Page 12 - IJAMD-1-2

International Journal of AI for
Materials and Design
Sustainable electronics using AI/ML

3.3.3. OSs the breakage of chemical bond happens by water;

Various OSs, such as polythiophenes, polypyrrole (PPy), (2) enzymatic degradation through which bond breakage
polyaniline, and poly (phenylene vinylene), have been is induced by enzyme; and (3) oxidative degradation
employed as active materials in numerous electronic through which the oxygen molecules help in breaking
devices to date. Their usage as active material imparts the macromolecules by forming free radicals. The other
improved mechanical conformability and better biological factors affecting the biodegradation rates of the OS
interface, which are crucial for biomedical applications, materials are molecular weight, temperature, pH of the
in addition to bringing added advantages of synthetic medium, surface area of the material, and absence of
tunability and low-cost processing. The conductivity crosslinks. 47
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in these OS materials is offered by the delocalization of 3.4. Dielectric materials
electrons along the π-conjugated backbone. However,
these polymers demonstrate less resistance to degradation Dielectric materials are electrical insulators that exhibit
owing to their strong C-C bond. Nevertheless, one of the polarization when subjected to an electric field. Upon
easy ways to impart biodegradability in these polymers application of an electric field, dipole moments alignment
is to blend them with the nonconducting polymers, takes place, thereby resulting in an internal electric field
eventually making them disintegrable. In this process, that decreases the overall field contained in the dielectric
a dual advantage of having good conductivity as well material. Owing to this property, the applications of
as degradability can be achieved. There have been dielectric materials are widespread in field-effect transistors
several reports demonstrating such blending/grafting of (FETs) and capacitive sensing devices, further leading to
conducting polymers such as PPy with PLA, PPy with poly the realization of medical diagnostics and structural health
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(L-lactide-co-glycolide) (PLGA), and poly (3-thiophene monitoring devices. Typically, they are classified into
methyl acetate) with biodegradable polyester, poly(3,4- organic and inorganic dielectrics. 48
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ethylenedioxythiophene)-poly(styrene sulfonate) with
PLA composite, poly(3-hexylthiophene) (P3HT) with 3.4.1. Inorganic dielectric materials
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PLGA, P3HT blended with PCL, etc., to improve the Magnesium oxide (MgO), silicon dioxide (SiO ), silicon
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composite degradability. Apart from blending/grafting nitride (Si N ), and spin-on-glass are the available potential
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approach, the biodegradability can also be imparted by choices of inorganic dielectric materials capable of being
synthetically modifying the structure of these functional utilized as gate or interlayer dielectrics, passivation
polymers; wherein the desirable electrical and mechanical coatings, and the encapsulation layers of biodegradable
properties can be easily tuned. Such reported strategies electronic devices. 49,50 Among these, SiO and Si N are the
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include polymerization of modified monomers, two most widely used dielectric material in the fabrication
introducing hydrolyzable linkages into conjugated of field effect transistors. Completely biodegradable
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polymer backbone, and co-polymerization of conducting electronic implants consisting of n-channel FETs have
oligomers with biodegradable polymers. 40-44 In general, been developed on a silk substrate using SiO and Si N
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the small OS molecules can be completely biodegradable as a dielectric and an encapsulation layer, respectively.
since they can easily pass through the digestive system. A complete degradation of the fabricated devices has been
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However, the degradation rate of the molecules in various observed in deionized water in <5 min. Notably, MgO
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environments depends on their chemical structure. As has also been used as an inorganic dielectric material in
a rule of thumb, the resistance to biodegradation of a numerous applications. 52
particular molecule increases when the solution contains
strong electron-withdrawing substituents like chlorine. 3.4.2. Organic dielectrics
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Similarly, the presence of extensive branching has been The commonly available organic polymers such
found to reduce the susceptibility to biodegradation. as PLA, PVA, polymethyl methacrylate (PMMA),
Nevertheless, the solution condition and the environment polyvinylpyrrolidone, polypropylene carbonate (PPC),
of the molecule play a critical role in determining its polydimethylsiloxane, and polyurethane (PU) have
biodegradability. been extensively studied as a dielectric material in
The degradation mechanism of organic moieties biodegradable organic electronic devices owing to their
occurs by the cleavage of chemical bonds at the commercial availability and ease of processability. 53-55 The
molecules resulting in non-toxic by-products. In alcohol or acid groups in these polymers can be polarized
general, the degradation process consists of three under an applied electric field, making them a potential
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main mechanisms: (1) hydrolytic degradation where candidate as dielectric materials. Synthetic polymers
Volume 1 Issue 2 (2024) 6 doi: 10.36922/ijamd.3173