Linköping doctor invents electroosmotic pump that can be placed in microfluidic chip

Mar 24 2011

Advances in medical diagnostic technology will likely allow individuals to perform preliminary medical diagnoses themselves, in their own home, in the future.

"The idea is to make complex diagnostic processes as simple to perform as modern-day pregnancy tests," says Nathaniel Robinson, who leads the Transport and Separations Group at Linköping University in Sweden

Dr. Robinson and PhD student Per Erlandsson have invented an improved pump, called an electroosmotic pump, which can be placed in a "microfluidic chip".  Such chips, sometimes called "lab-on-a-chip" devices, contain miniaturized versions of the beakers and test tubes found in chemistry laboratories interconnected by tiny pipes.  Rather than using moving parts, the new pump moves fluids in these pipes via an electric current.  The fluids to be pumped can be biological samples such as blood, urine or saliva for medical devices.

"The trick is to generate the ionic current that moves the fluid to be pumped without disturbing the cells, proteins, and other molecules in the sample," according to Dr. Robinson.

To do this, the researchers have employed a type of electronically conducting plastic in the pump's electrodes.  The plastic can be electrochemically oxidized or reduced, acting as a transducer between the ions, the charge carriers in fluids, and electrons, which carry charge in metal wires.  Traditional electroosmotic pumps use metal electrodes and the electrochemical reactions required are performed on the water in the sample itself.  By-products of this electrochemistry included oxygen and hydrogen gas bubbles, and the production of acid or base.  Each of these by-products disturbs the microfluidic device and the fluid sample.

"This is primarily why electroosmotic pumps have not been more widely used in the development of medical devices," says Robinson.

The researchers have shown that the pump can be operated repeatedly for extended periods of time, and can operate at relatively low voltages, so that small, portable diagnostic devices can be driven by batteries.

"Several microfluidics articles describe ways to work around the complications associated with integrated metal-electrodes. Here, the alternative reactions of electrochemically active electrodes give us the chance to remove the core problem, the electrolysis of solvent," according to Per Erlandsson, who constructed the pumps.

The researchers have applied for a patent for the new invention and are currently looking for partners who have a need for such pumps in their lab-on-a-chip devices.  The research is also described in an article appearing in the latest issue of the scientific journal Electrophoresis.

Simple-to-operate medical devices, that will ultimately enable preliminary self-diagnosis via automated testing kits, will likely become an important part of our healthcare system.  Otherwise, we will have a difficult time financing healthcare for an aging population at current or expanded levels of service.  For example, by automating and simplifying screening for diseases, such as cancer, a greater portion of the population can be screened, more cases will be caught early, and hospital resources can focus on treatment of individuals who are truly ill.  This pump is a significant step towards realizing the devices that will make this possible.

Source: http://onlinelibrary.wiley.com/doi/10.1002/elps.201000617/full