Mechanical assembly and magnetic actuation of polydimethylsiloxane-iron composite interconnects for microfluidic systems

Abstract

We present magnetically-actuated micromechanical interconnects for microfluidic applications fabricated in-house using PDMS-iron elastomer-ferromagnetic composites (EFCs). Interconnects are fluid-tight, interlocking cylindrical posts and holes whose assembly can be made easier by magnetically actuating the EFC cylinders via axial extension and radial contraction. Towards this goal, we demonstrate magnetic actuation of interconnect structures, and quantify the mechanical disassembly of PDMS-iron interconnects without an applied magnetic field. Previously, we showed the mechanical assembly and disassembly of hybrid combinations of non-magnetic SU-8, silicon, and polydimethylsiloxane (PDMS) microfluidic interconnects. We fabricate EFCs for our interconnects by embedding iron microspheres (<63% by weight) in PDMS. We employed permanent magnets to create 0.045-0.065T constant fields, along with an optics test set-up that included a diode laser and magnification to quantify micron-sized deflections. The interconnects exhibited radial contractions of 3-12% and axial elongation of 2-11%. Without the magnetic field, disassembly forces of 36-71mN were measured by a controlled force linear actuator for PDMS-iron cylinders from PDMS and PDMS-iron holes. This work shows promise for radial contraction of cylinders for assembly with lower forces while maintaining high disassembly forces once the interconnects are assembled and the magnetic field is removed.