A microfluidic device based on an evaporation-driven micropump

Abstract

In this paper we introduce a microfluidic device ultimately to be applied as a wearable sweat sensor. We show proof-of-principle of the microfluidic functions of the device, namely fluid collection and continuous fluid flow pumping. A filter-paper based layer, that eventually will form the interface between the device and the skin, is used to collect the fluid (e.g., sweat) and enter this into the microfluidic device. A controllable evaporation driven pump is used to drive a continuous fluid flow through a microfluidic channel and over a sensing area. The key element of the pump is a micro-porous membrane mounted at the channel outlet, such that a pore array with a regular hexagonal arrangement is realized through which the fluid evaporates, which drives the flow within the channel. The system is completely fabricated on flexible polyethylene terephthalate (PET) foils, which can be the backbone material for flexible electronics applications, such that it is compatible with volume production approaches like Roll-to-Roll technology. The evaporation rate can be controlled by varying the outlet geometry and the temperature. The generated flows are analyzed experimentally using Particle Tracking Velocimetry (PTV). Typical results show that with 1 to 61 pores (diameter = 250 μm, pitch = 500 μm) flow rates of 7.3 × 10-3 to 1.2 × 10-1 μL/min are achieved. When the surface temperature is increased by 9.4 °C, the flow rate is increased by 130 %. The results are theoretically analyzed using an evaporation model that includes an evaporation correction factor. The theoretical and experimental results are in good agreement.Electronic supplementary materialThe online version of this article (doi:10.1007/s10544-015-9948-7) contains supplementary material, which is available to authorized users.

Insight into the Design and Fabrication of a Leaf-Mimicking Micropump

“…Here ∆P represents the material properties (pore size, water potential), whileQ incorporates information about substrate texture and evaporative area (assuming similar environment conditions). [8,11,13,14,16,17,19,[26][27][28] The flow rate obtained from the LMM is comparatively similar to that observed in some other reported passive devices, despite a relatively low suction pressure. However, Figure 5 does not present a complete and fair comparison as some of the examples use device sizes designed for specific applications and not necessarily for assessing the performance limit of their designs (apart from Crawford et al [19]).…”

Advances in passively driven microfluidics and lab-on-chip devices: a comprehensive literature review and patent analysis

“…The hexagonal arrangement at the pore array drove the uid ow and automatically absorbed liquid through a lter paper interface. 169 Mukhopadhyay et al described a leakage-free PMMA fabricated MFD with microchannel bends with the effect of surface wettability on surface-driven capillary ow. This type of microuidic system was utilized in blood cell separation from whole blood.…”

Finger-triggered portable PDMS suction cup for equipment-free microfluidic pumping

“…In this regard, various methods were developed to enable equipment-free microfluidic pumping, such as capillary- [10][11][12], gas- [13], degas- [14,15], pumping lid- [16], and evaporation-driven [17,18] pumping. These approaches offer simplicity of execution by eliminating the need for an off-chip equipment.…”