From the gadgets to wearables and even the artificial intelligence/virtual reality/augmented reality devices that our lives in the future could be all about, there will come mountains of electronic waste. A United Nations University research estimates that by 2018, the world will be throwing out 50 million tonnes of e-waste—that’s almost a quarter higher than what we junked in 2014. So, naturally, as we stand transfixed by the near-daily unveiling of thrilling tech developments, our attention should also have been on tackling this problem. But what do we do when the popular imagination of electronics remains centred on hard, enduring goods?
For some time now, R&D work on easily degradable electronics has occupied the scientific community’s mindspace. Very recently, researchers led by Zhenan Bao, a professor of chemical engineering and material science at Stanford University, unveiled an organic, semiconducting polymer—consisting of reversible imine bonds and building blocks that disintegrate in mild acids like vinegar—that can be used in transistors and logic circuits. Bao et al published their findings in Proceedings of the National Academy of Sciences and Nature earlier this month. The polymer sits on an ultra-thin (800-nm), biodegradable substrate layer of cellulose with high chemical and thermal stability and holds together a flexible circuit of iron electrodes—Bao and team had earlier developed this circuit whose flexibility is modelled after human skin, making it eminently transposable on human subjects and can be thus used in medical devices, biosensors and prosthetic skin. The circuits that are less 1 micrometre in thickness, are ultra-lightweight (with density nearly 2 g/m2) and have an operating voltage of 4V disintegrate into non-toxic byproducts within 30 days in solutions of a pH value of 4.6.
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is arguably the first decomposable semiconductive polymer invented, but a couple of years back, a team at Tufts University had created tiny, dissolvable electronics by encapsulating a conventional circuit in ultra-thin silicon and silk proteins. Using soluble conductors like magnesium and magnesium oxide, the researchers printed soluble circuits on ultra-thin silicon-silk-protein sheets to create create functional transistors, diodes, wireless power coils, temperature and strain sensors, photodetectors, solar cells, radio oscillators and antennas. The researchers had even implanted a device in mice—it released antibiotics at a programmed time-scale before dissolving away. The problem, however, was ensuring a delayed dissolution and bio-compatibility of the waste that was generated, a problem that the Bao polymer-circuit seems to have solved.