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 55.359.2±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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