D. Purcell, J. McFall, T. Huang, P. Nath
Los Alamos National Laboratory,
Keywords: microfluidics, micro-valves, lab-on-a-chip
Summary:Operations that can be performed in the laboratory beforehand, such as serial dilution to prepare a reagent or sample, are often left out of the microfluidic device due to the complexity of integration1. We demonstrate a microfluidic serial dilution system that relies on integrated, magnetically-coupled array of valves operated by a single driver unit2. The system is composed of a microfluidic card, a magnetically-coupled driver disc, and a peristaltic pump. Internal magnets, which act as valves within the microfluidic card, are actuated vertically by the magnets within the driver. The driver is designed in such a way that by rotating it to specific positions, specific set of valves can be opened or closed. Fig 1 shows the flow diagram and the channel network used to create a microfluidic platform for automated serial dilution. The table in the Fig 1, explains the different logics that can control the valves. The dilution rate can be programmed by changing the timing of the steps. This method can provides several benefits including, • Automation: The process was automated by using a Raspberry Pi. The automated platform can be programmed to perform serial dilution with any given target concentration, reducing human error and loss associated with pipetting. • Reduced Peripherals: The sequence of mixing for serial dilution can be carried out using a single stepper motor taking up minimal space while also opening the potential for operation outside of laboratory settings. • Versatile integration into Lab on a chip platforms: By controlling the flow rates and timing of the valve switching, it is possible to design serial dilution with any incremental dilution ratio without changing the microfluidic channel dimension. The microfluidic card and the driver disc were fabricated using a laser based micro-patterning and lamination of polymer film/sheet. The disc was rotated and controlled using a stepper motor (Fig 2). This work will present the challenges and potential of the serial dilution platforms for applications in lab on a chip and demonstrate our approach to using an array of magnetically coupled micro-valves to perform fully automated serial dilution.