Mass spectrometry is the determination of the elemental and molecular composition of a substance by measuring the mass to charge ratios of ions.
Current mass spectrometers are bulky and immobile so there is a need to create a reliable but portable system. The development of a portable system will facilitate many desired applications of mass
spectrometers including but not limited to space exploration, military intelligence, and counter terrorism initiatives.
Ion traps utilize electric fields to create a trapping region. IMMERSE students helped develop an enhanced design using an open ring shape that allows for superior control of the trapping field, which improves resolution and accuracy so that the detection of different isotopes is possible.
Sacrificial Microchannels for Electroosmotic Pumps and Separation Devices
- Mark N. Hamblin, Aaron R. Hawkins, John M. Edward, V. Milton, L. Lee, Adam T. Wooley
Microfluidics involves any fluid manipulation on a microscale. Most microfluidic systems developed to date involve expensive and time-consuming wafer-bonding techniques and so the development of sacrificial microchannels has become an important project. For sacrificial microchannels, one layer is put down first in the place where the channel is wanted and another material is put over the top of it. The inner material is dissolved and an open channel is left. The total fabrication process takes about a week.
Electroosmotic pumps are used to move fluids through these microchannels. They work because some materials generate a mobile charged layer in the presence of a solution. When an electric field is applied across the channel length, the mobile layer migrates to one of the electrode and effectively drags the solution with it. I was found that the EO pumps are most effective when they consist of multiple parallel bands and are short rather than long.
Zero Power Shock Sensors Using Bistable Compliant Mechanisms
- Brett Hansen, Christopher Carron, Stephen M. Schultz, Aaron R. Hawkins
Damaging impacts occur with materials such as cell phones or computers everyday but currently there is no device to monitor the impact. Because you would have to power them, it would be very unpractical to attach electronic shock sensors to every item. Therefore, a new shock sensor, using a bi-stable compliant mechanism has been developed.
The mechanism has two stable positions and works on a beam bulking concept. It will switch from one position to the other when acceleration exceeds a certain amount and remain there, allowing the device to be easily read by any one. This shock sensor is extremely inexpensive and can be used for any component or system that is sensitive to shock or impact.
On-Chip Atomic Vapor Cells
- John F. Hulbert, Brandon T. Carroll, Aaron R. Hawkins, Bin Wu, Holger Schmidt
Atomic vapor cells are used to investigate optical effects such as frequency reference for atomic clocks, precision spectroscopy, gas phase sensing, low-level switching, and electromagnetically induced transparency. Most atomic vapor cells are relatively large and require large and complex systems to build and analyze. By having an on-chip atomic vapor cell, the total area used can be greatly reduced. Also, by using a hollow core waveguide, the nonlinear interaction length can be greatly improved.
The on-chip atomic vapor cells utilize on-chip hollow waveguide technology. The hollow core is filled with "atomic vapor" by sealing one end of the core with epoxy and attaching a reservoir containing Rb on the other side. The reservoir is then evacuated to prevent pressure broadening in our spectral plots. Once the vapor cell has reached the desired pressure, the reservoir is sealed. Based on the photon-atom interactions, one can perform spectroscopy by observing how the atom absorbs electromagnetic energy around transitions and how the intensity of light near resonant frequency changes as it propagates through the vapor.
Liquid Filled Optical Waveguides for On-chip Chemical Analysis
- Evan J. Lunt, Brian S. Phillips, Aaron R. Hawkins, Philip Measor, Sergei Kuehn, Holger Schmidt
Fast analytical tools to study and analyze single biomolecules on the nanoscale are of paramount importance in molecular biology. A primary method is based on florescence detection which requires single-molecule sensitivity and selection and the capability to analyze large numbers of sample molecules simultaneously or within a finite amount of time. To provide these requirements, lab-on-a-chip platforms are being created. Optofluidic labs-on-a-chip are compact, low cost, require only a small sample size and have integrated detection and excitation features. Applications of what is basically a portable lab, include virus detection at the outbreak sites, low cost clinical diagnostics, and measurements of DNA or other biomolecule charatereistics.
In a classical waveguide, light is confined and directed through Total Internal Reflection,but this becomes difficult if one wants the core to contain liquid or gas. Hollow waveguides can be made by surrounding a space with mirrors in very careful layers of silicon dioxide and silicon nitride.Liquid-filled hollow waveguides are crossed with solid waveguides and molecules floresce as they pass through this intersection. These bursts of light are collected and used in analysis.
Integrated Hollow-Core Waveguides made by Sputter Deposition
- Yue Zhao, Evan J. Lunt, aaron R. Hawkins, Holger Schmidt, Donghang Yen
Optical sensing using integrated waveguides on chips can be applied to many fields. It can be difficult to guide waves within liquids or gases because of their low indexes. ARROW stands for Anti-Resonant Reflecting Optical Waveguide and it confines leaky modes to the liquid or gas core by using high-index cladding layers.
To create ARROW based sensors faster and cheaper, a new fabrication method has been developed that relies on sputtering instead of PECVD. PECVD requires high temperatures, a long removal and then has a low efficiency. Sputtering is done at lower temperatures, the thickness is more easily controlled, and it can be done on one machine instead of two. SU8 is used for a strong outer layer but is has a few problems like it will occasionally "lift up". In the future, alternate overcoat layers will be explored and platforms integrating the ARROWs will be created.
Micropore and Nanopore Features on Integrated Hollow Waveguides
- Matthew R. holmes, Tao Shang, Aaron R. Hawkins, Mikhail Rudenke, Holger Schmidt
Hollow waveguides are useful in many applications for two reasons: 1)light guiding is accomplished without total internal reflection and 2)light can be guided in very low index media like air or water. This allows for high optical intensity light to interact with solid or liquid media over long distances. ARROWs produces both solid and hollow core waveguides.
For fluid-sensing applications, it is desirable to have access to the fluid-filled core of the hollow waveguide to regulate and regulate the analyses flowing into it. This is accomplished by drilling a micropore feature on top of the hollow waveguide while leaving intact a small nitride membrane. A nanopore feature can then be drill inside the micropore. These micropores and nanopores allow one to perform single molecule detection. They selectively filter analyses according to size.
Solid State Impact Ionization Multiplier
- Joshua Beutler, Michael Johnson, Alan Nelson, Aaron R. Hawkins
Avalanche multiplication based current amplifiers can be produced on a microscale and are commonly used today. The nature of these devices requires the detectors and the amplifiers to be combined. Many materials are great for detection but bad for amplification and others are great for amplification but detect only a small range of wavelenths. I t would be benficial ot develop a highly sensitive solid-state impact-ionization based current amplifiers which can be integrated with an arbirary current source. This would make it possible for the signal from a photodiode designed for maximum efficiency at a given wavelength to be amplified without concern for material compatability.
When charge carriers are introduced into a strong E-field, they acquire sufficient energy to knock electrons off atoms creating electron hole pairs. An arbitrary current source injects electrons into a depletion region produced by the reverse biased diode between the output electrode and ground. When electrons reach the high field region impact-ionization occurs. The electrons are drawn to the N+ dope region and the hole are drawn to the P+ region.
Non contact Scanning Electrical Impedance Imaging
- Tao Shang, Hengze Liu, Aaron R. Hawkins, Steven M. Schultz, Travis E. Oliphant
We are interested in applying electrical impedance imaging to biological samples as small as a single cell because it has the potential to reveal both cell anatomy and cell function. However, classic imaging techniques are not applicable because of their low resolution so we developed a new method of impedance based on a non-contact scanning system -- Scanning Impedance Imaging. The imaging sample is immersed in an aqueous solution allowing for the use of various probe designs.
