off. At frequencies more or equal to 50 Hz, no pumping action was observed which
was attributed to viscosity of the pumped fluid. In another work reported later [39],
the same group reported an improvised version of micro-pump capable of deliver-
ing 100μL/min at zero back pressure as shown in Fig.2.12.
Peristalsis with soft polymeric membranes have served the purpose of achieving
micro flows although literature has only thoroughly looked at their performance
metrics like flow rate [40], ability to withstand back pressure [41], actuation
mechanism [42, 43] and fabrication strategies. The most widely used discreet
peristaltic strategy that is worth mentioning in this context [44] uses two replicated
and molded layers of Poly-dimethylsiloxane (PDMS) bonded over a hard substrate
with the top layer being used as the actuator layer wherein controlled compressed
air is used to pinch circular chambers inter-connected by thin replicated channels in
the second layer. Some earlier reports on micro-pumps as reported by Kant
et al. [45] involves such architectures as described in the next section.
3.4.1 Micro-pumping System with Peristaltic Motion
Kant et al. have provided an innovative design of peristalsis based micro pump with
an optimized fluid chambers possessing enhanced discharge efficiency per unit
volume of the pumping architecture and reduced reverse flow, very often important
from the standpoint of blood cell sorting assays, within the pumping chamber where
full delivery of fluid containment is critical. Researchers have given a simulation on
COMSOL to optimize the chamber design to evaluate the effect of actuator
membrane interaction. Optimized geometrical profile formulated above was seen
to allow the maximum contact area between fluid containment and actuating
Fig. 2.12 Pumping
sequence of the peristaltic
pump (Reproduced from
Smits [38] with permission
from the Elsevier)
2 Microfluidics Overview 49