Micromachined magnetoelastic sensors and actuators for biomedical devices and other applications

Magnetoelastic materials exhibit coupling between material strain and magnetization; this coupling provides the basis for a number of wireless transducers. This thesis extends past work on microfabricated magnetoelastic sensors in three ways.;First, a new class of strain sensors based on the DeltaE effect are presented. Two sensor types are described -- single and differential. The single sensor has an active area of 7x2 mm2 and operates at a resonant frequency of 230.8 kHz with a sensitivity of 13x10 3 ppm/mstrain and a dynamic range of 0.05-1.05 mstrain. The differential sensor includes a strain-independent 2x0.5 mm2 reference resonator in addition to a 2.5x0.5 mm2 sensing element. The sensor resonance is at 266.4 kHz and reference resonance is at 492.75 kHz. The differential sensor has a dynamic range of 0-1.85 mstrain, a sensitivity of 12.5x103 ppm/mstrain, and is temperature compensated in the 23-60°C range.;Second, fluidic actuation by resonant magnetoelastic devices is presented. This transduction is performed in the context of an implantable device, specifically the Ahmed glaucoma drainage device (AGDD). Aspherical 3D wireless magnetoelastic actuators with small form factors and low surface profiles are integrated with the AGDD; the fluid flow generated by the actuators is intended to limit cellular adhesion to the implant surface that ultimately leads to implant encapsulation and failure. The actuators measure 10.3x5.6 mm 2 with resonant frequencies varying from 520 Hz to 4.7 kHz for the different actuator designs. Flow velocities up to 266 mum/s are recorded at a wireless activation range of 25-30 mm, with peak actuator vibration amplitudes of 1.5 mum.;Finally, detection techniques for improving the measurement performance of wireless magnetoelastic systems are presented. The techniques focus on decoupling of the excitation magnetic signal from the sensor response to improve measurement sensitivity and noise immunity. Three domains -- temporal, frequency, and spatial -- are investigated for signal feedthrough. Quantitative results are presented for temporal and frequency domain decoupling. Temporal decoupling is used to measure strain sensors with resonant frequencies in the 125 kHz range, whereas frequency domain decoupling is implemented to measure 44 kHz magnetoelastic resonators.