Starting with SiC compounds, one of the applications in which they have been most

used is the development of devices that present long-lived recording and sensing. These

devices should have a lifetime of decades in situ, in addition to capability to an integrated

stimulant function, being interesting, for example, to the measurement of cardiac activ­

ities, deep brain stimulators, and pacemakers [21,43,44]. Silicon nanomembranes-on-

polymer (Si) [45] and silicon dioxide (SiO2) [46] are being explored for this type of

application. However, Si undergoes a hydrolysis reaction, with the gradual degradation

of Si-nanomembranes, and SiO2 has a limited function, making its application in detec­

tion and stimulation devices difficult [2]. To optimize these long-lived implants, recent

research shows that SiC exhibits superior properties to Si and SiO2, being promising for

this application. For example, Liu et al. [43] prepared SiC films in memristor medium, for

use in neuromorphic systems and artificial nociceptors, important receptors to recognize

harmful stimuli, such as extreme temperatures and mechanical stress. Phan et al. [21]

were the first to develop flexible SiC nanomembrane platforms. The crystalline cubic SiC

nanomembranes were grown on a Si wafer and then physically transferred to a polyimide

substrate. The interesting system showed water impermeability and mechanical flex­

ibility, in addition to not undergoing the hydrolysis process, making it an important

attraction for application as long-lived flexible implants. Also, in this work, the authors

observed that the sensor based on SiC-polyimide can measure small mechanical strains,

due to the significant piezoresistive effect of SiC. With this ability to convert mechanical

strain into an electrical signal, it is possible to observe the potential of SiC as flexible

mechano-physiological sensors to monitor processes such as pulmonary respiration and

cardiac contractions.

SiC compounds have also been studied as radiofrequency wireless communication

applications. The interesting thing about these devices is that besides detecting/mon­

itoring any signal, they are capable of wireless communication. Afroz et al. [47] devel­

oped a continuous glucose sensor that uses radio frequency (RF) signals using SiC. Sensor

detection is based on a change in resonance frequency due to changes in glucose levels,

causing modifications in blood permittivity and conductivity. For in-vitro sensor per­

formance tests, measurements were performed using synthetic body fluid (blood plasma

equivalent) and pig blood. The sensor demonstrated that its response is dose-dependent

at a glucose concentration between 120 to 530 mg/dl, with a shift of 40 and 26 MHz for

simulated blood and pig blood, respectively. This corresponds to a shift of 97 and 67 kHz

per 1 mg/dl change in blood glucose.

Still in this application, another type of wide bandgap compound widely used is GaN,

belonging to the group III-nitride. As GaN has high electron mobility and a high

breakdown field, this material becomes promising for application in RF devices. Chang

et al. [48] reported flexible GaN HEMTs (high electron mobility transistors) with high

thermal dissipation (0.5 W) operating up to 115 GHz without device degradation. This

heat dissipation is an interesting property for RF devices since they need high power for

their operation. Glavin et al. [49] demonstrated a stretchable GaN HEMT device that can

be stretched uniaxially to 0.85% without damage. High cutoff frequencies and maximum

oscillation frequencies greater than 42 and 74 GHz, respectively, at up to 0.43% strain

were achieved, demonstrating a breakthrough in the development of flexible RF devices.

GaN compounds have a high piezoelectric polarization and flexibility, being in­

vestigated for the fabrication of flexible piezotronic strain sensors. Chen et al. [50] de­

veloped a flexible pulse sensor using single-crystalline III-nitride film. The arterial pulse

sensor proved to be more sensitive than traditional sensors when tested in vivo. In another

work, Cheng et al. [51] used GaN p-n junction microwires for a sensitive strain sensor

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Bioelectronics