μTugs: Enabling microrobots to deliver macro forces with controllable adhesives

The controllable adhesives used by insects to both carry large loads and move quickly despite their small scale inspires the μTug robot concept. These are small robots that can both move quickly and use controllable adhesion to apply interaction forces many times their body weight. The adhesives enable these autonomous robots to accomplish this feat on a variety of common surfaces without complex infrastructure. The benefits, requirements, and theoretical efficiency of the adhesive in this application are discussed as well as the practical choices of actuator and robot working surface material selection. A robot actuated by piezoelectric bimorphs demonstrates fast walking with a no-load rate of 50 Hz and a loaded rate of 10 Hz. A 12 g shape memory alloy (SMA) actuated robot demonstrates the ability to load more of the adhesive enabling it to tow 6.5 kg on glass (or 500 times its body weight). Continuous rotation actuators (electromagnetic in this case) are demonstrated on another 12 g robot give it nearly unlimited work cycles through gearing. This leads to advantages in towing capacity (up to 22 kg or over 1800 times its body weight), step size, and efficiency. This work shows that using such an adhesive system enables small robots to provide truly human scale interaction forces, despite their size and mass. This will enable future microrobots to not only sense the state of the human environment in which they operate, but apply large enough forces to modify it in response.