Integration of nanosensors into a sealed microchannel in a hybrid lab-on-a-chip device

Commonly used assembly methods for microfluidic devices rely heavily on direct, manual bonding of different components with limited visual aids. The manual operation is likely to cause damage to existing structures, especially to nanoscale sensors on the substrate. Here we report a novel approach to integrate nanosensors into a lab-on-a-chip device with total elimination of operational errors from the manual bonding process. The microfluidic components are composed of an ultraviolet (UV) light-defined, cross-linked SU-8 microchannel and a polydimethylsiloxane (PDMS) top cover. The hybrid microfluidic structure provides a fully sealed microchannel and precisely positioned features. Well-organized single-walled carbon nanotube (SWNT) thin films are deposited and aligned across the electrodes on a silicon substrate with dielectrophoresis. The assembly of SWNTs is carried out in a sealed microchannel which eliminates the potential damage of the nanosensors during the bonding process. The SWNT devices are configured as two-terminal resistor-type sensors with the metal electrodes as the probing pads and the dielectrophoretically captured SWNTs as the sensing elements. To demonstrate the feasibility of this integration approach, an assembled SWNT device is measured as an integrated flow sensor to monitor the flow rate in the microchannel. This lab-on-a-chip device is designed as a platform that can be expanded for more applications. For example, with minimal modifications, the device can be used in chemical sensing, biosensing, and medical research.