OSTE+ Polymer Composite with Rare Earth Hard Magnetic Particles for Flexible Reaction Injection-Moldable Microfluidic Actuators

We present a novel magnetic composite polymer (M-CP) that consists of off-thiol-ene-epoxy (OSTE+) polymer thermoplastic resin embedded (doped) with rare earth (hard) magnet particles, resulting in an M-CP that is flexible and capable of strong, bi-directional actuation. While previously shown for microfluidics, OSTE+ has not yet been embedded with functional (e.g., magnetic) particles. We demonstrate that a magnetic OSTE+ using a matrix polymer of OSTEMER 324 Flex embedded with 25% by weight rare earth ((Nd0.7 Ce0.3)10.5Fe83.9B5.6) magnetic powder remains flexible after photopatterning, can be permanently magnetized, and retains a permanent magnetic field for at least 15 months. We develop a fabrication flow for this new material, as well as determine its ultraviolet (UV) curing times. Further development of magnetic OSTE+ could advance the integration of flexible M-CP microactuators into mass-manufacture, as OSTE+ integrates well with diverse substrates and can be tailored to have different ranges of Young's modulus, allowing for flexible actuators to be built into an otherwise rigid device.