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New TakkTile Touch Sensor

April 21, 2013

Providing a good sense of touch has been one of the greatest challenges in robotics — especially in hobby robotics, where budgets are limited and environments are chaotic.  There are force-sensitive resistors, but these require fairly large amounts of pressure to produce a reliable signal.  Then there are capacitive touch sensors, but these only sense touches from certain kinds of things (like fingers), don’t provide any pressure reading, and generally go haywire if they get even a little wet.

Enter the new TakkTile touch sensor.  This amazing gadget, developed at the Harvard School of Engineering and Applied Sciences, takes advantage of yet another sensor that cell phones have made tiny, reliable, and cheap: the MEMS barometer.  These little chips are designed for sensing air pressure, and are intended as altimeters (and weather sensors, I suppose) in cell phones.  The Harvard team has found that if you pour rubber into the metal case surrounding the actual sensor, then they no longer notice air pressure, but instead sense pressure applied to the case — and do so just as sensitively as they previously sensed altitude.  They’ve combined this with a bit of circuitry and firmware to make a self-contained touch sensor that speaks to a host controller over the common I2C protocol.

In the demonstration video below, the researchers show how the sensor handles a 25-lb weight and being struck with a hammer just fine, yet remains sensitive enough to clearly detect a 5g weight.  For the metric-impaired, that’s the weight of a few paperclips.

The team is encouraging “community development” by making everything open, from the CAD drawings of the sensor board, to the source code, to instructions on how to pour your own rubber.  That last step is a bit onerous for most of us, though, because air bubbles tend to get trapped between the rubber and the sensor, greatly reducing sensitivity.  To avoid that, you need to use a vacuum chamber to suck the air out.

Fortunately, those of us who lack the time, skill, or vacuum chamber for that procedure can order pre-made sensor boards from TakkTile.  A strip of five ready-to-use sensors costs $149, or about $30/sensor.  That’s not pennies, but for a touch sensor this sensitive, it’s pretty much unheard of until now.

I can already think of some handy applications for these things.  If you put several on the bottom of each foot on a humanoid robot, it would be able to sense how its weight is distributed on the feet, and adjust to maintain its balance.  This could supplement IMU readings (which are already commonly used) to produce much more robust biped standing and walking.

What applications for these new sensors can you think of?  Weigh in with your thoughts below.

[Read more: Gizmag, Harvard press release, TakkTile home page.]


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