The pumping lid: investigating multi-material 3D printing for equipment-free, programmable generation of positive and negative pressures for microfluidic applications

Abstract

Equipment-free pumping is a challenging problem and an active area of research in microfluidics, with applications for both laboratory and limited-resource settings. This paper describes the pumping lid method, a strategy to achieve equipment-free pumping by controlled generation of pressure. Pressure was generated using portable, lightweight, and disposable parts that can be integrated with existing microfluidic devices to simplify workflow and eliminate the need for pumping equipment. The development of this method was enabled by multi-material 3D printing, which allows fast prototyping, including composite parts that combine materials with different mechanical properties (e.g. both rigid and elastic materials in the same part). The first type of pumping lid we describe was used to produce predictable positive or negative pressures via controlled compression or expansion of gases. A model was developed to describe the pressures and flow rates generated with this approach and it was validated experimentally. Pressures were pre-programmed by the geometry of the parts and could be tuned further even while the experiment was in progress. Using multiple lids or a composite lid with different inlets enabled several solutions to be pumped independently in a single device. The second type of pumping lid, which relied on vapor-liquid equilibrium to generate pressure, was designed, modeled, and experimentally characterized. The pumping lid method was validated by controlling flow in different types of microfluidic applications, including the production of droplets, control of laminar flow profiles, and loading of SlipChip devices. We believe that applying the pumping lid methodology to existing microfluidic devices will enhance their use as portable diagnostic tools in limited resource settings as well as accelerate adoption of microfluidics in laboratories.

Towards autonomous lab-on-a-chip devices for cell phone biosensing

“…This solution uses 150 µL disposable syringes to inject 25 µL urine into a PDMS detection cell containing the reagents for fluorescence detection using the phone camera interfaced with a reusable instrument (Figure 2d). The use of a syringe is a practical choice in this case, but one can imagine a lid pump (Begolo et al, 2014) operating as a suction device integrated with the rest of the fluidics, which could additionally provide precise volume metering. ULOC finger pumps are simpler (Comina et al, 2015a), but they still have not been demonstrated for suction.…”

“…As an alternative to confined vacuum, the use of finger pumps (Comina et al, 2015a;Begolo et al, 2014;Iwai et al, 2014) could be an option to simplify this kind of extraction elements. The concept described by Begolo et al, 2014, is a 3D printed lid configured as a pump to generate positive and also negative pressure (Figure 2b).…”

“…The concept described by Begolo et al, 2014, is a 3D printed lid configured as a pump to generate positive and also negative pressure (Figure 2b). The pumping lid uses a soft seal in its construction, and although additive manufacturing strongly simplifies fabrication, this combination of materials and resolution is normally restricted to advanced and expensive 3D printers.…”

“…The integration of the separation stage is not only relevant for the purpose of devices for cell phone readout but also to shorten the time between separation and analysis, which is critical to reduce variability (Lauks, 1998) and to ensure plasma proteome consistency (SenYung et al, 2006). Plasma separation in regular microfluidic setups can be achieved through different methods (Yang et al, 2006;VanDenlinder and Groisman, 2006;Haeberle et al, 2006;Fan et al, 2008), but integration into an autonomous disposable device requires the elimination of regular valves and pumps or their conversion to low-cost alternatives (Comina et al, 2015a;Begolo et al, 2014).…”

“…In this case whole blood is propelled using a self-powered evacuated dead-end microchannel (Hosokawa et al, 2004(Hosokawa et al, , 2006, which needs to be preserved in a vacuum pouch previous to operation, although the principle could be adapted to other forms of self-propulsion (Wang et al, 2010;Kokalj et al, 2014;Zimmermann et al, 2007;Gervais and Delamarche, 2009) or finger pumps (Comina et al, 2015a;Begolo et al, 2014). The deep trench type of separation feature is also very compatible with 3D printed LOC devices (Comina et al, 2014a(Comina et al, , 2015b and minimizes the number of components and fabrication steps.…”