Controllable droplet coalescence exhibits unique advantages and intriguing prospect in chemical synthesis and biological engineering.Current researches focusing on the droplets of the same physics are,however,limited in terms of the interaction between different reactants.In this work,the electro-coalescence of heterogeneous paireddroplets is investigated in a microfluidic chip controlled by an AC electric field.The characteristics of merging dynamics are analyzed under different electric conditions and fluid properties,and an on-chip cross-linking reaction is conducted to enable the instantaneous production of hydrogel microspheres.We find that the coalescence of heterogeneous paired-droplets expands the range of start positions and prolongs the merging time compared to homogeneous paired-droplets.The evolution process of interfaces is accelerated with the increasing voltage,which contributes to the mixing of diverse components.Different electrical conductivities lead to distinct internal mechanisms within droplets.The voltage across the droplet is reduced with the increasing conductivity,while the enhanced attraction between free charges plays a complimentary role in interface instability.Lowering the surface tension reduced the required electric conditions for coalescence.Endowed with the non-Newtonian property,the droplet presents a non-linear relationship in the coalescence region,triggering coalescence with filaments at low voltages and showcasing superior performance at high frequencies.Based on above findings,we successfully produce alginate hydrogel microspheres with a wide range of concentrations in high monodispersity,achieving a clean fabrication of pure hydrogel without any additives and no need for subsequent cleaning.These results reveal the electro-hydrodynamics of heterogeneous paireddroplets,promoting the development of droplet coalescence in chemical and material science.
We study the production of light nuclei in the coalescence mechanism of Au-Au collisions at midrapidity at √sNN=3GeV.We derive analytic formulas of the momentum distributions of two bodies,three bodies,and four nucleons coalescing into light nuclei and naturally explain the transverse momentum spectra of the deuteron(d),triton(t),helium-3(3He),and helium-4(4He).We reproduce data on the yield rapidity densities,yield ratios,and averaged transverse momenta of d,t,3He,and 4He and provide the proportions of contributions from different coalescence sources for t,3He,and 4He in their production.We find that besides nucleon coalescence,nucleon+nucleus coalescence and nucleus+nucleus coalescence may play requisite roles in light nucleus production in Au-Au collisions at √sNN=3 GeV.
With the increasing demand of recycling disposal of industrial wastewater,oil-in-water(O/W)emulsion has been paid much attention in recent years owing to its high oil con-tent.However,due to the presence of surfactant and salt,the emulsion was usually stable with complex physicochemical interfacial properties leading to increased processing diffi-culty.Herein,a novel flow-through electrode-based demulsification reactor(FEDR)was well designed for the treatment of saline O/W emulsion.In contrast to 53.7%for electrical demul-sification only and 80.3%for filtration only,the COD removal efficiency increased to 92.8%under FEDR system.Moreover,the pore size of electrode and the applied voltage were two key factors that governed the FEDR demulsification performance.By observing the mor-phology of oil droplets deposited layer after different operation conditions and the behavior of oil droplets at the electrode surface under different voltage conditions,the mechanism was proposed that the oil droplets first accumulated on the surface of flow-through elec-trode by sieving effect,subsequently the gathered oil droplets could further coalesce with the promoting effect of the anode,leading to a high-performing demulsification.This study offers an attractive option of using flow-through electrode to accomplish the oil recovery with simultaneous water purification.
