Microfabrication procedure of PDMS microbeam array using photolithography for laminin printing and piconewton force transduction on axons

The purpose of this paper is to introduce our design for transducing forces on the order of tens of piconewtons by optically measuring deflection of a microfabricated beam tip as it pulls on an array of flexible structures such as axons in an array of laminin-printed neurons. To achieve this we have designed polymeric beams with spring constants on the order of 10pN/µm. We have fabricated circular microbeams with Sylgard® polydimethylsiloxane (PDMS). The elastic modulus of PDMS was determined experimentally using a microscale and a micrometer at different concentrations of curing agent and base agent and found to be on the order of 100kPa. The designed geometry is a 100×100 tapered microcone array with each beam having a length of 100µm, and a base diameter of 10 µm. A SU-8 negative photoresist is etched using photolithography and used as a mold for PDMS soft lithography. PDMS was injected into the mold and the array peeled from the mold.