Vertical Pillars for Biological Force Sensing Class update – August 3rd Sarah Coulthard, Nahid Harjee, Nathan Klejwa, Ronald Kwon

Thick SU-8 Characterization Wanted 350um layer SU-8 5 layers of 70um using SU-8 2035 +/- 9um Reduced bake time Better mechanical rigidity Found exposure of 20 x 6s optimal T-topping (slight) and non-vertical side walls (~3) observed

Dicing After exposure but before develop, dice backside of wafer using wafersaw Minimize UV exposure Cutting ~50% through wafer allowed clean breaks

Release Testing Optimal adhesion layer: 50A Cr, 250A Au SU-8 (5um) adhered to quartz for 35min in 49% HF No stiction observed

First Attempt at Fabrication Fabrication completed, diced and released individually

First Attempt at Fabrication Fabrication completed, diced and released individually THEY WORK!!! 5 devices were successfully completed 20 more ready for release

Calibration and Movie Measured resistance change with displacement Movies: Simulation and actual

Next Steps Calibration Write abstract 3 axis displacement vs. voltage (using probes) 3 axis force vs. voltage (using class cantilevers) Write abstract Add 35um spacer layer and test with worms