Roller-type squeezing pump with picoliter handling capability

A simple pumping method where a fluid in an integrated elastic microchannel is squeezed out using an external roller has been proposed. Poly(dimethylsiloxane) (PDMS) having a very low Young’s modulus is used to fabricate pumping microchannels, and linearly actuated ball bearings are used to squeeze microchannels and control the pumping volume and rate. This simple construction of the pumping system avoids complicated integration and/or external connections often associated with other pumping schemes. The squeezing pumping can be performed directly on targeted parts within a microchannel network. Squeezing of PDMS microchannels is nearly complete irrespective of the microchannel size, and pumping capacity can be simply changed by using pumping microchannels of different cross-sectional areas. The pumping volume and rate are not affected by the physical properties (pH, ionic strength, viscosity, etc.) of pumping media, and quantitatively controlled by the displacement and its rate of the roller without calibrations. A wide linear range in pumping rate, from 60 to 2400 pl/s has been obtained in both forward and backward pumpings using a microchannel of 200 μm width and 30 μm depth. The picoliter handling capability of the squeezing technique has been demonstrated by performing quantitative segmentations of a fluid into 50 and 100 pl droplets.