An all-polymer microfluidic system for protein sensing applications with integrated low-cost pumps, surface modification and sealing

As more and more protein disease markers are identified, protein-compatible Labon- Chip platforms for point-of-care diagnostics are desired and currently under investigation. The development of a microfluidic system for protein detection requires careful attention to the specific properties of proteins. To ensure a high sensitivity, it is of particular importance that the surfaces within the microfluidic system of such a platform provide very low protein adsorption, thus allowing most of the proteins to be delivered to the sensor surface. In addition the platform should pay special attention to temperature control, as proteins and immobilized molecules on the sensor surface are highly temperature sensitive. For this reason an additional assembly requirement is that the bonding of the microfluidics to the sensor should be carried out at low temperatures, and that there are no undue temperature increases present during the fluid actuation. The key requirements on the microfluidic platform can be summarized as follows: · Controlled transport of sample and reagents/buffers to sensor surface · Low protein adsorption at channel walls · Control of channel surface energy (e.g. for capillary flow stops) · Tight channel sealing · Tight and stable bonding to sensor part (usually glass-like surfaces) · No heat during bonding or pumping · Low-cost / upscalable fabrication technologies A fully-integrated injection-moulded thermoplastic microfluidic system complete with active pumps, sealing and controlled surface modification suitable for protein applications has therefore been developed. The injection-moulded microfluidic channel system has been treated by a plasma surface modification. This surface modification exhibits a low protein adsorption and (super) hydrophilic and (super) hydrophobic areas within the channels (e.g. for capillary flow stops). Optimum sealing of the channels is further achieved by the application of special laser-cut lowtemperature adhesive sealing tape. Microfluidic flow control is realized by low-cost, low temperature, one-shot micropumps based on electrochemical gas generation inside a hydrogel.