converted into cognitive action after their detection in neuroprosthetic devices. Brain

activity can be sensed by sensors or the flexible electronic skin. While playing games,

brain simulators are used for attaining the attention of common people. These simulators

are non-invasive and simple; many companies like Neurosky and Focus are selling these

simulators. Long-term stability and high performance can be achieved by using different

fabrication processes and a variety of materials. Conductive polymers provide lower

impedance as contacted with tissues; thus, a high-quality signal is achieved compared to

metal-based electrodes [42].

9.4.2.2 Implantable Recording Devices

Electrodes can record the neural signal when placed in the brain cortex through a technique

called electrocorticography. The resolution of this method is very high as compared to

other methods. Gamma rhythms of higher frequency can decode the sound, speech, and

motor movements from their stored information. Stretchable electrode grids can detect the

signal more conveniently. These grids can record the signals for many months. The brain

area decides the stretchability and number of inserted electrodes. Nanoelctrodes can in­

crease the electrode area and decrease the impedance for capturing a signal [43]. A neural

device is directly connected with neural tissues to lower the signal-to-noise ratio with better

quality. Microscale devices can provide high performance when integrated with bio­

compatible systems.

9.5 Summary and Perspectives

The tremendous efforts for the development of sensory feedback systems lead the skin-

like electronics interface to the implantable human-machine interface. Bioinspiration has

provided the facilities to merge the artificial electronic system with biological systems and

prosthetics. Implementation of artificial sensory networks to prosthetic hands and human

skin is useful to achieve better human-machine interaction.

At the start of this chapter, it was discussed that artificial sensory networks contain

properties similar to the skin; thus, applicable for prosthetic hands and human skin. Then,

the signal transmission process through conditioning, encoding, and conveying from re­

ceptors to the interface of the neural system has been highlighted. Finally, progress in

electrodes has been demonstrated. Advancement in sensing materials features great pro­

mises towards the high level of devices integration, multifunctionality, and softness of the

interfaces. But there are still challenges for the integration of interfaces with full function­

ality such as achievement of recording of humidity, pressure, and heat simultaneously

through intrinsically stretchable designs due to their high density. In the future, research

will focus on the integration of artificial skin in a self-healing system and biodegradability

for prosthetic hands. In the artificial biosignal interface, an output signal is encoded and

conditioned along with it is accessed and processed in between the brain and artificial skin

sensing system. Easy access of output signal to the nervous system, conversion, amplifi­

cation, digitization, and coding of a signal is an important aspect to be explained.

Ring oscillators are the best tools for the digitization and coding of signals [44].

However, the integration of small-scale devices is still under discussion. Flexible

transistors are larger compared to silicon-based transistors. Their integration is still

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