Design, fabrication, and measurement of microfluidic devices with integrated carbon nanotube sensors

Jiheng Zhao

Since the concept was first introduced in the early 1990s, lab-on-a-chip microsystems with integrated microfluidics and sensors have been widely used in the sensing field. At the same time, single-walled carbon nanotubes (SWCNTs) based nanosensors have attracted significant attention due to their extraordinary mechanical and electrical properties such as high conductivity, chemical stability, and good mechanical strength. Polymer microfluidic devices have received considerable attention due to their low cost, remarkable biocompatibility, and high flexibility when compared to glass and silicon devices. But the fabrication process of all-polymer microfluidics devices can be complicated and often requires a special group of techniques. In particular, different types of polymers possess different properties in terms of surface chemistry and hydrophilicity, making device assembly a challenging task. Moreover, the effective fabrication of labon-a-chip microsystems with integrated SWCNT-based sensors is still a challenge. In our research, we demonstrate the fabrication of an all-polymer microfluidic device through the investigation of the essential surface treatment methods. We also investigated a novel lab-on-a-chip device with integrated SWCNT nanosensors for glycerol concentration detection, which is an indirect indication of fluid viscosity. The device fabricated with photolithography and soft lithography methods enables real-time, in-channel measurements of the concentration of flowing aqueous glycerol solutions. The experimental results show that our device has a relatively high sensitivity for glycerol solutions. In order to demonstrate the functionality of our microfluidic devices and their potential in other fields, a multi-passage device was developed. In this device, a manifold was designed to create uniform flow in each parallel channel. This new device features a single feed passage of varying diameter, eliminating the excess volume from multiple branch steps. The design was validated with micro-particle image velocimetry (PIV), and the flow rates agreed to the order of the experimental uncertainty. Hence, the new device can provide a uniform flow distribution in a compact package, as is needed in microfluidic sensor applications.

Design, fabrication, and measurement of microfluidic devices with integrated carbon nanotube sensors

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