Biomedical microdevices include any miniaturized devices or systems for
biomedical or biological applications, from simple sensors for monitoring a
single biological, to complex micro total analysis or lab-on-a-chip instruments
that integrate multiple laboratory functions together with microfluidic sample
manipulation. Biomedical microdevice and systems research is an exciting
multi-disciplinary field intersecting engineering, physics, chemistry,
nanotechnology and biotechnology.
Micromachining, originally based in the microelectronic industry, forms the
foundation for this exciting field, in which biosensors, microchannel fluid
transport, and other micro mechanical, optical, chemical, and fluidic components
are fabricated and integrated for applications ranging from monitoring biofluid
levels and bed side rapid diagnosis to studying single cell antibody production.
Furthermore, micromachining can be combined with nanostructures or nanomaterials
to result in new technologies and techniques that continue to advance the field
in new ways.
The Microinstrumentation Lab
(µiL) at Simon Fraser University (SFU), under the direction of Professor Bonnie
Gray, develops a wide variety of biomedical microdevice and system
technologies and techniques. While conventional silicon is still employed,
micromachining of polymers and glass has taken center stage driven by
applications in biomedicine and biology.
Polymers can be employed for highly flexible microinstrumentation that can
conform to the body or other surfaces, that is optically transparent,
biocompatible, with inexpensive prototyping and easy micropatterning (e.g.,
micromolding, uv-light photopatterning). Glass is similarly optically
transparent and biocompatible, and makes an excellent substrate for polymer
Researchers at Microinstrumentation Lab (µiL) are developing free-standing
snap-together polymer microfluidic systems with flexible electronic interconnect
and on-board microactuators for micropumps and valves. While thin film
metal-on-polymer techniques have been successfully demonstrated for electronic
routing1, another approach avoids mechanical
materials mismatch by employing hybrid combinations of insulating polymers with
conductive nanocomposite polymers (C-NCPs). While flexible polymers are
inherently electrically insulating, conducting nanoparticles added to a polymer
matrix result in conduction once the percolation threshold has been
The Microinstrumentation Lab
(µiL) is developing new techniques to micropattern complete functional
systems using hybrid combinations of conducting and nonconducting polymers
(Figure 1). In addition to conductive polymers, magnetic polymers can be
realized with the addition of magnetic nanoparticles to a flexible polymer
matrix. Such magnetic polymers are employed by Microinstrumentation Lab (µiL) for assisting in micro
peg-in-hole chip-to-chip microassembly3, or on-chip
Figure 1. Flexible
conductive nanocomposite polymer embedded in an insulating flexible polymer
circuit board for microfluidic component.
Nanotechnology also features in the development of novel biosensors
integrated with microfluidics at Microinstrumentation Lab (µiL). One new sensor is based on the
modification in light transmission through an array of nanoholes using surface
plasmon resonance (SPR). A surface plasmon is a wave along the interface of a
dielectric and a metal5, with a periodic array of
nanoholes dramatically enhancing certain wavelengths of transmitted light while
Transmission SPR sensors can be employed to detect changes in surface
chemistry, such as the adsorption of a biological species to the metal nanohole
surface, resulting in a shift in wavelength at which surface plasmons excite and
peak of transmission. By integrating the nanohole arrays with microfluidics,
samples can be easily flowed past the sensor7
Figure 2. Top down
photograph of enclosed microchannel with integrated snap-in-place interconnect
structures and gold nanohole array. The inset shows a close-up scanning electron
microscope image of a nanohole array with period = 500
Furthermore, Microinstrumentation Lab (µiL) researchers are trapping large
arrays of individual cells to monitor single cell antibody response. Antibodies
emanating from each cell attach to adjacent SPR sensors, one per cell, resulting
in changes in surface plasmon generation and transmission. This collaboration
between engineers, physicists, chemists, and immunologists employs microfluidics
and nanotechnology to help understand immunological processes through real-time
monitoring of individual cells.
In addition to the SPR nanohole array sensor, nanotechnology and
microfabrication are jointly employed by Microinstrumentation Lab (µiL) researchers for flexible
electroenzymatic sensors for monitoring tear glucose levels (Figure 3)8, which are approximately 1/40 of blood glucose levels but
do not require painful pin prick blood sampling. The sensors are fabricated on
flexible polymer substrates suitable for implantation in contact lenses, with
active electrode surfaces modified with combinations of nanostructured surfaces
and enzyme immobilization of glucose oxidase, which produces an electronic
signal that is proportional to glucose level.
Figure 3. Flexible
gold-on-polymer electroenzymatic glucose
1. J.N. Patel, B. Kaminska, B.L. Gray, B.D. Gates, "A
sacrificial SU-8 mask for direct metallization on PDMS", Journal of
Micromechanics and Microengineering, 19:11, 115014 (10pp), 2009.
2. A. Khosla, B.L. Gray, "Preparation, Characterization, and
Micromoulding of Multi-walled Carbon Nanotube Polydimethylsiloxane Conducting
Nanocomposite Polymer", Materials Letters, 63:13-14, pp. 1203-1206, 2009.
3. S. Jaffer, B.L. Gray, D.G. Sahota, M.H. Sjoerdsma, "Mechanical
assembly and magnetic actuation of polydimethylsiloxane-iron composite
interconnects for microfluidic systems", Proceedings of SPIE, vol. 6886, January
2008, 12 pages.
4. A. Khosla, B. L. Gray, D. B. Leznoff, J.
Herchenroeder, D. Miller, "Fabrication of integrated permanent micromagnets for
microfluidic systems", accepted to SPIE Photonics West, January 2010, San
5. R. Gordon, A.G. Brolo, K.L. Kavanagh, D. Sinton, J.
Pond, "Understanding the extraordinary optical properties of nanohole arrays in
metals," Photons, vol. 2, pp. 15-18, 2004.
6. T.W. Ebbesen,
H.J. Lezec, H.F. Ghaemi, T. Thio, P.A. Wolff, "Extraordinary optical
transmission through sub-wavelength hole arrays," Nature, vol. 391, pp. 667-669,
7. S. M. Westwood, B. L. Gray, S. Grist, K. Huffman, S.
Jaffer, K. L. Kavanagh, "SU-8 Polymer Enclosed Microchannels with Interconnect
and Nanohole Arrays as an Optical Detection Device for Biospecies", IEEE 30th
Annual Engineering in Medicine and Biology Conference, Vancouver, August 2008, 4
8. J. Patel, B. Kaminska, B. L. Gray, B. D. Gates, "SU-8
as a peel-off mask for reliable metallization on PDMS for an electro-enzymatic
glucose sensor", Fifth International Conference on Microtechnologies in Medicine
and Biology, Quebec City, April 2009.
Copyright AZoNano.com, Professor Bonnis Gray (Simon Fraser