENGs configuration and working modes (A and B) Triboelectric nanogenerator in conductor-to-dielectric (A) and dielectric-to-dielectric (B) configuration, with one dielectric active layer paired with a conductive active layer and with two distinct dielectric active layers, respectively. (C) Four main working principles for triboelectric nanogenerators.

Figure 3

TENGs versus PENGs performance Graphical comparison between several piezoelectric nanogenerators (PENG) based on different materials as cellulose (Pusty and Shirage, 2020), PVDF (Bhavanasi et al., 2016, Dong et al., 2017b; Hwang et al., 2020, Ye et al., 2019; Chen et al., 2017, Gong et al., 2017; Dudem et al., 2018, Rawy et al., 2018; Yu et al., 2016), PET (Kang et al., 2017, Zhou et al., 2018a), or PDMS(Maria Joseph Raj et al., 2019) along with some of the previously cited TENG devices incorporating materials as PVDF (Guan et al., 2021; Feng et al., 2021, Soin et al., 2016), PDMS(Wu et al., 2021; Cho et al., 2019, Liu et al., 2016; Ko et al., 2015, Zhu et al., 2013b; Chun et al., 2016, Niu et al., 2013a; Guo et al., 2016, Wang et al., 2020a), PVC(Feng et al., 2021, Soin et al., 2016), or silicon rubber (Tian et al., 2017). Output performances are presented in terms of power density according to the necessary applied force for device operation. Additionally, the gradual color shift (light to dark blue) is associated to the device open-circuit voltage, showing higher values for TENG devices.

Figure 4

TENGs electrical modeling (A–C) (A) Harvesting system block diagram, (B) electrical model of a TENG, (C) demonstration of the V-Q plot, adapted from (Zi et al., 2015).

Figure 5

Charge pumping systems and impedance matching (A–D) (A and B) Structural illustration of external charge excitation triboelectric nanogenerators accompanied by the schematic of the associated electric circuit, adapted from (Liu et al., 2019; Xu et al., 2018a), (C) Illustration and schematic for circuit connection of a rotary charge pumping triboelectric nanogenerator, adapted from (Alam et al., 2020, Bai et al., 2020), (D) Illustration of the three working regions when a TENG is connected to a resistive load. Adapted from (Cheng, 2019, Li et al., 2015). (E) Switched resonant transformer circuit (Niu et al., 2015).

Figure 6

Passive and active full-wave rectifier circuits (A) Diodes. (B) Diode-tied MOS rectifier. (C) Gate cross-coupled NMOS rectifier. (D) Cross-coupled rectifier. (E) Active full-wave rectifier with two actively switched and two cross-gate-coupled MOSFETs (Ramadass and Chandrakasan, 2010b). (F) A self-start enabled synchronous rectifier with a low-power trigger circuit acting as a switch between the energy storage capacitor Vin and a boost converter Vout (Ramadass and Chandrakasan, 2010a)

Figure 7

Circuits for voltage regulation (A) Basic voltage doubler. (B) Example of a Cockcroft-Walton voltage quadrupler circuit and rectifier, based on passive switched-capacitor principle. (C and D) Resonant switched-inductor converters, (C) series-SSHI, (D) parallel-SSHI.

Figure 8

Voltage Buck-boost strategies (A) Representation of a harvesting system with Buck converter topology (Xi et al., 2017). (B) DC-DC switched-mode converters, (i) Buck, (ii) Boost, and (iii) Buck–boost configurations. (C) Self-management switching circuit proposed by Fengben Xi et al., adapted from (Xi et al., 2017).