Bacterial Flagellar Motors as Microfluidic Actuators
Microfluidic actuators provide mechanical power to microfluidic systems. We are developing hybrid microfluidic systems that utilize flagellar motors in live, tethered Escherichia coli (E. coli) cells as microfluidic actuators. Examples of the hybrid systems under development include a micro dynamo and a micro pump. Each design utilizes the rotational power of tethered E.coli cells in a unique way to achieve an engineering application that is difficult to accomplish by a conventional microfluidic actuator.
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Carbon Nanotube DNA Biosensors
The research in this project represents a step towards the development of ultra-sensitive biosensors that will provide label-free, direct real-time electronic detection of DNA hybridization between surface immobilized single strand DNAs on multi-walled carbon nanotubes (MWCNTs) and target single strand DNA from a given bioagent. Simply put the nucleotide base pairs of DNA attached to the MWCNT will bind with complementary nucleotide base pairs of DNA from the bio or chemical agent to be detected.
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Chemiluminescence Detection of E. Coli O157:H7
A rapid and highly sensitive chemiluminescence biosensor based on a microfluidic filter chip for the formation of a monolayer of microbeads used in detecting E. coli O157:H7 was developed. The filter chip was fabricated by thermal fusion bonding of two microchannel chips to form a filter chip with different inlet (11.5 microns) and outlet depths (2.5 microns). Samples containing E. coli O157:H7 are incubated with immunomagnetic microbeads (8.27 microns diameter) and peroxidase labeled anti-E. coli O157:H7 antibodies to form a beads-bacteria-peroxidase labeled antibodies sandwich complex which was pumped into the filter chip using a syringe pump. With the stepped configuration of the filter, the outlet of the filter acts as a barrier and the microbeads can be separated from the suspension medium and spread in the microchamber as a monolayer. The monolayer of the beads maximized the optical accessibility of the E. coli cells to the detecting fiber optics when compared to conventional methods with multiple bead layers.
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Carbon Nanotube Shear Stress Sensor
This research is focused on the theory of alignment of CNTs during sensing element fabrication as well as experimental and calibration results from sensor testing. It is found that CNTs can be routinely aligned between surface micromachined gold electrodes using AC dielectrophoresis to form shear stress sensing elements. In order to fabricate the sensing element, a 25 Vp-p electric field at 3 MHz was used to form a ~150 µm wide line of aligned CNTs.
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Carbon Nanotube FET Devices
The purpose of this project is to deliver a low cost FET for future biosensors. Currently it has been shown that single semiconducting nanotubes can be built as logic gates or sensing devices. The current sensor that was fabricated although robust compared to other designs can offer more accurate reproducibility and a more economical way or manufacturing micro-sensors.
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Simulation of an Electrical Impedance Biosensor Using COMSOL
Biosensors are being used for highly sensitive and selective recognition of biological macromolecules. The impedance based biosensor utilizes the electrical impedance measurements between interdigitated electrodes integrated into a microchanel containing the target cells in a suspension medium. This project involves the simulation of electric impedance of an interdigitated microelectrode for detecting E. coli cells.
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