Column: Going Green
Of the inorganic materials, aluminium, borosilicate
glass and graphene are examples of eco-friendly, non- biological materials used in electronics. As for organic materials, silk is a great option due to its biodegradability, biocompatibility and wide range of potential uses. Resins, gums, saccharides, cellulose, gelatine and peptides are all biodegradable and fast becoming popular for use in applications such as sensors, signal transducers and implantable and digestible electronics. Aluminium is considered a “green metal” and “the best
eco metal” due to its recyclability and incredibly long lifespan, since it can be recycled repeatedly without loss in quality. Each metric tonne of recycled aluminium saves nine tonnes of CO2
emissions and avoids having to source
new raw metal from the ground, an expensive and lengthy process. In contrast, an aluminium container can be processed and returned to the shelf in as little as six weeks. On top of its unparalleled recyclability, aluminium
is lightweight, with incredible strength. Practically, the average density of aluminium is between 2.6 and 2.8g/cm³, yet the tensile strength of pure aluminium is around 90MPa, which can be increased to over 690MPa in some alloys. Strength is important for use in electronics, too, but
resistance to corrosion is arguably a more valuable trait. Pure aluminium has a very high electrical conductivity, whilst alloys have lower conductivity, but rarely as low as that of iron or steel.
Borosilicate, glass and graphene Borosilicate glass is made of the same components as regular glass but in different percentages. Its strength, durability and resistance to temperature change result in less need for replacement and, therefore, less waste. Iron isn’t considered a “green” material but a “yellow”
one, since it’s neither good nor bad for the environment. The main reason for including iron alloys in this list are their recyclable properties. This is especially pertinent for electronics where recycling is crucial to avoid environmental degradation. Compared with other heavy metals, iron is the most environmentally-friendly. Graphene is one of the strongest materials on Earth. It
has several characteristics, including high electron mobility that is 100x faster than silicon, thermal conductivity twice that of diamond, electrical conductivity 13x better than copper, and absorption of only 2.3% of reflected light. Graphene can be used in many electronics applications – from faster transistors and bendable phones, to improved touchscreens and advanced circuitry for computers. Given that it is made from one of the most abundant elements on Earth, it is inherently environmentally-friendly. The real issue comes from how graphene is produced:
if it is made using solvents and chemicals, it loses its “green” status due to the toxicity of its production. But, if
Borosilicate glass is made of the same components as regular glass but in different percentages
Graphene – the promising material
it is made using physical processes, with no related chemical discharge to the surrounding environment, then it lives up to its reputation as a wonder material. As consumer demand continues to grow for more
environmentally-friendly products, and as the line between electronic and organic continues to blur, “green” materials will become even more common in electronics. Whether in the form of wearable tech or ecologically-friendlier products, we will likely see electronic devices and systems that will be better for the environment.
www.electronicsworld.com February 2021 17
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