A MEMS-based electromagnetic membrane actuator utilizing bonded magnets with large displacement

In a previous study, microfabricated bonded magnets have been utilized in MEMS-based electromagnetic membrane actuators (EMMAs) to drive micropumps. However, to maintain the flexibility of the membrane the packing density of the spin-coated bonded magnets needed to be small (6 vol%) and this together with a strong self-demagnetization effect meant that the force generated was weak. As a result, the maximum displacement achieved was only several microns. To overcome this problem, we proposed fabricating bonded magnets using micro compression molding with a soft membrane mold in order to realize both a high packing density and a flexible membrane. The grooves (0.3 mm × 5 mm × t0.3 mm) in the PDMS membrane were filled with a mixture of NdFeB magnetic powder and wax powder. A packing density of 50 vol% for the bonded magnets was realized without undue influence on the flexibility of the membrane. A fine-pitch magnetization pattern was also used to decrease the self-demagnetization effect and thereby improve actuator performance. The experimental results show that the maximum force generated and the maximum displacement achieved using the fabricated EMMAs (12 mm × 12 mm × t1.1 mm) were 2.2 mN and 100 μm, respectively, at the power consumption of 4 W.