The Development of a Rotational Magnetic Actuator to Measure Platelet Biomechanics

Abstract

Platelets play an important role in the hemostasis process, which prevents blood loss in the event of injury. As platelets active and aggregate in response to vascular injury, they generate forces that are critical for forming a stable clot. Currently, there are few technologies that can isolate and quantify the forces that platelets generate. Recently, a microfluidic device has used rigid blocks and flexible posts fabricated with PDMS to induce platelet activation and measure their forces using the post deflections. By embedding the posts with magnetic microparticles, external forces could be applied on the posts using a permanent magnet. Using a slider system, static measurements of post deflections could be taken, during which a magnetic field was acting in an “on” or “off” state. To be able to take dynamic measurements of the microposts under force in real-time, the permanent magnet movement needed to be motorized. To develop such a system, a stepper motor was used to rotate a torque magnet about its axis such that it switched its magnetic dipole. This produced a dynamic magnetic gradient that could be used to apply an oscillatory force on the microposts. The rotating magnetic actuator was tested on the microfluidic devices in an air medium and showed that it could apply a stable and repeatable magnetic force on the microposts. Moreover, various inputs could easily be programmed to test a wide variety of mechanical properties. In the future, this device can be used to measure the biomechanical properties of platelets as they aggregate in real-time.