TENG and PENG are extensively studied and potential devices to harness abundantly

available mechanical energy in the environment. These can power electronics without an

external power source under continuous mechanical input in integration with capacitors.

Recent advancements in nanotechnology promoted the advancement and miniaturization

of nanogenerators. These devices can be integrated into wearable electronics for energy

generation and sensing applications (Figure 14.1).

TENG works on the dual principles of triboelectric charging and electric induction. When

two dissimilar materials come into contact, static charges will be produced at their interface

that makes one material positively charged and the other one negatively charged based on

their tendency to gain or lose electrons and generates a potential difference between the

materials. When they are separated, electrons flow from negatively charged material to

positively charged material through the external circuit producing electricity. Based on the

position of material in the triboelectric series, it can be used as either positive material or

negative material. Materials that are far away from each other in the series generate

stronger charges when they come to contact. The common working modes of TENG are

metal-on-dielectric and dielectric-on-dielectric pairs. These can be assembled in various

configurations such as (i) contact sliding mode, (ii) linear sliding mode, (iii) single electrode

mode, and (iv) free-standing mode, as shown in Figure 14.2(i) [25].

Many materials such as wool, rabbit fur, hair, mustard seeds, poly(vinylidene fluoride)

(PVDF), Kapton, lead, etc. show triboelectric effect. Singh et al. developed TENG using

mustard seeds as a positive layer and PVDF as a negative layer which delivered an open

circuit voltage of 84 V and power density of 334 mW/m² at a force of 40 N at 25 Hz

frequency [26]. The major advantages of TENG are cost-effectiveness, easy design, large

output power, and high conversion efficiency. It was established that the performance

and application of TENG greatly depend on the material used for fabrication.

The use of nanomaterials in these nanogenerators has been reported extensively for a

wide variety of sensing applications [27]. Recently Hao et al. used a flexible self-rebound

FIGURE 14.1

Metal organic framework ecosystem based on nanogenerators for powering wearable biosensors. Adapted with

permission [ 21], Copyright (2011) Elsevier, [ 22], Copyright (2012) Springer Nature, [ 23]. Copyright (2020)

Elsevier and [ 24], Copyright (2019) Elsevier.

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