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ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
A STUDY ON CELL ADHESION BY A STUDY ON CELL ADHESION BY USING MEMS TECHNOLOGYUSING MEMS TECHNOLOGY
Rui Qiao Xiaohui TanME-381 Dec. 5
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Presentation Outline
• Introduction and motivation• Current MEMS systems in this area• Our idea• Conclusion
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Meaning of this research
• Understand the evolution of tissues and organs • Manipulate the adhesion
http://health.allrefer.com/
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Why MEMS?
• Cells and MEMS are in the similar scale
• Cells can survive on artificial surfaces
• The microfabrication technique is relatively mature
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Model I
In-situ adhesion studies of a single living bovine endothelial cell using MEMS sensor
The MEMS sensor consists of a cantilever beam madeof Single Crystal Silicon (SCS), 1200 µm long x 11.5 µm deep x 4 µm wide, coated by a thin native silicon dioxide layer.
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Experimental System
Microscope Objective
Endothelial Cell
MEMS Cantilever
PiezoActuator20 nm Resolution
X-Y-Z Stage
1 m Resolution
1 m Resolution
Liquid Media
Tissue Culture Dish
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Experimental Result
The adhesion properties of a single living bovine endothelial cell was studied. Quantitatively it has been found that a focal adhesion site, prior to failure, applies 37 nN of force onto the MEMS sensor.
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Discussion
• This work is one of the earliest studies on cell adhesion.
• The device is quite simple and they can measure the magnitude of the adhesion force
• This device doesn’t have much control on the contact of the cell and the beam
• Can only measure the force form on contact region
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Model II
Cells lying on a bed of microneedles: An approach to isolate mechanical force
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Strategy
A strategy to independently manipulate mechanical compliance and surface chemistry:
for small deflections, the deflection is directly
proportional to the force applied by the attached cell
3
3
L
EIF
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Result
Both the magnitude and direction of the adhesion forces can be obtained
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Advantages
• Less assumptions• Can capture the magnitude also the direction of
the force at the same time • The mechanical property of the substrate can
be easily changed without change the material of the substrate
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Disadvantage
• The resolution of this model only in micrometer scale while the focal adhesion is also in this scale
• Improving the resolution means increasing the density of posts in the array, which leads to a high requirement of deflection measuring precision
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Our idea
• Use the membranes to measure the focal adhesion forces. As the deformation is vertical, the dots could be very close without any interactions
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ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
MEMS System
Cell
MembraneMembrane
Fabricate an array of membranes on a silicon wafer. Those membranes will deform under cell adhesion
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Fabrication process
wafer1 wafer2
hydrophobicalkanethiol
protein-resistant hydrophilic alkanethiol
• Photolithograph• Cast PDMS• Electrical etching• Microcontact
printing
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Measurement
Photo Detector
Beam splitterLaser Beam
Use optical readout to detect the displacement of each Use optical readout to detect the displacement of each membranemembrane
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Discussion
• Advantage– Can improve the spatial resolution – Can determine the adhesion force from each
focal contact site. • Disadvantage
– Cannot get the direction of the force – Readout device is complicated
ME-381 Dec. 5 Xiaohui Tan, Rui Qiao
Conclusion
• Introduced two MEMS system already used.• Provided a new device, which needs experiment
to prove• With the size of device decreasing, NEMS
system will act important roles in this area