Having previously written about various artificial muscle technologies, I'd like to examine the electroactive polymer (EAP) variant in more detail.  I'll briefly discuss how EAPs function, then move on to myriad examples of EAPs used in robotics applications, including: biomimetic robot eyes, childrens' toys, and flapping-wing ornithopters.   I'll also look at electroactive polymer artificial muscles (EPAM) that were invented at SRI International and subsequently spun off to startup Artificial Muscle, Inc.  In my favorite example, a hexapod walker was constructed at SRI whose muscles are used for both structural support in addition to actuation.  Now if they could also function as energy storage devices, they'd be the ultimate biological analog.

There was a paper just released in Science (Materials) about "Giant-Stroke, Superelastic Carbon Nanotube Aerogel Muscles." This is a rare case where I believe the research material far exceeds the buzzword hype!  The new material responds to applied voltages by expanding 220% in a few milliseconds, operating in temperatures as low as liquid-nitrogen and as high as the melting point of iron.  It has the strength and stiffness of steel (by weight) in one direction and yet is as compliant as rubber in the other two.  It has extremely low density due its airy (aerogel) properties, is conductive, and transparent.  This materials innovation has the potential to rejuvenate research on artificial muscles, which has generally been focused on shape memory alloys (i.e. nickle-titanium or Nitinol),  piezoelectrics (such as PZT), or electroactive polymers (EAPs).  Read on for a discussion about these alternative technologies, their drawbacks, and why this new material may be a game-changer!

The Situational Awareness Mast (SAM, also known as a Zipper Mast) from Geosystems Inc. is a telescoping linear actuator that has a unique property -- it's stroke length is an order of magnitude greater than its nominal height!  For example, the SAM8 is a 10 lb device with a stroke length (8ft) that is 24 times it's nominal height (4 inches)!  This can be used to vertically translate a robot's sensor suite for better visibility while still allowing for a low profile.  Read on for information on the different Zipper Mast variants, the patent describing the system, and an exclusive video of a Zipper Mast on an iRobot Packbot!