MIT researchers develop wearable fibre computer for health monitoring

Unlike on-body monitoring systems known as wearables, which are located at a single point like the chest, wrist, or finger, fabrics and apparel have an advantage of being in contact with large areas of the body close to vital organs. As such, they present a unique opportunity to measure and understand human physiology and health.

The fibre computer contains a series of microdevices, including sensors, a microcontroller, digital memory, Bluetooth modules, optical communications, and a battery, making up all the necessary components of a computer in a single elastic fibre.

The researchers added four fibre computers to a top and a pair of leggings, with the fibres running along each limb. In their experiments, each independently programmable fibre computer operated a machine-learning model that was trained to autonomously recognise exercises performed by the wearer, resulting in an average accuracy of about 70 per cent.

Surprisingly, once the researchers allowed the individual fibre computers to communicate among themselves, their collective accuracy increased to nearly 95 per cent.

“Our bodies broadcast gigabytes of data through the skin every second in the form of heat, sound, biochemicals, electrical potentials, and light, all of which carry information about our activities, emotions, and health. Unfortunately, most — if not all — of it gets absorbed and then lost in the clothes we wear. Wouldn’t it be great if we could teach clothes to capture, analyse, store, and communicate this important information in the form of valuable health and activity insights?,” said Yoel Fink, a professor of materials science and engineering at MIT, a principal investigator in the Research Laboratory of Electronics (RLE) and the Institute for Soldier Nanotechnologies (ISN), and senior author of a paper on the research.

The use of the fibre computer to understand health conditions and help prevent injury will soon undergo a significant real-world test as well. US Army and Navy service members will be conducting a month-long winter research mission to the Arctic, covering 1,000 kilometres in average temperatures of -40 degrees Fahrenheit. Dozens of base layer merino mesh shirts with fibre computers will be providing real-time information on the health and activity of the individuals participating on this mission, called Musk Ox II.

“In the not-too-distant future, fibre computers will allow us to run apps and get valuable health care and safety services from simple everyday apparel. We are excited to see glimpses of this future in the upcoming Arctic mission through our partners in the US Army, Navy, and DARPA. Helping to keep our service members safe in the harshest environments is an honour and privilege,” Fink said.

He is joined on the paper by co-lead authors Nikhil Gupta, an MIT materials science and engineering graduate student; Henry Cheung MEng and Syamantak Payra, currently a graduate student at Stanford University; John Joannopoulos, the Francis Wright Professor of Physics at MIT and director of the Institute for Soldier Nanotechnologies; as well as others at MIT, Rhode Island School of Design, and Brown University.

The fibre computer builds on more than a decade of work in the Fibers@MIT lab at the RLE and was supported primarily by ISN. In previous papers, the researchers demonstrated methods for incorporating semiconductor devices, optical diodes, memory units, elastic electrical contacts, and sensors into fibres that could be formed into fabrics and garments.

“But we hit a wall in terms of the complexity of the devices we could incorporate into the fibre because of how we were making it. We had to rethink the whole process. At the same time, we wanted to make it elastic and flexible so it would match the properties of traditional fabrics,” said Gupta.

One of the challenges that researchers surmounted is the geometric mismatch between a cylindrical fibre and a planar chip. Connecting wires to small, conductive areas, known as pads, on the outside of each planar microdevice proved to be difficult and prone to failure because complex microdevices have many pads, making it increasingly difficult to find room to attach each wire reliably.

In this new design, the researchers map the 2D pad alignment of each microdevice to a 3D layout using a flexible circuit board called an interposer, which they wrapped into a cylinder. They call this the ‘maki’ design. Then, they attach four separate wires to the sides of the ‘maki’ roll and connected all the components together.

“This advance was crucial for us in terms of being able to incorporate higher functionality computing elements, like the microcontroller and Bluetooth sensor, into the fibre,” said Gupta.

This versatile folding technique could be used with a variety of microelectronic devices, enabling them to incorporate additional functionality. In addition, the researchers fabricated the new fibre computer using a type of thermoplastic elastomer that is several times more flexible than the thermoplastics they used previously. This material enabled them to form a machine-washable, elastic fibre that can stretch more than 60 per cent without failure, as per the research.

They fabricate the fibre computer using a thermal draw process that the Fibers@MIT group pioneered in the early 2000s. The process involves creating a macroscopic version of the fibre computer, called a perform that contains each connected microdevice. This preform is hung in a furnace, melted, and pulled down to form a fibre, which also contains embedded lithium-ion batteries so it can power itself.

This research was supported, in part, by the US Army Research Office Institute for Soldier Nanotechnology (ISN), the US Defense Threat Reduction Agency, the US National Science Foundation, the Fannie and John Hertz Foundation Fellowship, the Paul and Daisy Soros Foundation Fellowship for New Americans, the Stanford-Knight Hennessy Scholars Programme, and the Astronaut Scholarship Foundation.

ALCHEMPro News Desk (RR)