Design and Fabrication of a Low-cost Wireless Camera Imaging System for Centrifugal Microfluidics

Centrifugal microfluidic devices offer a robust method for low volume fluid handling by combining low-cost instrumentation with highly integrated automation. Crucial to the efficacy of Lab-on-a-Disc (LoaD) device operation is the selection of robust valving technology, the design of on-disc fluidic structures, and accurate control of disc spin-speeds (centrifugal force) during operation. Generally, a fundamental understanding of fluid behaviour at the microlitre level is required to inform the design of on-disc fluidic structures. Therefore, iterative design optimisation of LoaD systems requires the ability to examine and measure the operation of discs during rotation. Scientific cameras, synchronised with a stroboscopic light, are typically employed to visualize on-disc unit operations by capturing synchronized images during rotation. This approach requires a motor/ encoder capable of generating a triggering pulse, a camera and strobe to receive it, and intermediate circuitry to connect the components. Depending on the system decisions taken, such systems can cost from €4,000 upwards. This paper outlines the development of a low-cost centrifugal test-stand with an imaging system using a generic wireless camera to record videos directly to a smartphone device. This imaging system can be fabricated using only 3D printers and a low-cost CNC milling machine from widely available materials for approximately €350. High-fidelity imaging of the entire disc for flow visualisation and the recording of real-time colour intensity measurements are facilitated by this standalone imaging device. A vibration analysis study has been performed to determine the rotational velocity range at which the system can be safely operated. Furthermore, the efficacy of the imaging system has been demonstrated by performing real-time colour intensity measurements of dyed water dilutions.