Servo - April 2012

BEND IT LIKE ... PAPER

Remember that freaky air-powered boneless robot? Well, the same group that unleashed that thing on the world (George M. Whitesides' lab at Harvard) has started to manufacture some beautiful (and superbly functional) air-powered Origami robotic actuators out of paper and elastic. These "soft pneumatic actuators" are constructed by combining paper with a silicone elastomer called Exoflex in a mold and casting the composite so that they contain internal pneumatic networks. The process is fast, easy, inexpensive, and repeatable. When the pneumatic networks are inflated with an external source of air, the elastomer expands, creating an actuator.

The key to the funky shapes that these actuators can make is to use paper to constrain the ways in which the elastomer can bend. The simplest form of this is to just place a piece of paper along one side of the elastomer such that when it's inflated, it bends the other way. However, there are lots of creative things that you can do with paper. The examples in the top photo show pneumatic actuators made of accordion-folded paper/elastomer composites that have had certain folds glued together to generate specific shapes when they inflate. The second photo shows an extension actuator lifting a one kilogram weight ( 2. 2 pounds) which is over 100 times the weight of the actuator itself.

Without the weight on top, an actuator like this can fully deploy at approximately the speed of sound. The researchers have also tested structures that can contract, twist, and even act as little lanterns by controlling the amount of light emitted by an embedded LED through aluminum panels.

The last graphic illustrates how it's also possible to embed electronics in these actuators, suggesting the possibility of creating an entire robot from little more than paper, silicone, and wiring. You'd need a pressure source too, but it might be possible to use chemical reactions to generate gas from relatively small amounts of liquids that could themselves be stored in flexible containers within the robot.

The advantages of robots constructed with methods like these are numerous: They're simple to make, flexible, expandable, lightweight, and cheap enough that you could make a whole bunch of them if you wanted to. There's a reason that DARPA has a whole program dedicated to soft robots: They can do all kinds of things (and go all kinds of places) that rigid robots just can't, and with actuators like these, nothing will be able to stop them.

GRASP ON QUADROTORS

The GRASP (General Robotics,Automation, Sensing, and Perception) Lab at the University of Pennsylvania is already famous for its quadrotor tricks, including bots that can fly through windows and hula hoops, build structures, and even land on each other. Now, those big bad quadrotors have been shrunk down into much smaller "nano quadrotors," and the GRASP Lab has been playing around with lots of them. One possible advantage of having smaller quadrotors is that you can cram more of them into a given space, allowing you to perform more complex swarm behaviors. These little beauties are eminently tossable, and it sort of looks like you can just chuck them like ninja stars and they'll self-right and stabilize themselves. Up to 20 of these things can fly in formation all at once, and it's very impressive to see them make a series of different 3D shapes.