FINGER-POWERED, PRESSURE-DRIVEN MICROFLUIDIC PUMP K. Iwai, R. D. Sochol, and L. Lin Mechanical Engineering Department, Berkeley Sensor and Actuator Center University of California, Berkeley, USA ABSTRACT Here we present and demonstrate the concept of a versatile ‘human-powered’ fluid pumps as a modular element to provide pressure head for a variety of microfluidic systems. Several distinctive accomplishments have been achieved: (1) human finger as the pumping actuation force; (2) pumping without using any electricity, (3) integrated pump with a passive safety valve and two one-way valves, and (4) successful demonstration in delivering fluids/particles into a microfluidic chip. For the first time, we have demonstrated that measured pressure head by a human finger was between 3-4kPa, which is sufficient to power fluids for various microfluidic applications, such as point-of-care diagnostics. INTRODUCTION People in need of urgent medical diagnostics such as in the battle fields or technological disadvantaged regions often miss the opportunities of being treated promptly due to the requirement of bulky, complex and time-consuming medical instruments. Chip-based microfluidics has the potential to solve some of these problems and make contributions in scientific study such as cellular characterizations [1] as well as in medical applications for quick point-of-care diagnostics [2]. In the state-of-the-art microfluidic devices, one or more bulky and power-hungry syringe pumps are required and it has been a bottleneck in moving chip-scale microfluidics system to practical market places. Therefore, researchers in both academic and industrial labs have been interested in developing low-cost, low-power, and portable micropumps. For example, several groups have previously attempted simple methodologies to pump microfluidics with minimum power consumption such as the application of capillary force on polydimethylsiloxane (PDMS) [3,4] and paper [5,6] as well as the water-powered osmotic actuators and pumps [7,8]. Unfortunately, the magnitude of capillary force is restricted and osmotic actuation is slow such that these methodologies can be applied only to limited microfluidics systems. In this paper, we propose a concept of a versatile ‘human-powered’ fluid pumps as a modular element to provide pressure head for a variety of microfluidic systems. Figure 1 illustrates the basic concept of the finger-powered pump with the demonstration in pumping fluids into a microfluidic chip at the bottom. The finger-powered pump has a deformable chamber which can be activated by a human finger (i.e. pushed by a finger) to infuse solutions out of the pump chamber to the target microfluidic chip. Inlet and outlet are connected with microchannels and various fluidic components. For example, a passive flow rate regulator can be integrated to regulate the flow rate and other passive or active elements can be further integrated into the system. Furthermore, the manufacturing cost is expected to be low as molding and low-cost materials are utilized in the manufacturing process. As such, it is believed that these low-cost, portable and easy-to-operate microfluidic pumps could be promising in practical applications of microfluidic technologies including point-of-care diagnostics. Figure 1. Concept of the human-powered pumping system. By pushing the deformable chamber, mechanical pressure can infuse the solution into the microfluidic chip at the bottom of the pump module. The modular design makes this human-powered pump suitable for a variety of applications. Figure 2. Design detail of the pump. The passive microfluidic diodes direct the liquid solutions from sample storage to outlet with positive pressure, and refill the sample storage from inlet with negative pressure. The passive, movable membrane in the passive fluidic diode can deform under a positive pressure to allow the passage of fluids. Two fluidic diodes are designed as shown to control both the outflow and inlet of fluids. The passive, safety valve has a movable membrane on the top surface to relieve excessive pressure inside the chamber by deformed movable membrane. These movable membranes are not attached to the wall such that the can deform under high fluidic pressure while maintaining reasonable seal by the natural adhesion force to the main substrate.