The impregnation of active phases over the surface of carbon nanotubes or even over

others such as graphene, polymers, and semiconductors is a well-known methodology

that involves the use of organic/inorganic precursors containing the desired target

(metals, amino acids, proteins, etc.). The dissolved precursors in water (or another

solvent) are then added dropwise or in an excess of the solvent over the material. After

constant stirring, the modified material is dried and then calcined to ensure the max­

imum anchoring or adsorption of the active phase or precursor on the surface. When an

excess of solvent is used to further the active phase impregnation, coverage is usually

deficient and dispersion is not good. When the volume is similar to the pore size

(incipient impregnation), a monolayer of the active phase is dispersed over the surface,

and final properties seem to change drastically. In both impregnation methodologies,

incipient wetness and wetness, the interaction of the active phase with the surface is

only by physical adsorption rather than chemical or covalent interaction. Thereby,

other methodologies such as grafting or covalent anchoring are used to achieve a strong

interaction between the desired target/active phase and the surface (generally given by

the external groups as hydroxyls). On the other hand, grafting is crucial when a

covalent interaction is required or desired. For the typical materials that require this

strategy, a chemical bond is formed, and the energy to break them is larger than

physisorption [26].

2.3 Classification of Bioelectronics Materials According to Their

Application

Bioelectronics materials can also be classified according to their application. This classi­

fication is possibly one of the most logical for the end-user since associating groups or sets

by application is natural for human beings. Classification of bioelectronics materials ac­

cording to their application or interaction with a biological system is a specialized method

to identify those materials with suitable thermal, electrical, and mechanical properties.

Said materials for part of high-performance bioelectronics devices and disposables. For

example, it has been found that conductive polymer coatings and silicon-based semi­

conductors conform to high-tech materials that can be accessed relatively easily for so­

phisticated electrical stimulation. In this section, the bioelectronics materials were

classified according to their application as electronic materials to solve medicine and

biology problems, materials for the use of biological systems in electronics, and materials

to interface electronic devices with living systems.

2.3.1 Electronic Materials to Solve Medicine and Biology Problems

This section focuses on those materials that have been developed and approved by the FDA

as inactive ingredients, such as poloxamer, polyvinylpyrrolidone, povidone, polylactide,

polyethylene glycol, or polyvinyl alcohol, which have been proposed as alternatives to

solve problems in medicine and biology and that are commonly found in medical devices,

electroactive scaffolds, photosensitive materials, and in drug delivery systems.

Several physical factors such as toughness, mechanical properties, thermal resistance,

or electrical stimuli-responsiveness are involved in the modulation of biometrics, so the

next generation of bioelectronics devices is conceived from the versatility of

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Bioelectronics