Biomedical Engineering Reference
In-Depth Information
pressure and heat. This approach cannot effectively ensure that the
micro-low around the joint is securely sealed. We often found
iniltration from bonding medium of the microchannel, resulting in
low blockage. The characteristic of UV sensitive solidiied bonding
is that the medium will solidify after being exposed to UV light and
bonding is complete. However, it still suffers from the iniltration
problem mentioned above. The double-sided tape-bonding medium
is used to put the bonding medium between two plastic chips. The
low movement of the bonding material between the two plastic
chips is low, thus allowing the bonding tape to be adhered between
the plastic chips, then heating to the appropriate temperature will
complete the bonding. Although this method does not have the
iniltration problem, it cannot assure that the sides are completely
sealed. So, when the microchannel contacts with a solution,
sometimes it may affect the operation of the biosensor chip.
Unattached bonding medium technique is a traditional high-
temperature fusion bonding technique [11]. It uses a gradual
heating process on the surfaces of two sides. When the thin surface
outer layer has melted, the two chips are pressed together to form
a seal, thus negating the iniltration problem. However, with the
heating temperature close to glass transition temperature, it can
greatly affect the size of the microstructure. This issue prompted
the development of partial heating bonding technique [12]. The
main concept of partial heating is to focus heating on a certain
bonding area, such as the microchannel. Common heating sources
are ultrasound and other high-energy lasers. These bonding
techniques can prevent iniltration and can also solve the problem of
imprecision from overall heating. However, this technique has two
disadvantages: residual stress after bonding, expensive equipment,
and ineficient process.
6.3
Fabrication of Diffraction Gratings
A diffraction grating is an optical component with a regular
pattern whose elements are separated by a distance comparable
to the wavelength of light under study. Due to its ability to
disperse polychromatic light into its constituent monochromatic
components, the diffraction grating has been widely used in
astronomical, biological, chemical, metallurgical, and other analytical
investigations. In bio-medical detection, diffraction gratings have
 
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