Hashemi invited to attend NAS symposium
Biosensors
Optofluidics
Renewable Energy
Bio-N/MEMS: Design, Modeling, and Fabrication
Diagnostics and Therapeutics
Physics of Micro/Nanoscale Phenomena
Nonlinear Dynamics
At the Hashemi Lab, we are working on projects concerned with the design and fabrication of microfluidic/optofluidic devices with applications to clinical diagnosis, renewable energy, and environmental monitoring.
Hydrodynamic focusing of one laminar stream by another has inspired new approaches in biosensors and cell analysis. We have devised a novel system to ensheathe, focus, and separate the sample stream from the sheath streams. Using grooves at very specific orientations in the upper and lower surfaces of the microchannel, the sheath fluid is directed around the sample stream in the microflow cytometer. The dynamics of fluid flow can be reversed by reversing the direction of the forces applied to the system at low Reynolds number. Integrating the concept of “unstirring” into the groove-based sheath flow system by placing reverse grooves in the channel pointing upstream, the sample stream is separated from the contiguous sheath streams. The unsheathing capability provides the opportunity to recover particles from the sensor with minimal dilution or to recycle the sheath fluid for long-term unattended operation. Flow cytometers with recycled sheath fluid could be used to monitor recycled drinking water for bacterial contamination on the space shuttle or to reduce the size and logistical burden of systems that monitor the air for release of biothreat agents. Also, circulating tumor cells could be concentrated for culture or genetic analysis after identification by flow cytometry without immunomagnetic separation or centrifugation.
Phytoplankton are marine microorganisms that respond very rapidly to environmental changes. As such, changes in phytoplankton populations can be measured in response to introduction of environmental pollutants, alterations in ocean currents, and global climate change. Flow cytometry has been deployed to look at individual phytoplankton and to more accurately assess population changes. We have developed a cytometer-on-a-chip that uses grooves to direct the sheath fluid completely around the sample stream. Optical fibers inserted into the microchannel interrogate each cell in the sample stream at four different wavelengths. Fluorescence as well as side scattering properties of the species are used to discriminate different populations of phytoplankton. Results of this research will be used for in situ marine particle exploration on unmanned underwater vehicles (UUVs).
Deidre
Sechi, freshman in mechanical
engineering, spent this past summer involved
with the Summer Program for Enhancing
Engineering Development (SPEED) program. During
her time in the program, Sechi was involved with
research on
paper-based microfluidic devices
under assistant professor Nastaran
Hashemi.
"Dr. Hashemi showed me how I could combine a mechanical engineering degree with the medical field," says Sechi. (Full story)
Hashemi receives NRC/ASEE research publication
award for optofluidic approach
Nastaran Hashemi, William March Scholar in Mechanical Engineering, was chosen to receive the 2011 Naval Research Laboratory NRC/ASEE Research Publication Award for her paper “Optofluidic characterization of marine algae using a microflow cytometer.” (Hashemi publication award release)
Pursuing New
Ideas
Being the William March
Scholar in Mechanical Engineering at Iowa State
University is much more than just a prestigious
title. Nastaran Hashemi was
named the latest March Scholar this past fall,
and she has hit the ground running with the
funding that the award provides her. (Full
story)
