me-381 dec. 5xiaohui tan, rui qiao a study on cell adhesion by using mems technology rui qiao...

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


Presentation Outline

• Introduction and motivation• Current MEMS systems in this area• Our idea• Conclusion


Meaning of this research

• Understand the evolution of tissues and organs • Manipulate the adhesion

http://health.allrefer.com/


Why MEMS?

• Cells and MEMS are in the similar scale

• Cells can survive on artificial surfaces

• The microfabrication technique is relatively mature


Some of Current Models

Single MEMS sensor

A bed of microneedles


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.


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


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.


Focal adhesion

• Procession of a breaking filopodia


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


Model II

Cells lying on a bed of microneedles: An approach to isolate mechanical force


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

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Fabrication


Fabrication Cont’d


Result

Both the magnitude and direction of the adhesion forces can be obtained


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


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


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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MEMS System

Cell

MembraneMembrane

Fabricate an array of membranes on a silicon wafer. Those membranes will deform under cell adhesion


Fabrication process

wafer1 wafer2

hydrophobicalkanethiol

protein-resistant hydrophilic alkanethiol

• Photolithograph• Cast PDMS• Electrical etching• Microcontact

printing


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


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


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


ACKNOWLEDGEMENT

Professor Horacio D. Espinosa

TA: Yong Zhu

Team members

me-381 dec. 5xiaohui tan, rui qiao a study on cell adhesion by using mems technology rui qiao...

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