Design of an Autonomous Jumping Microrobot Sarah Bergbreiter and Prof. Kris Pister Berkeley Sensor and Actuator Center University of California, Berkeley

Motivation Make Silicon Move! Mobile Sensor Networks –Monitoring/surveillance –Search and rescue Bi-modal transportation –Walking, Flying

Jumping: Locomotion Mobility –Obstacles are large Efficiency –What time and energy is required to move a microrobot 1 m and what size obstacles can these robots overcome? 50 m 130 mJ 417 min 10 mg 1 cm 5 mJ 1 min 10 mg ** 1.5 mJ 15 sec 11.9 mg Obstacle Size Energy Time Mass Hollar (Walking) Proposed (Jumping) Ant (Walking) A. Lipp, H. Wolf, and F.O. Lehmann., “Walking on inclines: energetics of locomotion in the ant Camponotus," Journal of Experimental Biology 208(4) Feb 2005, S. Hollar, "A Solar-Powered, Milligram Prototype Robot from a Three-Chip Process," in Mechanical Engineering: University of California, Berkeley, 2003.

Jumping: Challenges Kinetic energy for jump derived from work done by motors –High force, large throw motors Short legs require short acceleration times –Use energy storage and quick release

Robot Design Power for motors and control Controller to tell robot what to do Spring for energy storage Higher force, larger displacement motor Landing and resetting for next jump are NOT discussed Power Control 1 mm Motors Energy Storage rubber

Power and Control: Design Power Design –Small mass and area –Few (or no) additional components –Simple integration to motors –Supports multiple jumps Control Design –Small size –Low power –Simple integration –Programmability –Off-the-shelf EM6580, 3.5 mg 2 mm1.8 mm Bellew, Hollar (Transducers 2003), 2.3 mg

Energy Storage: Design Small area and mass High efficiency Store large amounts of energy (10s of J) –Support large deflections (many mm) –Withstand high forces (many mN) Integrate easily with MEMS actuators without complex fabrication MaterialE (Pa)Maximum Strain (%) Tensile Strength (Pa) Energy Density (mJ/mm 3 ) Silicon169x x Silicone750x x Resilin2x x10 6 4

Energy Storage: Fabrication 100  m 500  m Sylgard ®  m 100  m Stored ~ 20 J –Equivalent to 20 cm jump height Around 90% efficient

Actuators: Design Small area and mass Low input power and moderate voltage Reasonable speed Do large amounts of work (10s of J) to store energy for jump –Large displacements (5 mm) –High forces (10 mN) Simple fabrication 1 mm l + - V g t k F

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

Actuators: Inchworm Motors Inchworm actuation accumulates short displacements for long throw May be fabricated in single mask SOI process

250  m Actuators: Higher Forces g i,1 g t,f +V g i,0 g t,0 g t,gap

Prototypes: System level demo 30 V solar cells driving EM6580 microcontroller and small inchworm motor

Prototypes: Motor + Elastomer Low force electrostatic inchworm motor with micro fabricated rubber band assembled into shuttle rubber band

Prototypes: Quick Release Electrostatic clamps designed to hold leg in place for quick release –Normally-closed configuration for portability Shot a surface mount capacitor 1.5 cm along a glass slide Energy released in less than one video frame (66ms)

Conclusions Designed an autonomous jumping microrobot –Using rubber for energy storage –Higher force actuators Fabricated microrobot parts Demonstrated system-level functionality Put it all together to build an autonomous jumping microrobot! =

Acknowledgments DARPA/SDR, NSF/COINS Berkeley Microlab Seth Hollar and Anita Flynn Leo Choi, Stratos Christianakis, Deepa Mahajan Prof. Ron Fearing and Aaron Hoover