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The goal of this project is to develop thermally actuated and manufactuable microfluidic valves for a variety of applications. The valves can be integrated in a device; the actuation of valves will be controlled by a printed circuit board (PCB). The valves are expected to be useful in any system that needs flow controls and fluid metering. The project has been funded by Defense Advanced Research Projects Agency (DARPA), and a project for an immunoassay array involving a number of microvalves is currently funded by National Institute of Health (NIH).  More info can be found in this link: http://www2.mae.ufl.edu/%7Ehfan/Research.html

Our research goal is to develop photoresponsive shape memory polymers (SMPs) that incorporate cinnamic acid and cinnamylidene acetic acid which are able to undergo efficient photoreversible reactions when exposed to alternating wavelengths of light. The hope is that this reversible reaction will be used to actively cleave and reform covalent crosslinks to mitigate the propagation of damage though local fracture, achieve shape recovery for crack closure, and to ultimately reform crosslinks across the crack face to recover the strength of the original material.  Our current results have shown that we can produce 1200% increased toughness, recover the plastic deformation of the specimen following loading to return it back to its original dimensions and subsequently achieve 96% healing efficiency without the reformation of crosslinks in the polymer.  This work was featured live on CNN and various other news outlets.

This approach is novel in that using adaptation of the local stiffness to mitigate the propagation of damage followed by healing has not been studied in the literature; therefore this work has the potential to make significant advances in the design of autonomous structures and in the development of greater post-treatment measures concerning fractured areas. The effort from this research will ultimately provide methods to create materials that function and respond to damage; mimicking what some biological systems naturally do.

High energy density capacitors are critically important in advanced electronic devices and electric power systems that require bursts of large energy such as pace makers, defibulators, rail guns, electric vehicles and electromagnetic armor.  Our work is studying the use of nanocomposites to create ultra high energy density capacitors with particular focus on the role the morphology and orientation of the filler plays on the energy density.  Our current results have produced nanocomposites with energy density exceeding 10 J/cc, which is more than twice as large as high performance commercial materials.  Efforts to create further gains are focused on the synthesis of new high dielectric ceramic nanowires, approaches for the functionalization of the fillers to achieve improve compatibility with the polymer matrix materials and fabrication approaches to create the highest energy density capacitors available.

Experimental and numerical results over the past decade have conclusively demonstrated the effectiveness of turbulent drag reduction (up to 40%) through near-wall control schemes such as oscillating walls and traveling waves. However, these promising results have yet to lead to a suitable surface for practical application. We are developing a new near-wall turbulence control technique based on a recently developed nanowire surface, composed of vertically aligned Barium Titanate (BaTiO3) nanowires. Since BaTiO3 is a highly coupled piezoceramic, the surface can be manipulated by application of an electric field; and conversely the surface generates an electric potential in response to an applied mechanical load. We have hypothesized that actuation of the nanowire surface can produce cross-stream motion that will alter the structure of the boundary layer over the nanowire surface, resulting in modification of the wall shear stress. This hypothesis is based on recently improved understanding of the correlation between low-speed streak instability and the generation of drag-inducing streamwise vortices; suppressing these vortices at their onset by transverse motion controls within the viscous sublayer has proven extremely effective at stabilizing the low-speed streaks, leading to significant drag reduction.

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.

The objective of the effort is to design a compact Bluetooth/UWB antenna design with 5GHz WLAN notchi function.

Motivation

Among short-range wireless communication systems, Ultra-wideband (UWB) technology, with a frequency allocation of 3.1-10.6 GHz, has gained a lot of popularity from  researchers and the wireless industry alike due to the high data transfer rate (110-200 Mb/s) and low power consumption. However, since UWB covers the frequency spectrum of Wireless Local Area Network (WLAN) operating at 5.2 GHz (5150-5350 MHz) and 5.8 GHz (5725-5825MHz), a frequency notched function in the UWB antenna design is greatly desirable to avoid interferences from WLAN. Since 2002, various antenna structures and methods to notch a specific frequency band have been introduced. Moreover, a planar integrated antenna working on both Bluetooth and UWB has been recently introduced for systems operating in those two communication systems.

Objectives

(1) UWB antenna design

(2) 5GHz frequency notch function

(3) Integrate Bluetooth antenna

The objective of the effort is to design a high gain circular polarization antenna using metamaterial slabs for satellite communication.

Motivation

Mordern satellite communication systems often demand low-profile, wide bandwidth, high gain and circular polarization antennas. Traditionally, a reflector antenna, a horn antenna, and a microstrip array antenna are widely used to achieve high gain circular polarization. Recently, a metamaterial approach has been emerged as a promising method for a high gain antenna. However, a high gain circular polarization antenna using metamaterial remains as a big challenge.

Objectives

(1) High gain antenna with metamaterial slabs

(2) Circular polarization for satellite communication systems

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.

Directed energy applications require accurate and efficient transmission of optical energy to an intended target. A three dimensional turret design consisting of a hemispherical top with a flat aperture  has proven to provide a convenient method of pointing and tracking lasers from airborne platforms. However, the turret's three-dimensional blunt design leads to complex separation phenomena which, in turn, leads to distortion in an otherwise planar emerging laser beam. This research proposes to develop an adaptive feedback control system to control the flow field around the turret in order to improve aero-optic performance.

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.