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Pumping is an essential component in many microfluidic applications. Developing simple, small-footprint, and flexible pumping methods is of great importance to achieve truly lab-on-a-chip systems. Here, we report a novel acoustic pump based on the atomization effect induced by a vibrating sharp-tip capillary. As the liquid is atomized by the vibrating capillary, negative pressure is generated to drive the movement of fluid without the need to fabricate special microstructures or use special channel materials. We studied the influence of the frequency, input power, internal diameter (ID) of the capillary tip, and liquid viscosity on the pumping flow rate. By adjusting the ID of the capillary from 30 µm to 80 µm and the power input from 1 Vpp to 5 Vpp, a flow rate range of 3 to 520 µL/min can be achieved. We also demonstrated the simultaneous operation of two pumps to generate parallel flow with a tunable flow rate ratio. Finally, the capability of performing complex pumping sequences was demonstrated by performing a bead-based ELISA in a 3D-printed microdevice.
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Capillary rise in sharp corners: not quite universal
We study the capillary rise of viscous liquids into sharp corners formed by two surfaces whose geometry is described by power laws, $$h_i(x) = c_i x^n$$, $i = 1,2$, where $$c_2 > c_1$$ for $$n \geq 1$$. Prior investigations of capillary rise in sharp corners have shown that the meniscus altitude increases with time as $$t^{1/3}$$, a result which is universal, i.e., applies to all corner geometries. The universality of the phenomenon of capillary rise in sharp corners is revisited in this work through the analysis of a partial differential equation for the evolution of a liquid column rising into power-law-shaped corners, which is derived using lubrication theory. Despite the lack of geometric similarity of the liquid column cross-section for $n>1$, there exists a scaling and a similarity transformation that are independent of $$c_i$$ and $$n$$, which gives rise to the universal $$t^{1/3}$$ power-law for capillary rise. However, the prefactor, which corresponds to the tip altitude of the self-similar solution, is a function of $$n$$, and it is shown to be bounded and monotonically decreasing as $$n\to \infty$$. Accordingly, the profile of the interface radius as a function of altitude is also independent of $$c_i$$ and exhibits slight variations with $$n$$. Theoretical results are compared against experimental measurements of the time evolution of the tip altitude and of profiles of the interface radius as a function of altitude.
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- Award ID(s):
- 2127563
- PAR ID:
- 10511253
- Publisher / Repository:
- Journal of Fluid Mechanics (Cambridge University Press)
- Date Published:
- Journal Name:
- Journal of Fluid Mechanics
- Volume:
- 978
- ISSN:
- 0022-1120
- Page Range / eLocation ID:
- A26-1-A26-28
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1017/jfm.2023.1040
