Flexible Mobile Phones and Wearable Biomedical Devices Advance with Polymer Film Conductivity

A flexible mobile phone or a wearable biomedical device could be the outcome of a polymer film that uses pigment to conduct electricity at higher levels than other conducting plastics.

The film is transparent, so it could be used for phone displays or a wearable bioelectronic sensor that the patient can wear and not notice that it is there. Polymers that conduct electricity exist, but they use a dopant and their manufacture is more complicated, according to the pigmented plastic’s developers. The new polymer is being developed at the Purdue University-based Materials Innovation for Bioelectronics from Intrinsically-stretchable Organics center.

“As opposed to a traditional metal when we think about electrons, here we’re doing a specific chemical reaction [within the film] and when the chemical reacts it’s a charge transfer reaction and that allows the current to flow,” says Purdue University Davidson School of chemical engineering Robert and Sally Weist Associate Professor, Bryan Boudouris. “The pigment groups, they have sites on there [the film] that can undergo electron exchange reactions. So, one of these pigment groups finds another pigment group and they transfer the charge that way [for conductivity].”

Purdue University researchers are working to use a new polymer film, which could make smartphones more bendable, to create tailor-made sensors that could non-invasively monitor glucose levels, heart rate or other biomedical metrics. Credit: Purdue University

Boudouris and his team are using the polymer film to create tailor-made sensors that could non-invasively monitor glucose levels, heart rate or other biomedical metrics. The polymer can interact with aqueous media if need be for medical purposes. As well as the film being able to conduct, it can exchange ions and glucose with the surrounding medium, which may be bodily fluids. The film would have mounted on it, other conducting polymers or flexible semiconductors that would be the electronic components that would make up the rest of the sensing device. Boudouris says this cannot be done as effectively with traditional silicon-based electronics.

As part of the film’s further development, the team will look at the mechanical properties, how it stretches and how flexible it is. Good flexibility would enable it to be worn by someone, monitor their vital signs, but not be noticed. Another part of the further development work is how to power the biomedical device and keep its battery charged.

The team expects the film to be cost-effective because it is made from common chemical precursors. They also expect its manufacturing process will be scalable up to the levels needed for the mass production demands of consumer electronics. Boudouris points out that the film was effective with 500 nanometres thickness and only a few kilograms of the film was needed for, “football fields,” worth of surface area.

Modern smartphones are sandwiches of battery, circuit and display. A handset made largely from the film could see a device that is flexible. The researchers are working with the Purdue Office of Technology Commercialization to patent the innovation and looking for partners to continue developing it.