Optofluidic lab-on-chip platform for realtime sensing applications

The risk associated with the presence of various pathogen organisms and viruses in public places have increased need for fast, accurate and reliable methods of detection in small concentrations. Conventional equipment and methods for this purpose has several disadvantages, such as long analysis time, large size and heavy weight, high cost of ownership, and it can be hardly reconfigured. Microfluidics with its small devices dimensions and integrated individual fluidic components represents ideal solution for portable lab-on-chip applications. However, widespread continuous-flow microfluidic chips less suitable for multitasking application and various fluids on-chip manipulations. Such continuous-flow microfluidic systems are very difficult to scale (or integrate), because all the chip channels are controlled by a number of input pressure sources making flow at each chip location dependent on the properties of whole microfluidic system. This challenge can be solved either by increasing a number of external chip control units or by using on-chip flow control elements inside microfluidic chip. Additional advantage of active (valves etc.) on-chip elements is an opportunity to create compact portable systems by eliminating bulky external components. In this article, we propose multilayer polydimethylsiloxane (PDMS) technology for integrated flows control based on on-chip micro valves. The key feature of this technology is the intermediate thin layer that allows creating flexible diaphragms between two PDMS microfluidic layers. We manufacture more than hundred various on-chip valves using this technology and perform several thousand open-close circles demonstrating repeatable operation, high stability and nonobservable stress effects of diaphragms. Using six valves PDMS chip designed and fabricated in our center we separate 1 μm and 100 nm diameter polystyrene beads in aqueous solution imitating virus separation. Based on developed technology we fabricate variety of on-chip elements like di/electrophoresis modules, various sensors (patterned metal nanostructures on glass) demonstrating great integration potential for various optofluidic lab-on-chip applications.