Triboelectric nanogenerators as new energy technology and self-powered sensors – Principles, problems and perspectives

Abstract

Triboelectrification is one of the most common effects in our daily life, but it is usually taken as a negative effect with very limited positive applications. Here, we invented a triboelectric nanogenerator (TENG) based on organic materials that is used to convert mechanical energy into electricity. The TENG is based on the conjunction of triboelectrification and electrostatic induction, and it utilizes the most common materials available in our daily life, such as papers, fabrics, PTFE, PDMS, Al, PVC etc. In this short review, we first introduce the four most fundamental modes of TENG, based on which a range of applications have been demonstrated. The area power density reaches 1200 W m(-2), volume density reaches 490 kW m(-3), and an energy conversion efficiency of ∼50-85% has been demonstrated. The TENG can be applied to harvest all kinds of mechanical energy that is available in our daily life, such as human motion, walking, vibration, mechanical triggering, rotation energy, wind, a moving automobile, flowing water, rain drops, tide and ocean waves. Therefore, it is a new paradigm for energy harvesting. Furthermore, TENG can be a sensor that directly converts a mechanical triggering into a self-generated electric signal for detection of motion, vibration, mechanical stimuli, physical touching, and biological movement. After a summary of TENG for micro-scale energy harvesting, mega-scale energy harvesting, and self-powered systems, we will present a set of questions that need to be discussed and explored for applications of the TENG. Lastly, since the energy conversion efficiencies for each mode can be different although the materials are the same, depending on the triggering conditions and design geometry. But one common factor that determines the performance of all the TENGs is the charge density on the two surfaces, the saturation value of which may independent of the triggering configurations of the TENG. Therefore, the triboelectric charge density or the relative charge density in reference to a standard material (such as polytetrafluoroethylene (PTFE)) can be taken as a measuring matrix for characterizing the performance of the material for the TENG.

Significant triboelectric enhancement using interfacial piezoelectric ZnO nanosheet layer

“…Now, the PFM signal is given by (8) where d 33 is the piezoelectric strain coefficient, V ac is the driving voltage, and Q is the quality factor [34]. The obtained piezoelectric coefficient of -41 pmV -1 for sample S1 comprising of pristine ZnO nanosheets layer is comparable to the values reported in the literature for the same type of materials [27] and is higher than that for bulk ZnO [27]. The large d 33 for sample S1 is attributed to nanoscale dimensions of the (0002) oriented ZnO nanosheets [26,35].…”

“…The observed high porosity of phase-inversion membranes is highly beneficial in enhancing the performance of the TENGs owing to the increased effective surface area [1,16] and will be discussed further in the following sections. For the pristine PVDF/ZnO/Al system, the contact force still has a significant effect on the output performance of TENGs which is believed to arise from the elastic nature of the contacting materials, with a larger contact force substantially modifying the effective contact/charging area [21,27,28]. In fact, the slope of increase in the case of device S4 (7.55 V/N) is over twice that of device S3 (3.38 V/N) and nearly 2.5 times that of device S2 (2.98 PVDF) TENGs reported in our previous work [16].…”

Fundamental theories and basic principles of triboelectric effect: A review

“…For small particles with identical diameters, the capacitance between them Fig. 2 The four fundamental modes of TENGs: (a) vertical contact mode, (b) lateral sliding mode, (c) single electrode mode, and (d) free-standing triboelectric layer mode [5,22].…”

“…Ironically, with so many tasks to solve and questions to answer, triboelectric devices and applications [4][5][6][7][8] see a far-reaching success in recent years. For example, some previous studies (e.g., into volcanic dusts) have revealed a close relation between environmental phenomena and triboelectric effect [9,10]; manufacturing and processing also face the influence of triboelectrication [11].…”

Early Development of a Design Methodology for Harvesting Natural Resources in Buildings

“…The system is also capable of withstanding forces generated from adults and reasonably larger forces distributed over a small area. The triboelectric nanogenerators (TENGs) capture static electricity which is created from the separation and contact of two materials with opposite triboelectric polarities (Wang, 2014). Here, the electron transfer between the materials is harvested into a usable form.…”