A flexible approach to flexible electronics

Physics Today, February 2014 - Back Scatter

www.phyisicstoday.org

Circuits that are thin, lightweight and bendable

hold promise for a wide variety of applications,

particularly artificial skin, implantable sensors,

and other biomedical devices.

Giovanni Salvatore and colleagues

in the Wearable Computing Group

at ETH Zürich, Switzerland, 

have now demonstrated

an extremely versatile technique

for fabricating flexible circuits.

Starting with an ordinary wafer,

the researchers deposit a thin,

sacrificial polymer layer

that can be easily dissolved.

Next they add an insoluble thin film

that will serve as the ultimate substrate

for the final deposition step 

-the electronic circuitry.

Dissolving the bottom polymer film

frees the circuit-topped insoluble film,

at which point it can be transferred

to its intended destination.

The photo that can be find

on page 68 of the printed edition

highlights one appeal of the technique:

extreme flexibility and conformability.

These film transistors lie on a 1-µm film

[1 µm: is one micrometer,  

a millionth of a meter, 0.000001 m or 10ˆ(-6) m]

of the biocompatible polymer parylene

that's been draped across human hairs

about 100 µm in diameter.

Despite the film's strong curvature,

the transistor behavior is unaffected.

Furthermore, the choice of film materials

allows for significant customization.

The insoluble film could be elastic or prestrained

(see Physics Today, May 2008, page 84),

and the circuit electrodes

could be transparent or opaque.