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Magnetostrictive Materials

Magnetostrictive materials exhibit coupling between magnetic and mechanical energies. Magnetostrictive materials exhibit mechanical deformation when driven by a magnetic field or vice versa. Therefore, they can be employed for actuation, sensing, and energy harvesting. All ferromagnetic materials exhibit the magnetostrictive effect, but only certain iron–rare earth alloys, iron–gallium alloys, amorphous metals, and iron‐ aluminum alloys exhibit sufficiently high magnetostriction for commercial use. Magnetostrictive materials are suitable for harsh environments (i.e., high temperature, radiation) and biomedical applications.

Ultrasonic waveguide thermometer (Active)

Sponsor: DOE Advanced Sensors & Instrumentation (ASI) Program

(a) Physical assemble of the pulse-echo mode ultrasonic thermometer with an additional DC bias coil. (b) 2D axisymmetric model layout in COMSOL Multiphysics. (c) Simulated compressive wave propagating in the Galfenol wire (40 microseconds after excitation).

Ultrasonic thermometry has the potential to improve upon temperature sensors currently used for in-core temperature measurements. Ultrasonic thermometers (UTs) work on the principle that the speed at which sound travels through a material (acoustic velocity) is dependent on the temperature of the material. Temperature may be derived by introducing a short acoustic pulse to the sensor and measuring the time delay of acoustic reflections generated at acoustic discontinuities along the length of the sensor. UT temperature measurements may be made near the melting point of the sensor material, allowing monitoring of temperatures potentially in excess of 3000°C.

The figure above shows a typical UT design based on iron-gallium alloys or Galfenol. We have developed an accurate and efficient multiphysics model that is able to capture the acoustic wave propagation in the waveguide.

Additive manufacturing of magnetostrictive materials

Sponsor: NASA Idaho Space Grant Consortium (ISGC) grant

(a) Configuration of magnetostrictive beam actuator, (b) magnetostrictive cobalt-ferrite beam printed by nScrupt SmartPump; and (c) Tip deflection of the cobalt ferrite beam under varying magnetic field.

Our group has successfully printed magnetically-active composites by dispersing magnetostrictive particles in polymeric matrices. By printing magnetostrictive composites on top of passive substrates, we further developed cantilever actuators, also known as unimorph actuators, as shown in the figure on the left. When a magnetic field is applied along the longitudinal direction of the beam, the magnetostrictive layer deforms while the passive substrate tends to maintain flat. Therefore, the unimorph actuator outputs micro-scale and butterfly-shape tip deflection. This actuator can be potentially used for precision drug delivery or optical instrument control.

Piezoelectric Materials

Piezoelectric materials exhibit coupling between electrical and mechanical energies. As a result, piezoelectric materials can output significant deformation instantaneously when subjected to an electrical field. Therefore, they have been widely used as high frequency and large power density actuators. On the other hand, electric charges accumulate on the surface of piezoelectric materials when they are subjected to mechanical loadings. Therefore, piezoelectric materials have been utilized as structural vibration energy harvesters and sensors. Our lab focuses on piezoelectric ceramics (e.g., PZT, barium titanate) and piezoelectric polymers (e.g., PVDF, PVDF-trFE).

All-printed tactile sensor (Active)

Sponsor: SEMI FlexTech

piezo tactile sensor
(a) Configuration of a P(VDF-trFE) piezoelectric tactile sensor; (b) all-printed piezoelectric tactile sensor.

A typical piezoelectric tactile sensor consists of a piezoelectric layer (e.g., PVDF-trFE) sandwiched by a pair of electrodes, as shown in the figure on the left. Our group has printed the PVDF-trFE layer and top silver electrode. In collaboration with Dr. Benjamin Johnson (Boise State), our group has developed signal processing and wireless data transmission circuits for piezoelectric sensors for the purpose of measuring carotid pulses.

Printed surface acoustic wave (SAW) sensors

Sponsor: DOE Advanced Sensors & Instrumentation (ASI) Program
(Under construction)

Shape Memory Materials

Shape memory materials exhibit coupling between thermal and mechanical energies. Specifically, our group focuses on shape memory polymers that can return from a deformed shape (temporary shape) to the memorized shape (permanent shape) when they are heat up beyond the transformation temperature. This unique property has enabled innovations in morphing structures, actuators, and self-healing structures.

printed shape memory polymer
Printed shape memory polymers morphing between a 3D rose shape and a 2D Bronco logo.

Our group has printed shape memory polymer structures that exhibit more than 60% deformation at a transformation temperature of around 70 °C. The figure on the left shows a printed morphing structure transforming between 2D Bronco logo and 3D rose shape. The video below shows a morphing electrical circuit printed on top of shape memory polymers.

Multiphysics Modeling

Multiphysics Modeling of Surface Acoustic Wave Transducers

Constitutive model for Terfenol-D

(Under Construction)

Finite element model for LVDT (Active)

Sponsor: DOE Advanced Sensors & Instrumentation (ASI) Program

Linear Variable Differential Transformers (LVDT) sensors
(a) A CT image showing the cross section of a Halden LVDT sensor. (b) 2D axisymmetric model configuration in COMSOL Mutiphysics. (c) Magnitude of magnetic flux density in Tesla when the core is 1 mm away from the null position.

Linear Variable Differential Transformers (LVDT) sensors, known for superior in-pile performance under irradiation, are available to provide micron-scale resolution data enabling the evaluation of fuel performance. Such a high resolution measurement requires a careful understanding of not only sensor itself, but also the complete implementation strategy, including thermal conditions, hardware selection and design, and data processing. To evaluate sensor performance, reduce sensor size, and optimize sensor configurations, this study first develops a finite element model in COMSOL Multiphysics for commercial LVDT sensors in order to investigate the impact of each component’s dimensions and material properties. This study then establish a finite element model including a through hole at the LVDT core to allow for instrumentation pass-through, such as a fiber optic cable.

Sponsors and Collaborators

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