Self-healing circuits in gadgets could shrink e-waste pile

Flexible electronics such as folding display screens and wearable sensors are all the rage now, but circuits which are more prone to breaking means a higher rate of failure in such devices, scientists said. The result portends a higher burden on e-waste buildup in landfills.

Studies have shown that these devices are prone to open-circuit failures due to mechanical stress from bending or stretching, electric stress from electrostatic discharge due to human contact, and even corrosion from moisture or sweat.

The devices threaten to add to the growing mountain of e-waste being generated worldwide - 53.6 million tonnes was generated worldwide in 2019.

However, an innovation by scientists at the Indian Institute of Science (IISc) in the form of self-healing circuits, could extend the longevity of these devices and ease pressure on landfills.

“Circuit failure in these devices happens because of various mechanical stresses, such as rolling and bending, with the fatigue causing the ‘interconnectivity’ between circuits to crack. This results in black bands appearing on screens, but the cause of failure is really more varied than just a standard breakage between circuits. In wearable devices, corrosion is another cause of breaks,” explained associate professor Sanjeev Sambandan, of the Department of Instrumentation and Applied Physics at IISc, who is the corresponding author for a paper published recently in the journal Advanced Electronics Materials.

A graphic explaining a new self-healing electronic circuit developed by IISc. The innovation could help give longevity to flexible electronics.

Although manufacturers of wearable devices have attempted to mitigate circuit failures through the use of polymers and other manufacturing methods, IISc said that a rethink in circuit design is needed to ensure the longevity of these products.

IISc’s own contribution, made in concert with the University of Cambridge in the United Kingdom, is described as an add-on to existing manufacturing practices - that is using a pico litre of a special “oil” that is printed over the circuits.

“When a circuit breaks, the open current induces particles in the ‘oil’ to align and form a conductive bridge, thereby completing the circuit and ‘healing’ it,” Prof Sambandan explained.

He said IISc is also seeking to take the technology to satellites produced by the Indian Space Research Organization (Isro).

E-waste challenges

What would be the impact on ongoing e-waste generation and recycling? According to Shobha Raghavan, COO, Saahas Zero Waste (SZW), e-waste has already become a thorny proposition. Covid-19 is said to have resulted in buildup of e-waste quantities.

“While most electronics goods have reached the end of their service lives after years of use, wearable gadgets have already started coming in e-waste bundles,” she said.

As the plastics and glass are not recyclable, they usually end up in landfills for burning. “Glass from gadgets contains chemicals and so there is a toxic discharge during burning. There is a historic buildup of e-waste and gadgets are increasingly finding their way into the informal sector, which is adding to pollution,” she added.

She said, however, that the largest sources of e-waste in the near future will be solar panels and electric car batteries.

The Karnataka State Pollution Control Board acknowledged that e-waste disposal is a challenge.

“This is due to the lack of an organised chain to bring the different players together. We are working to address that problem,” said Srinivasulu, member secretary, KSPCB.