Page 231 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

230 CHAPTER 9 Application of microfluidics in cancer treatment

microchannel cross section and electrode spacing can significantly be
changed if materials are exposed to substantial thermal expansion. The
design of some microvalves and micropumps are based on thermomechanical
actuation. Microfluidic reactors need the ability to set up and control the
temperature of the reactants. Monitoring sensitive changes in heat transfer
is necessary in order to effective heat transfer that is the basic purpose
for microchannel electronics cooling, and some gas sensors. Fluid main
properties such as viscosity are temperature dependent, therefore thermal
properties of microfluidic components are also principle issues. The thermal
properties are important from a production standpoint, even if there are no
temperature-related issues for design functionality. The application of heat to
thermoplastic materials for geometric shaping is so important. For multistep
fabrication processes, the complete sequence of thermal conditions must also
be considered.
3. Electrical properties: For functional purposes such as electrostatic actuation,
electrokinetic pumping, and capacitive sensing, the electrical properties of
materials are important. Some of the most essential properties are resistivity,
relative permittivity (i.e., dielectric constant), and breakdown voltage.
4. Optical properties: Transparency over a wider range of the spectrum beyond
visible light is particularly important for devices based on optical methods
[31,32]. Laser-induced fluorescence is a highly sensitive detection method.
5. Magnetic properties: Ferromagnetic materials are significantly influenced by
magnetic fields that are specially evidenced by force interaction. Nickel, cobalt,
and iron are common metals that exhibit ferromagnetism. Nickel and nickel
alloys are common microfabrication due to established processes.
6. Other physical properties and characteristics: Other physical properties that
should be considered are density, gas permeability, and water absorption.
Hydrophobicity is not a material property because of high dependence on
surface conditions but it is also wildly relater to microfluidics.
9.2.1.5 Considerations
Several functions should be integrated within a compact platform in lab-on-chip
technology that cause to be easily transportable and can deliver rapid data output.
Approximately, surface condition relates to all aspects of microfluidics. Plasma
treatment, chemical surface treatments and laser irradiation are used on this subject.
Usually surface conditions effect significantly on microfluidic functionality [30].
Temperature is one of the functions is required to be controlled from two aspects,
in terms of profile (homogeneous or gradient) and the accessible range, that is pos-
sible with the greatest accuracy. The regulation of temperature is one of the important
parameters manages physical, chemical, and biological applications. Some appli-
cations need tight control of temperature such polymerase chain reaction (PCR),
temperature gradient focusing for electrophoresis (TGF), digital microfluidics, mix-
ing, and protein crystallization [33]. Maintaining the temperature at 37°C to keep
cells alive and controlled temperature cycling for PCRs are principle requirements in