A lab-on-a-chip device could cut hospital waiting times.

A lab-on-a-chip device could cut hospital waiting times.

Polymer LED

Lab-on-a-chip devices are well suited to laboratory-based research. However they are not suited to point-of-care applications where portability and cost are important factors. Currently bulky light sources and optical detectors are needed to identify the analytes present even though the chips themselves are small and cheap.

A fully integrated analytical chip that contains an integrated light source and detector could provide powerful point-of-care technology. de Mello predicts that such devices would be capable of carrying out diagnostic tests that are currently restricted to the laboratory. This, he says, would greatly extend the tools available to a doctor and would allow on-the-spot quantitative analysis, eliminating the need for patients to make repeat visits. This would bring forward the start of treatment, lower treatment costs and free up clinician time.

In ongoing work at Imperial College the team use a polymer LED as an integrated excitation source in a microchip based device for capillary electrophoresis. The polymer LED emits light under electrical excitation, and the emission colour is determined by the chemical structure of the polymer used.

The team uses its chip to conduct electrophoretic analysis of a mixture of fluorescein and carboxyfluorescein and compares the results to a mercury lamp excitation source. The observed peaks and the detection limits were broadly similar. It is possible to improve the detection limits for the polymer LED system by using higher driving voltages; this however compromises the lifetime of the polymer LED.

The team intends to direct future research into optimizing the light output while retaining the long lifetimes of the polymer LEDs.

Helen Fletcher