Use of electric fields for cell manipulation in a microfluidic environment
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
Lab‐On‐a‐Chip (LOC) or Micro Total Analysis System (μTAS) technology requires precise control of minute amounts of liquid. Moving liquids in small capillaries requires bulky expensive external pumps that defy the purpose of microfabrication. By integrating a micropump into the device, it allows the system to be transportable, reliable, energy efficient and inexpensive. Such a microsystem built on a chip has been designed to study separation by dielectrophoretic chromatography. Nanobeads were successfully separated and used separately to measure fluid velocity and study the electroosmosis effect. Cell or beads of different type can be trapped in this system.
This system encompasses a solid‐state AC electroosmotic pump for the manipulation of liquid‐containing cells or molecules. AC Electroosmosis is the movement of induced charges over polarised electrodes created by a non‐uniform electric field. The charges undergo Coulomb forces and drag the fluid with their motion. This results in bulk flow over the electrodes. This micro pump is used in a LOC by fabricating the pump on two sides of a microfluidic channel.
The transport of material from what can be an analyte to a cell is of critical interest. The described system in the second part of this thesis presents the advantage of having a defined number of droplets, each of which is a lab on chip. The paradigm is the droplet and therefore the vessel that carries the information. Surfaces are then the place of interaction with the vessel which carries the second aspect of this thesis.
Several approaches have been investigated, in particular by enclosing the droplet between two slides in order to increase the change of contact angle under the presence of polarised electrodes. This system is known as EWOD (ElectroWetting On Dielectric). It follows the approach of modified Lippmann laws and the modification of the apparent contact angle and therefore the motion of the droplet. The lid is somewhat a problem and the possibility of using liquid dielectrophoresis to create a multitude of droplets of calibrated volume is an advantage, as it is harder to create fixed‐volume droplets with an open geometry by EWOD due to contact angle hysteresis.