Single-pulse dynamics and flow rates of inertial micropumps

Abstract

Bubble-driven inertial pumps are a novel method of moving liquids through microchannels. We combine high-speed imaging, computational fluid dynamics (CFD) simulations and an effective one-dimensional model to study the fundamentals of inertial pumping. For the first time, single-pulse transient flow through Ushaped microchannels is imaged over the entire pump cycle with 4-µs temporal resolution. Observations confirm the fundamental N-shape flow profile predicted earlier by theory and simulations. Experimental flow rates are used to calibrate the CFD and one-dimensional models to extract an effective bubble strength. Then the frequency dependence of inertial pumping is studied both experimentally and numerically. The pump efficiency is found to gradually decrease once the successive pulses start to overlap in time.

Microfluidic switchboards with integrated inertial pumps

“…In addition, at sub kHz operating frequencies, flow induced by successive pulses does not overlap in time and linear scaling of flow rates with pump frequency is expected. (When the pulses overlap, pump efficiency per pulse goes down, but not significantly [8].) The linear dependence was verified experimentally as shown in Fig.…”

“…8 and are in good agreement with Eq. (8). We close this section by discussing the sources of variation in matrix parameters a and b observed in different experiments.…”

“…5. Every electrical firing impulse applied to a TIJ resistor creates a high-pressure vapor bubble that generates pulse-like flow through the network [8]. For our channel dimensions, the flow lasts for approximately 100 µs.…”

“…Nonlinear switchboards with interaction between pulses is an important but complex area. The single-pump nonlinearity was studied in [8] and found to be relatively weak. In contrast, interaction between different pumps is not weak and can actually be quite significant.…”

Pulsatory Mixing of Laminar Flow Using Bubble-Driven Micro-Pumps

“…The dynamics of bubble formation are complex. The expansion and collapse of this bubble occurs within 50 µs [10]. It is useful to consider the boiling process first in equilibrium before considering its transient behavior.…”