usage in elastic photonics and soft energy scavenging component, as well as wearable

and implantable technologies [50]. As a result, wide bandgap materials (with a bandgap

of 2.2 electron volts (eV) or higher) have become a promising alternative for overcoming

silicon’s limitations. Flexible wide bandgap semiconductors for wearable and implantable

electronics have outstanding features, such as chemical inertness, better electrical quali­

ties at elevated temperatures, rapid saturation drifting velocity, and high breakdown

voltages [49]. Moreover, tremendous progress has been made in micro electromechanical

system (MEMS) technology for transferring wide bandgap materials onto polymer sur­

faces and forming functioning sensors within the last several years. These flexible wide

bandgap materials are successfully used in enduring electronics, power harvesters, bio­

degradable wearable, and implantable devices [20]. Zinc oxide (ZnO) is among the most

often explored II-VI molecules in optoelectronics with direct bandgap (3.4 eV) and large

electron-hole binding energy (60 meV). This establishes the suitability of these materials

as LEDs and ultra-violet photodetectors [51]. The direct energy bandgap in ZnO nano­

wires was paired with the significant optical absorption to create photodetectors with

excellent photon efficiency. For the ultraviolet light spectrum, the photodetector based on

ZnO nanowires exhibited better sensitivity and remarkable frequency specificity [52].

Wearable and implantable physiological applications demand benign materials. The ZnO

nanowires were shown to be biocompatible by the Hela cells’ 95% survival after 48 hours

of cultivation with it [21]. III-nitrite is an area of excellence for logical circuits in

biomedical applications because of its nontoxicity and biocompatibility, as well as the

flexibility of its electronics [53]. Graphene’s unique properties, including softness, flex­

ibility, transparency, ease of functionalization, and biocompatibility, make it one of the

most fascinating 2D materials [1,54–56]. Because of its deformability and transparency, it

has been used to create innovative nervous system probes for optogenetics [57] and

“smart” endoscopes for cancer detection [58]. MoS2 has a fine thickness, excellent photo-

absorption, and piezoresistivity; consequently, it might be used in a high-density curved

image sensor array for a soft retinal prosthesis and very thin wearable tactile sensors [59].

GaN’s long-term stability, in addition to its biocompatibility, is a great component for

wearable and implanted devices [60].

FIGURE 12.5

Self-powered system (BISS) of the human body shows the conversion of mechanical energy from the human

body to electrical energy. Adapted with permission [ 47]. Copyright 2019, American Chemical Society.

196

Bioelectronics