Biomaterials for MEMS

220 References

(Fig. 9.8(a)) and 4-hour incubation (Fig. 9.8(b)) shows that the 4-hour incubated

sample has ∼69.5 % higher protein adsorption than the 1-hour incubated sample.

Neverthless, vibration removed most of the adsorbed

9.6 CONCLUSIONS AND OUTLOOK

A novel anti-fouling mechanism based on the combined effects of electric field and

shear stress is reported. The mechanism was observed in mm scale piezoelectric

plates coated with different metal materials and MEMs (MicroElectroMechanical

system) fabricated membrane based device. The piezoelectric material, lead

zirconate titanate (PZT) composite, coated with electrodes after application of

voltage (DC or AC) can (1) accumulates the surface charges, which generates

an electric field against proteins adsorption (with the similar charge of proteins);

and (2) induced an acoustic streaming shear stress, which attenuates the desorp-

tion of proteins. In vitro characterization showed that 58 ± 5.5% of adsorbed

bovine serum albumin (BSA) can be effectively removed from PZT. Theoretical

calculations of protein-surface interactions (van der Waals (VDW), electrostatic,

and hydrophobic) and shear stress reveal the mechanism of attenuation of protein

(BSA) adsorption.

On the other hand, a micromachined vibrating membrane is proved to be able

to attenuate proteins adsorption as well. The (2000 μm x 500 μmx3μm) silicon

membrane attached by a lead zirconate titanate (PZT) composite (3 mm × 1mm

× 0.5 mm) can vibrate in a FPW, which is also verified by FEM simulation. The

surface charges on the membrane and the fluid shear stress contribute in reducing

protein adsorption on the membrane surface. In vitro characterization shows that

57±10% of the adsorbed BSA, 47±13% of IgG, and 55.3∼59.2±8% of the blood

plasma proteins are effectively removed from the vibrating membrane. Potentially,

a microelectromechanical system (MEMS)-based vibrating membrane could be a

tool to minimize biofouling of in vivo implants.

ACKNOWLEDGMENTS

This work was supported by the Natural Sciences and Engineering Research

Council of Canada (NSERC), Canada Foundation for Innovation (CFI). I would

like to thank Dr. M. Chiao, and Dr. J. N. Kizhakkedathu for the valuable comments

on the early drafts.

References

1

M. Schlosser and M. Ziegler, in Biosensors in the Body: Continuous in vivo Monitoring,

Ed. D. M. Fraser (John Wiley & Sons, Chichester, 1997).

2

D. M. Fraser, in Biosensors in the Body: Continuous in vivo Monitoring, Ed. D. M. Fraser

(John Wiley & Sons, Chichester, 1997).

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