Thermocoalescence of microdroplets in a microfluidic chamber

Abstract

Droplet coalescence plays an important role in droplet-based microfluidics. This letter reports the phenomenon of thermocoalescence of two droplets in a chamber with an microheater. An integrated resistive sensor allows the measurement of heating temperature. The merging process was investigated at different flow rates. Experimental results showed that the droplet slows down at increasing temperature and eventually merges with the subsequent droplet. Coalescence occurs at a critical heating temperature. The letter discusses the relationship between droplet velocity, merging temperature and flow rates.

Numerical study of thermocoalescence of microdroplets in a microfluidic chamber

“…The change in viscosity, surface tension, and the effect of surface tension gradient at the fluid interface (Marangoni effects) at elevated temperature are the mechanisms leading to coalescence. Luong et al 10 and Xu et al 11 experimentally reported thermocoalescence of droplets in a heated merging chamber. The experiments showed a dependency of the critical temperature on the flow rate.…”

Ultra-Portable Smartphone Controlled Integrated Digital Microfluidic System in a 3D-Printed Modular Assembly

“…Several microfluidic operations can be performed in the continuous microfluidic systems such as droplet splitting [22], droplet merging [23], droplet dispensing [24,25]. Transport, merging, splitting and dispensing of discrete droplets have been demonstrated successfully on the DMF platform [26][27][28].…”

Industrial lab-on-a-chip: Design, applications and scale-up for drug discovery and delivery

“…The examples of active droplet merging strategies are electro-coalescence 2 [198,[203][204][205], use of pneumatically driven membrane valves [120], optical tweezers [105], and 3 thermo-coalescence [206,207]. The pneumatically driven membrane valve consists of a flat and the last pair of the bypassing branches (Fig.…”

“…Temperature-induced droplet coalescence can be achieved by 10 incorporating heater directly in a merging chamber (Fig. 3.4.1h) [206,207] or in a bypass line…”

“…stream of droplets past off-centered obstruction [190]; (e) Flow of two parallel streams of droplets past off-centered obstruction [190]; (f) Droplet splitting in a flow focusing junction [191]. (b) Circular expansion chamber [192,193]; (c) T-junction [196]; (d) Tapered chamber with diverging walls [199,209]; (e) Trifurcating junction [192,200,201]; (f) two sets of tapering pillars [202]; (g) pneumatically activated membrane valve; (h) expansion chamber with a heating wire [206,207]; (i) Bypass line with a heating element [192]. Emulsification/solvent evaporation [104]; (c) Emulsification in confined geometries [258]; (d) Photolithography [259]; (e) Micromolding [260]; (f) UV-induced polymerization [258]; (g) Nanoprecipitation as a result of mixing of two miscible solvents in laminar flow [261]; (h) Temperature-controlled emulsification/cooling below the phase transition temperature (T 0 -phase transition temperature) [258]; (i) Screening of cells by mixing a suspension of cells with a second aqueous stream containing a fluorogenic substrate in a flow focusing channel [262].…”