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Materials Science in Additive Manufacturing Biodegradable sustainable electronics

counterbalance the negative trends conveyed by the short short in comparison to their synthetic counterparts in
life cycle of electronics. technical and economic aspects.
As discussed in this review paper, biodegradable (ii) The biodegradability of various emerging materials has
metals generally convert into their oxides in aqueous been tested and demonstrated only at the laboratory
solutions, and in some cases, they are non-reactive; scale. It is essential to establish their biodegradability
therefore, they can be recycled back for use in another at the industrial scale and also set up standards for
device, an example is liquid metal [165,166] . Researchers their commercial adoption.
have experimented with recovering polymers back (iii) One major challenge is associated with synthesizing
from the solution or degrading them enzymatically. In semiconducting and conducting biodegradable
a previous study, an electrochromic display fabricated polymers that can find application in electronics and
using PEDOT: PSS electrochromic layer, a gelatin-based biomedical devices. To date, it is still challenging to
electrolyte, and Au electrodes deposited on a cellulose retain the conductivity of biodegradable polymers
diacetate substrate was tested for biodegradability study while ensuring their functionality for the desired time.
in accordance with the international standard ISO 14855. Two possible scenarios for solving the issue are either
It was found that 79% of the device was able to degrade biomimicking the biodegradable natural materials
in 9 weeks by the microorganisms. The remaining for electronics properties or using novel chemistries
20% was cellulose diacetate and small amounts of to expand the library of biodegradable conducting
PEDOT: PSS, glycerol, and gelatin [150] . In another study polymers.
by Kwon et al., [167] Ag composite with polycaprolactone (iv) One of the roadblocks for biodegradable materials is
(Ag-PCL) was used as a degradable electronic ink. The their application, especially in biomedical devices. The
composite was embedded with enzymes to catalyze electroresponsive and tissue engineering materials
the hydrolytic degradation of PCL. This technique was have unknown biodegradation profile in vitro and
useful to separate the electronic components, which in vivo. A lot of questions surrounding scaffold
can be recycled even after months of storage with no degradation and integration of cells or tissues with
observable loss in performance. An all-carbon thin-film decomposing scaffold remain unanswered.
paper-based transistor was designed for controllable 10. Conclusions and outlook
decomposition where efficiency to recapture graphene
and carbon nanotubes was more than 95%. All the Development of biodegradable materials can help solve issues
recycled materials could be reprinted in the form of new of e-waste, a growing problem that alone cannot be solved
transistors with nearly identical performance to the thin by recycling and reusing. This review summarizes the most
film transistors (TFTs) created from new ink [151] . current biodegradable materials currently being researched
Although researchers are working to make electronics for their use electronic devices and health-care solutions. The
more environmentally friendly by making them repairable, materials are comprehensively categorized and discussed
recyclable, or degradable so as to reduce the amount according to their electrical conduction, namely, conductors,
of e-waste, another significant challenge to focus on is semiconductors, and insulators. Both natural and synthetic
incorporating the capability to quickly change a sensor materials have been explored as substrates, electrodes, and
or a component according to the need. This will eliminate active layers in many biodegradable devices. However,
the need to replace the entire device helping to further the field of biodegradable electronics is in its infancy, and
reduce the amount of waste produced and serving as both the current biodegradable devices cannot compete with
ecologically and economically viable options. conventional devices in performance. Hence, there is a
need to push research in the direction of exploring novel
9. Challenges biodegradable materials that have better performance. The
library also needs to expand to piezoelectric, piezoresistive,
Much effort has been put in studying and investigating the and energy materials to fully replace electronic circuitry
degradation of materials. However, the topics surrounding in the future. Most biodegradation studies are limited to
the breakdown of the emerging electronic materials and its materials, and it is paramount to evaluate dissolution rates
effects on their performance are new. There are still many of materials with respect to their electrical performance. It
issues that need to be addressed so that the field can fully is still unknown at what point biodegradable devices start
evolve. to become unreliable. This review provides a comprehensive
(i) One of the main challenges in biodegradable materials knowledge regarding the potential of fabricating green
is their commercialization and acceptance by the electronics that can be partially or fully degraded, thus
industry. The synthesized biodegradable materials fall paving way for sustainable electronics.

Volume 1 Issue 3 (2022) 15 https://doi.org/10.18063/msam.v1i3.15