New flexible semiconductor is easily degradable

A flexible, biodegradable semiconductor which decomposes when it is no longer needed is being developed by leading researchers at Stanford University.

A release from the University cites a report from the United Nations Environment Program which estimates that almost 50 million tonnes of electronic waste will end up in landfill in 2017 alone.

To combat this trend, Stanford engineer Zhenan Bao and her team are designing a new polymer which is able to degrade into harmless organic matter – decomposing only once the material is exposed to a weak acid, such as vinegar.

The chip is a flexible sheet which can bend and shape to fit around almost any structure. Bao explained how difficult it was to develop a polymer which could both conduct electricity and decompose safely. While previous models built by the Stanford team have been flexible, achieving both biodegradability and flexibility proved to be a complicated challenge.

The solution involves tailoring the chemical links between polymer subunits, called reversible imine bonds. The application of a weak acid results in these bonds breaking, causing the polymer to decompose.

The proof-of-concept also uses experimental electrical components made from iron – an environmentally-friendly metal. Additionally, the researchers created the substrate, which carries the electronic circuit and the polymer, from cellulose. Modifying the cellulose fibres allowed for a transparent and flexible substrate, which was still able to break down easily.

‘The thin film substrate allows the electronics to be worn on the skin or even implanted inside the body,’ noted Bao.

The Stanford team hopes that the new semiconductor could provide a potential replacement for the more rigid structures used in wearables and scientific research. For example, Bao suggests the use of flexible patches which contain embedded processing and sensors and can decompose after a number of days to support medical applications. She also argues that environmental field researchers could make use of the chips, without worrying about gathering up the equipment at a later date.