We report a Micro Throttle Pump (MTP) which has been shown to pump 5 microm diameter polystyrene beads at a concentration of 4.5 x 10(7) beads ml(-1). This new MTP design is constructed in a straightforward manner and actuated by a single piezoelectric (PZT) element. Maximum flow rates at 800 Hz drive frequency of 132 microl min(-1) with water and 108 microl min(-1) with a bead suspension were obtained. Maximum back-pressures of 6 kPa were observed in both cases. The reported MTP employs specific location of distinct internal microfluid structures cast in a single compliant elastomeric substrate to exploit the opposing directions of flexure of regions of a piezoelectric-glass composite bonded to the elastomer. By this novel means, distinct flexural regions, exhibiting compressive and tensile stresses respectively, allow both the pump's integrated input and output throttles and its pump chamber to be actuated concurrently by a single PZT. To support MTP design we also report the characterisation of an individual throttle's resistance as a function of actuator deflection and discuss the underlying mechanism of the throttling effect.

We report a micro throttle pump (MTP) with enhanced throttling resulting from beneficial deformation of its elastomer substrate. In the MTP reported, this has doubled the effective deflection of the piezo electric (PZT) actuator with a consequent five-fold enhancement of throttling ratio. This mode of throttling has been modelled by finite element method and computational fluid dynamic techniques whose predictions agreed well with experimental data from a throttle test structure; providing typical throttling ratios of 8:1 at low pressures. The improved throttles have been incorporated in a prototype, single PZT, MTP, fabricated with double-depth microfluidics, which pumped both water and a suspension of 5 µm polystyrene beads at a maximum flow rate of 630 µl min−1 and a maximum back-pressure of 30 kPa at a pumping frequency of 1.1 kHz. This represents an approximate five-fold enhancement of both performance metrics compared to our previous single PZT device.

We report a dual-micropump structure operated by a single actuator element. The constituent micropumps are a form of micro throttle pump (MTP) comprising a narrow flow channel incorporating two microthrottles. We term this a ‘linear MTP’ (LMTP). The LMTP's narrowness, in conjunction with an elastomeric substrate, allows multiple, independent, LMTPs to be actuated by a single piezoelectric actuator thereby suiting it to parallel microfluidic architectures. Furthermore, LMTP elements can be combined into parallel or series composites yielding increased maximum pumping rates or back pressures, respectively, when compared to a single LMTP element. The LMTP's flow-channel-like, linear pump chamber minimizes the development of recirculatory flows associated with circular pump chambers which, in part, determine their frequency response and hence maximum pumping rates. We have modelled, fabricated and evaluated a dual-LMTP. We report operation in three modes: as two distinct pumps, as a series composite pump, and as a parallel composite pump. Operating at about 1.6 kHz, with both pumps under identical load conditions, each pump yielded maximum pumping rates of about 750 µl min−1 and back pressures of 18 kPa, both with close matching. Configured as a series composite, a 35 kPa back pressure was achieved, and configured as a parallel composite, a maximum pumping rate of 1.4 ml min−1 resulted. Images of 5 µm polystyrene beads flowing within an LMTP confirm minimal recirculatory behaviour consistent with the LMTP's increased operating frequencies compared to circular pump chamber MTPs.

We report a reciprocating microfluidic pump, the Micro Throttle Pump (MTP), constructed in a relatively uncomplicated manner from glass and microstructured poly(dimethylsiloxane)(PDMS). Unconventionally, the MTP employs throttling of fluid flow as distinct from fully-closing valve structures. Accordingly, this technique offers the prospect of solid-phase suspension tolerance. The reported MTP employs piezoelectrically (PZT) actuated deformation of flow constrictions (throttles) fabricated from PDMS at the two ports of a central, PZT actuated pump chamber. By appropriate time-sequencing of the individual PZTs' actuation, pumping can be induced in either direction. PDMS' elasticity further facilitates throttle operation by virtue of allowing significant PZT flexure that is substantially independent of the underlying PDMS microstructure. In contrast, in a rigid substrate such as silicon, deformation is constrained to where underlying microstructured cavities exist and this restricts design options. We describe the construction and performance of a prototype MTP capable of pumping 300 microl min(-1) or alternatively generating a back-pressure of 5.5 kPa. Preliminary modelling of MTP operation is also presented.

We report a self-contained microfluidic alternate flow injection mixer (AFIM) employing piezoelectrically actuated, PDMS seal-valves to control injection. AFIMs employ pulsatile injection of liquids to enhance interface surface generation. By allowing control of pulse-volume proportionality by variation of the duty-cycle of the valve control signals, continuously variable ratio mixing is achieved without external fluid control components. Mixing is discussed in the context of ‘rate of new surface generation’, thus allowing comparison with laminating mixer designs. The prototype mixer employs a simple micromould fabrication technique to minimize reversible elastomer valve-seal adhesion and hence allow correct valve operation. The resulting device has been characterized over a range of mixing ratios.