Fabrication Technologies

Despite the fact that nonlinearities are inherent in many natural and engineered systems, it is common for engineers to remove, or attempt to remove, all nonlinearity from their designs. Although this simplifies the performance analyses, it also overlooks a wide array of phenomena that could potentially enable fundamental breakthroughs.

The objective of this project is to derive fundamental insights for complex arrays of nonlinearly coupled oscillators, using structures defined as magneto-mechanical lattices. The magneto-mechanical lattices comprise periodic arrays of dynamically interacting magnets, which can be conceptualized as an array of equivalent springs and masses, or alternatively, as a solid composed of artificial macro-atoms. The nonlinear magnetic coupling is to be theoretically tailored to exploit nonlinear energy transfer behaviors, such as reconfiguring bandgaps, energy localization, internal resonances, etc. These nonlinear phenomena are to be experimentally demonstrated and measured by fabricated magneto-mechanical lattices.

Research Objective

To investigate the use of advanced microfabrication technologies and MEMS-enabled magnetization methods in developing reduced-scale permanent magnet undulator structures (with fine pole pitch ~5 microns) while maintaining reasonable magnetic field strengths as well as efficient generation of brilliant, high energy (>10keV) mono-energetic x-rays from modest electron beam source energies (~200MeV).

Theory

An accelerated beam of electrons with relativistic velocities experiences an undulation when passing through a spatially periodic magnetic field. This undulation of the beam trajectory results in the generation of electromagnetic radiation from which intense, tunable x-rays can be produced.

Technological advances in microelectrode neural probes have great potential to benefit patients with neurological diseases and injuries because they allow for direct interfacing and intervention with neurons of the nervous system. The interface design involves chronically collecting neural activity directly from the cortex of the brain, interpreting its information, and delivering therapy via an electronic interface. Such Brain-Machine Interface (BMI) systems that are capable of recording and processing the activity of large ensembles of cortical neurons have the potential to allow paralyzed individuals to communicate with the external world via computer control or direct control of prosthetic limbs and wheelchairs.We design, fabricate, and test flexible microelectrode array that can be hybrid-packaged with custom electronics in a fully implantable form factor to realize a self sustained BMI system. Also the flexible cable will provide strain relief to the implanted electrode and potentially improve long term viability.

This project aims at designing novel micromachining techniques for polymer-based flexible substrate microelectrodes as well as defining requirements for recording amplification, signal processing, and wireless telemetry systems. Much effort is going into the design and fabrication of highly compliant 2D electrodes which will potentially increase the possibilities of achieving reliable neural recordings over a chronic period . All efforts are in attempt to further the field of chronic neural recording for neuroprosthetic therapies.

Research Objectives

To develop a wireless shear-stress sensor array to provide three-dimensional, time-resolved, fluctuating skin friction data to aid turbulence model development.

Approach

Each sensor is effectively an LC tank made up of a variable-capacitance floating element and an integrated inductor. The sensing antenna is inductively coupled to the tank and can detect a change in the resonant frequency caused by a displacement of the floating element. An array is realized by designing each sensor to have it’s own unique resonant frequency. Then a single broad spectrum antenna can monitor the entire array.

Broader Impact

The realization of such an array will enable fundamental scientific studies of complex turbulent flows. It could also be implemented into a feedback control system for future air vehicles employing active flow control.

This project focuses on the development of a non-intrusive, direct, time-resolved wall shear stress sensor system for low-speed applications. The goals of the project include the fabrication and packaging of a 2-D wall-shear stress sensor with backside wire bond contacts to ensure hydraulic smoothness in flow environments. A differential capacitance transduction scheme is utilized with interdigitated comb fingers on each side of a suspended floating element, allowing for measurements to be made in both the positive and negative x- and y-directions.  A synchronous modulation-demodulation circuit is employed to simultaneously capture both mean and fluctuating shear content. Both AC and DC calibrations are performed to determine sensor sensitivity in both directions of transduction. This is the most successful effort of shear sensor development in published literature. 

The objective of the effort is to transition high-performance micromagnets into fully-integrated, batch-fabricated micromagnetic actuators for applications such as micro adaptive flow control.

Motivation

Magnetically-based electromechanical actuation schemes are ubiquitous in macroscale systems such as audio speakers, relays, solenoids, and electrical motors.  However, implementation of these transduction schemes at the microscale is nearly nonexistent because of certain design and fabrication challenges—primarily the inability to integrate high-performance, permanent-magnet (magnetically-hard) films within more complex micromachined structures.  As a result, most microfabricated transducers rely on other transduction mechanisms (e.g. electrostatic, piezoelectric, thermoelastic).  However, these mechanisms limit the actuation force, stroke (displacement), power density, and efficiency necessary for certain applications. 

The proposed actuator uses an adaptable and scalable actuation scheme, in that the device structure can be tailored for a wide range of applications.  Examples include micro pumps/valves for microfluidic (gas or liquid) systems; high power density motors/actuators for microrobotics; or low-profile acoustic radiators for navigations/sensing.  The evolution of fully-integrated micromagnetic transducers will enable performance improvements for existing applications and opportunities to explore new transformative technologies. 

Objectives

(1) to validate and characterize the integrability (chemical stability, temperature stability, mechanical reliability, magnetization methods etc.) of the permanent magnet materials in complex microfabrication process flows

(2) to model and optimize a multi-magnet out-of-plane microactuation scheme

(3) to fabricate and characterize a fully-integrated out-of-plane piston-type actuator that can be directly implemented as a micro aerodynamic control surface or adapted as a synthetic jet actuator 

(a)

(b)

Figure 1: CAD drawings of the proposed micro-electrodynamic synthetic jet actuator actuator: (a) Actuator assembly comprising two dies made from silicon substrate, separated by a separator. The top die is covered with a PDMS diaphragm and has a bonded powder magnet in the center. (b) Exploded view of the bottom wafer.

Increases in air traffic and tighter restrictions on noise pollution in and around airports have motivated research to reduce the aeroacoustic noise generated by aircraft.  Aeroacoustic testing with microphone arrays is used to identify and help design acoustic treatments on new and existing aircraft in order to reduce the noise signature of the aircraft.  The performance of a microphone array is a function of the number of microphones used, which is traditionally limited by the cost of each sensor.  Piezoresistive MEMS microphones take advantage of batch fabrication wafer processing to reduce sensor cost and achieve higher sensor packing densities in aeroacoustic arrays.  Thus, an increase in performance can be achieved for an equivalent, or possibly reduced, cost.

The goal of this research is to develop a pressure sensor and shear stress sensor that are able to provide continuous, time-resolved flow measurements within high temperature environments such as those seen in hypersonic wind tunnels and turbines.  A primary focus of this research is on the micromachining of sapphire using a picosecond laser.  Sapphire’s mechanical and thermal properties make it an ideal material for high temperature measurements.  Each sensor operates by mechanically deflecting under either a pressure or shear stress.  These deflections can then be detected using an opto-mechanical transduction scheme.  The completed sensors will be tested in flow cells and wind tunnels at UF as well as in other transonic and hypersonic facilities.

J-355PS Picosecond Laser Micromachining Workstation from Oxford Lasers