Phased peristaltic micropumping for continuous sampling and hardcoded droplet generation

Abstract

Droplet microfluidics has recently emerged as a new engineering tool for biochemical analysis of small sample volumes. Droplet generation is most commonly achieved by introducing aqueous and oil phases into a T-junction or a flow focusing channel geometry. This method produces droplets that are sensitive to changes in flow conditions and fluid composition. Here, we present an alternative approach using a simple peristaltic micropump to deliver the aqueous and oil phases in antiphase pulses resulting in a robust "chopping"-like method of droplet generation. This method offers controllable droplet dynamics, with droplet volumes solely determined by the pump design, and is insensitive to liquid properties and flow rates. Importantly, sequences of droplets with controlled composition can be hardcoded into the pump, allowing chemical operations such as titrations and dilutions to be easily achieved. The push-pull pump is compact and can continuously collect samples, generating droplets close to the sampling site and with short stabilisation time. We envisage that this robust droplet generation method is highly suited for continuous in situ sampling and chemical measurement, allowing droplet microfluidics to step out of the lab and into field-deployable applications.

Scalable microfluidic droplet on-demand generator for non-steady operation of droplet-based assays

“…Two innovative aspects of the here introduced two-step formation and release DoD approach are (1) the constrained growth of the droplet to a geometry-controlled (chamber) volume and (2) the decoupling between formation and release. While the use of chambers 46,50 and the decoupling of formation and release based on flow modulation 41,[51][52][53] have been demonstrated before, it is the here introduced combination that makes the on-demand generation insensitive to the pressure upstream and downstream of the generator, enabling the robust scale out.…”

Easily fabricated monolithic fluoropolymer chips for sensitive long-term absorbance measurement in droplet microfluidics

“…Each droplet contained an equal volume of nitrite standard and Griess reagent, which reacted to form a purple coloured diazonium product with an absorbance maximum at $525 nm. The droplets were generated using our previously-reported anti-phase peristaltic pumping approach, 26 whereby oil and aqueous phases are supplied in time-separated pulses. In this way droplet size is determined solely by the volume supplied in each aqueous pulse and allowed us to easily ensure that droplets could be generated of pre-determined sizes (1.6 ml) that could ll every ow cell.…”

“…All uids were pumped using peristaltic pumps built inhouse. 25,26 For initial ow cell testing, droplets were generated in a separate PDMS-based T-junction chip and then owed into the Dyneon THV chip. The droplet generation chip was fabricated using standard replica moulding methods, as previously reported.…”

“…The droplet generation chip was fabricated using standard replica moulding methods, as previously reported. 25 Droplets were generated using the anti-phase peristaltic pumping method, 26 whereby the oil and aqueous phases are delivered in time-separated alternate pulses, meaning droplet size, composition, and generation frequency is mechanically determined by the design of the pump and is independent of oil/aqueous interfacial tension.…”

Micromachined optical flow cell for sensitive measurement of droplets in tubing

“…This paper shows how sensitivities can be improved by upgrading the flow cell from 3D printed cartridge (Hassan et al 2016 ; Nightingale et al 2017 ) to a micromilled cartridge with the limit of detection (LOD) of 0.1 mM as compared to 0.35 mM (3D-printed).…”