Title: A MEMS Micro Flowcytometer Based on Dielectric Particle Focusing and Integrated Optical and Impedanc
1A MEMS Micro Flow-cytometer Based on Dielectric
Particle Focusing and Integrated Optical and
Impedance Detection
Peter R.C. GascoyneDepartment of Molecular
PathologyMD Anderson Cancer CenterLi
ShiDepartment of Mechanical EngineeringThe
University of Texas at Austin
2Flow Cytometry
- Capability
- Measures physical and chemical properties of
single cells or other biological particles as
they flow in fluid stream past a light source - Analyze 105 cells per second
- Applications
- Analysis of blood cells, bacteria, nuclei,
chromosomes - Detection of cancer cells labeling of surface
markers - Measurement of particle size, shape, granularity,
etc. - Sort cells
3Basics of Flow Cytometry
Hydrodynamic Focusing
Purdue University Cytometry Laboratories
- Focus cells in suspension by sheath fluid
- Illuminate cells in the focused suspension stream
- Analyze cells by detecting scattered and
fluorescence light
4Motivation for a MEMS Microcytometer
5Principle of Dielectrophoresis
6Principle of Dielectrophoresis
7Principle of Dielectrophoresis
8Principle of Dielectrophoresis
9Principle of Dielectrophoresis
10Dielectrophoretic Particle Focusing
DEP forces can be used to focus, trap or repel
particles, enabling particle fractionation and
separation Fringing fields at electrode edges
provide DEP levitation forces in direction normal
to the electrode plane
11Design of the DEP focusing channel
Use negative DEP to focus cells in the central
region of the stream Integrate fluorescent and
impedance detectors into flow channel
12Electrode Fabrication
Top View of the Bottom Electrodes
Bus bars to provide AC electric field of 90?
phase difference, i.e. 0?, 90?,180?, 270?.
Bus Bar
Channel
Side View
Electrode
13Electrode Fabrication (Contd)
Deposit inter-metal dielectrics, etch holes
2
1
Deposit gold electrodes
Si Substrate
3
Fabricate similar electrodes on a glass wafer
Deposit and pattern gold layer and insulation
layer
4
Glass substrate
Same phase of the electric field
14Electrode Fabrication (Contd)
5
Deposit SU-8, pattern a channel
SU-8 channel
Bonding process to complete the channel
Side View
6
Glass
SU-8
Si
15Optical Detector Fabrication
Fiber coupled to a blue LED
A
Glass wafer
TiO2/SiO2 multilayer interference filter
SU8
Au/Ti contact pads
P-Si
Channel
p-n diode
A
A-A Side View
Flow in
Flow out
16Acknowledgement
- BME Seed Grant
- Graduate Student Choongho Yu, UT Austin