Material that hears like your ears

Tiny microphones that could see your t-shirt measuring your heart rate.
21 March 2022

Interview with 

Yoel Fink, MIT


a close up of someone with their hand to their ear, trying to listen


Sounds are airborne pressure waves that our ears are well adapted to picking up. But what if your clothes could tune into these tiny waves too? Evelyna Wang spoke with MIT's Yoel Fink who's making fabrics that can listen in like our ears do...

Yoel - In a way fabrics contain the soundtrack of our lives. They are present from very soon after we were born to our last days. However, until now, that soundtrack was not accessible to us. What we set out to do is see if we could create an ear in a fabric.

Evelyna - How did you design a fabric that could pick up on the soundtrack?

Yoel - One thing was that when a sound wave hits a plane or hits a fabric, very small waves are created which aren't that different from the waves that are in water. I'm really referring to those waves that are created in fabrics when we talk to each other. Right now, when you're listening to this podcast, they're very small waves that are generated in the fabrics you're wearing. Now that gets me to another angle, which is the ear. Fibres are an important part of the detection of sound in our ears; both at the front end of hearing, conversion of pressure to vibrations, and also on the back end of hearing, converting those waves into electrical signals. Our work and research focuses on fibres and we then said, 'Wow. Could we take those learnings from the ear and realise that same type of hearing functionality, not now in a 3 dimensional, complex and delicate organ, but actually in a 2 dimensional, flat, flexible and durable, and maybe even machine washable fabric?'

Evelyna - Yeah. This fibre that you designed, can you tell me a little bit of detail about what went into it?

Yoel - In order to detect those waves, we needed to construct a fibre that conformed to those waves, that moved with them; Think about a piece of seaweed in the ocean. We needed a fibre that bent with these very slight waves. We also wanted a fibre that not only moved with the waves, but also reported on them and sent us an electrical signal, and that defined the materials we use to make our fibres. There are two important materials. One is very highly flexible, actually most of the fibre is made out of a rubbery type of material, internal to the fibre is a thin layer of a material that we refer to as a piezoelectric. When that material is bent, it generates an electric signal.

Evelyna - Right. So you have this fibre embedded in your fabric bending and causing electrical signals. How then did you gather that and turn it into a sound?

Yoel - In the end you still need to capture that signal and there are small little micro wires that are running through the fibre that conduct that signal to the edge of the fibre, where it could be picked up. Those are just signals. Turning them into information and useful information requires additional steps.

Evelyna - Right. So how far did you guys get on the processing end of the signal?

Yoel - Our general approach to fabric is framed by a vision that 'fabrics are gonna be the next form of computation'. What we're saying is that the cell phone in your pocket is not gonna look like the object in your pocket for much longer. It's gonna look like fabric. We think about that vision in terms of 4 elements. One is making fibres that have some very special properties and functionality like a microphone, but not only microphone we've made fibre batteries. We've made digital fibres, that store information that could run programs and so on. The second step in that vision is to combine those fibres into a fabric, which becomes a computer. We haven't gotten there, but we're getting closer. Step number three is to implement certain programs to understand the context of those signals. Finally, level four of this vision is to provide services through apps. For example, if you have a hearing aid and you want your fabric to help you to function in a noisy environment. You're gonna have an app for that. And if you're a pregnant woman and you wanna listen to the foetal heartbeat, you're gonna have an app for that. We envision a world where the fabrics are gonna be capable of doing lots of different things for us.


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