J. McFall, T. Huang, A. Pawar, P. Nath
Los Alamos National Lab,
Keywords: microfluidics, valve, membrane-free
Summary:Power requirements (e.g. electromagnetic valves), low back-pressure rating (e.g. piezo driven valves), scaled need for peripherals (e.g. pneumatic valves), lack of automation (e.g. screw valves), and manufacturing difficulties (e.g. soft lithography) limit wide-spread practical applications of many valves that are reported in the current literature. In this work, we present a novel valve driver technology which can control multiple valves with a single motor controlled by a low cost, portable computing unit such as the Raspberry Pi. Several prototypes have been built to demonstrate automated execution of complex flow management for mixing, serial dilution, and DNA extraction. The working principle of the microfluidic valves and the valve driver technology are presented in Figure 1. Each valve works by actuating a permanent magnet into a position of either blocking or allowing flow through a connecting chamber between two micro-channels. Actuation of the magnets is carried out by a set of external magnets embedded on a rotatable disc. This approach introduces several new features for controlling flow in microfluidic systems: • No membranes to operate the valves: The valves do not contain a membrane. This can elongate the life of the valve as well as the ability to withstand high breakthrough pressures. The membrane-less design of the valve allows the valve to remain functional for longer, regardless of the position of the valve magnet due to the absence of membrane fatigue. In our application we have been able to achieve pressures as high as 30 psi on the valves without getting any breakthrough. • Controlling multiple valves using a single driver: By placing an array of magnets on the driver disc and rotating them according to predetermined logics, it is possible to open/close multiple valves simultaneously. In addition, using permanent magnets allows for the valves to be indirectly controlled with no power input necessary to maintain their on/off positions. We have demonstrated simultaneous control of as many as six valves using a single driver. • Configurable array of valves to execute pre-programmed logic: The magnets on the driver can be placed according to an intended application. By rotating the discs, different combinations of open/closed valves can be obtained to execute a series of logical processing steps in flow. We have developed a single valve driver that can execute multiple microfluidic operations (Table 1) including arbitrary mixing of three different liquids, serial dilution, and DNA extraction. Figure 2 shows a photograph of the integrated system for DNA extraction. Through demonstration of successful operation of our array-able, membrane-free, microfluidic valves and driver technology, we can envision transformational applications from the standpoint of integration, automation, and deployment.