Automatic Single Droplet Generator with Control over Droplet Size and Detachment Frequency

Abstract

This paper presents a quite simple, fully automatized single droplet generator, which can be an alternative for more expensive and complicated microfluidic devices. The simple generation nozzle connected to the pressure cells and cheap peristaltic pumps, synchronized via developed software with simple GUI (graphical user interface) implemented into the Raspberry Pi microcomputer allows precise control over the single droplet diameter and detachment frequency. The generator allows the formation of droplets of quite wide range of diameters without the need of orifice diameter replacements. Free control over time available for adsorption of surface active-substances over the surface of immobilized droplet, before its detachment from the orifice, is an advantage of the developed device.

Stability of Liquid Films Formed by a Single Bubble and Droplet at Liquid/Gas and Liquid/Liquid Interfaces in Bovine Serum Albumin Solutions

“…It consisted of three main parts: (i) a square glass column filled with the tested solution, with the generating nozzle sealed at the bottom; (ii) high-speed camera (SpeedCam Weinberger MacroVis) to monitor the single bubble/droplet motion (velocity); and (iii) a system for either qualitative or quantitative determination of the liquid-film (foam or emulsion) stability (kinetic of drainage) under dynamic conditions (i.e., at the early stage of its existence, after bubble/droplet collision with the interface). A single bubble or droplet was generated at the nozzle orifice using self-elaborated generators, which have been described in detail elsewhere. , For air bubble generation, a thick-walled glass capillary of 0.15 mm inner diameter was used as the generating nozzle. The bubble diameter depended only on the solution surface tension and orifice diameter (1.9 mm), with only small deviations (less than 5%) related to the solution surface tension variations.…”

“…The bubble diameter depended only on the solution surface tension and orifice diameter (1.9 mm), with only small deviations (less than 5%) related to the solution surface tension variations. In the case of the dodecane droplet, the three-way generating nozzle consisted of a glass tube and steel needle with an outer diameter of 0.51 mm, sealed concentrically …”

“…A single bubble or droplet was generated at the nozzle orifice using self-elaborated generators, which have been described in detail elsewhere. 20,21 For air bubble generation, a thick-walled glass capillary of 0.15 mm inner diameter was used as the generating nozzle. The bubble diameter depended only on the solution surface tension and orifice diameter (1.9 mm), with only small deviations (less than 5%) related to the solution surface tension variations.…”

“…In the case of the dodecane droplet, the three-way generating nozzle consisted of a glass tube and steel needle with an outer diameter of 0.51 mm, sealed concentrically. 21 A single droplet of adjustable size was formed at the needle tip owing to the adjusted overpressure in the glass cell filled with the oil phase. The final droplet size depended on the magnitude of the overpressure impulse from the oil cell.…”

Open Hardware for Microfluidics: Exploiting Raspberry Pi Singleboard Computer and Camera Systems for Customisable Laboratory Instrumentation

“…Various camera modules are available from Raspberry Pi (Table 2, Figure 2). The Raspberry Pi Camera Module 2 (GBP 28.50) The Raspberry Pi computer/camera system has been used in conjunction with microfluidics for different biological studies, ranging from colour and fluorescence detection [37][38][39][40]; for direct cellular image detection and microscopy [39,[41][42][43][44][45][46]; for time-lapse imaging [47]; and for droplet control microfluidics [1,[48][49][50][51] (Table 3).…”