Take a moment and envision an electromagnet: a simple coiled wire driven by a hefty electrical current gives a fully-programmable magnetic field strength (on, off, and everything between). Electromagnets are ubiquitous, but it turns out that there is a little-known device with similar functionality yet zero static power consumption -- they are called electropermanent magnets, and they've been around and in use since the 1960's! A 2010 PhD thesis by MIT Media Lab's Ara Knaian examines the physics, scaling, trade-offs, and several new actuator designs (eg. stepper motors) using these little-known wonders. Recently, electropermanent magnets facilitated an innovation in "programmable matter," where they were instrumental in creating the world's smallest self-contained modular robots to date (12mm/side). Read on for details about this fascinating technology, along with discussions about existing and possible robotic applications.
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!