This is the third installment in what could be billed the "building series."  The first two articles focused on rather involved fabrication techniques for larger robots; this time, I'd like to look at two more-accessible techniques for building miniature robots that I learned about at IROS 2009.  The first technique, by Jessica Rajkowski and advisor Sarah Bergbreiter (et. al.) from University of Maryland, is a relatively new method employing multi-step photolithography via inkjet printed masks to build small polymer robots such as inchworms and grippers that are actuated by shape memory alloys (SMAs).  The second technique examined is a bit more mature.  Called "Smart Composite Microstructures" (SCM) and hailing from UC Berkeley's Biomimetic Millisystems Lab, this technique is used to build inexpensive, resilient, folded composite (cardboard, carbon fiber, fiberglass) prototypes with polymer hinges.  Read on for details and videos.

Following up on last week's article about building robot hands with compliant under-actuated fingers, I'd like to examine a technique to build aesthetic shells for robot heads using a combination of 3D-printed master forms, silicone molds, and quick-setting plastic final products.  The technique examined was used by MIT alum Cory Kidd to build 18 prototypes of the Autom weight-loss coach for his PhD dissertation, a product that is being continuously refined at Cory's new startup, Intuitive Automata.  This technique seems a bit involved; I probably would have just outsourced a full 3D printed ABS version of the head, especially since there were 18 of them.  However, I always find these advanced robot fabrication techniques enlightening.

Building capable robot end effectors, particularly high-complexity hands, can be a daunting challenge.  In this article, we will examine the fabrication of a robot hand with compliant, under-actuated fingers that is rugged enough to bounce back from twisting, end-on and side impacts, falls, collisions, and even severe back-bending.  The specific fabrication process explored is akin to shape deposition manufacturing using materials such as resins (epoxy / Delrin) and urethanes (a "rubbery" substance) of various durometer (hardness).  This particular technique was used to build early hand prototypes for MIT's Nexi (or MDS) robot from the Personal Robotics Group, and further refinements resulted in the Meka Robotics H2 Compliant Hands, as seen on the Simon robot.    Read on for details and pictures -- this should be of interest to robotics hobbyists and professionals alike.