to convert brittle inorganic materials into flexible systems, maintaining their electronic

mobility and stability. In inorganic systems, flexibility may achieve by reducing the

thickness and elasticity through the design of undulating structures; moreover, flexible

inorganic systems are usually supported or encapsulated in polymeric materials [5]. On

the other hand, organic bioelectronics materials are those based on carbon, generally

conductive polymers or allotropes of carbon such as graphene or carbon nanotubes, these

materials tend to have higher biocompatibility due to their mechanical properties are

compatible with biological tissues; besides, they have greater versatility of manufacturing

than inorganic materials.

In the classification according to the application, bioelectronics materials may be grouped

into three areas; the electronic materials to solve medicine and biology problems, which

include the detection and characterization of biological materials at the cellular and sub­

cellular level, some examples are materials for electroactive scaffolds, photostimulation, or

drug delivery; biological systems used in electronics application, i.e., new electronic com­

ponents from biological systems; and materials to interface electronic devices with living

systems, such as neural interface electrodes, optical implants, and biosensors for monitoring

physiological functions, through the measurement of electrophysiological signals, biophy­

sical signals (temperature, pressure) and signals biochemical (through body fluids) [6].

2.2 Classification of Bioelectronics Materials According to Their

Composition

According to their composition, bioelectronics materials can be classified into organic or

inorganic. Organic bioelectronics materials for technological applications are common

because of their high biocompatibility. For example, semiconductors and conductors in

electronics and microelectronics interact with biological tissues and usually require some

flexibility and moldability, as well as strength and long cycle life. Therefore, a polymer

matrix is the best option in delicate biological systems. On the other hand, inorganic

semiconductors and conductors provide unique mechanical and conduction properties as

supercapacitors used in bioelectronics tissues. Both inorganic and organic materials must

have biocompatibility as well as functionality for their implementation in bioelectronics

applications and subsequently in living tissue. This section shows the characteristics and

the progress in the bioelectronics application of each material.

2.2.1 Inorganic Bioelectronics Materials

Among the existing materials, such based on inorganics represent an emerging and re­

levant area of research for application in bioelectronics. They can be configured to

harmlessly dissolve, resorb or just degrade at nanometric/molecular scale, as temporary

biomedical implants or environmental sensors. These kinds of materials have been pro­

posed to manufacture deformable and flexible devices, with conductivity, semi-

conductivity, or at least with transduction and energy storage [5]. Inorganic bioelectronics

materials preparation is based on micro-fabrication (film deposition, lithography), and

their successful application depends basically on the type of transfer of the inorganic

function from the substrate to the desired target and a stable communication pathway

between the nervous system and electronic devices [7].

Materials and Their Classifications

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