UC Berkeley

Mechanical energy storage has been studied to enable a self-destructing mote and a jumping microrobot. Just as chemical energy stored in batteries can be used for a wide array of devices, so too can mechanical energy stored in beams. In this work various energy storage elements are designed, fabricated, and tested to create these MEMS systems.

As privacy and data security become increasingly important, new means of keeping that data safe must be developed. A MEMS system has been created to allow a wirelessly enabled mote to destroy itself on command. To achieve this, a cavity is microfabricated, filled with a silicon etchant, and capped with a fracturable membrane. An energy storage device capable applying 100's of milinewtons of force across distances of 10's of microns was designed and fabricated to fracture these membranes. Additionally, an electrostatic latch was developed to electrically trigger the release of the stored energy. The voltage required to keep this latch closed was reduced using a series of lever arms to amplify the electrostatic force.

Two versions of a silicon jumping microrobots were developed as well. The first microrobot had no active force-producing components and used identical energy storage elements as the self-destructing mote project. In the second microrobot design, the energy storage elements were redesigned and optimized to work with an electrostatic inchworm motor. This motor was combined with a rack and pinion system to create a motor system capable of amplifying the force from a standard inchworm motor by a factor of 10. This microrobot was capable of storing 1.0 uJ of mechanical energy and jumping 1 mm when its motors were actuated electrically through tethered inputs. When the energy storage elements were loaded manually and latched using one of the inchworm motors, 4.0 uJ of energy were stored and the microrobot jumped 6.5 mm.

Finally, a design and simulation library was created throughout this work specifically for microrobots. This library, written in MATLAB, can be used to programmatically generate layout files as well as simulation files. While this functionality exists in other software packages, the MATLAB environment enables calculations to be done in-line with the layout. Users can easily add new functions and build upon the existing software. The simulation environment uses a solid body physics simulator to test functionality of microrobots in software before they are fabricated. This helps ensure that new designs work as intended before going through the time intensive and costly process of fabrication in the cleanroom.