光热操控双核双重乳液滴核聚并特性

doi:10.11949/0438-1157.20250476

摘要/Abstract

摘要：

双重乳液滴是指液滴内部还包含更小液滴，因其独特的壳核结构而备受关注，常被作为反应单元实现诸多功能。本研究提出利用激光光热效应诱导热毛细流动实现双核双重乳液滴核聚并，并采用CLSVOF方法追踪相界面研究其核聚并特性。结果表明：当激光照射两个内液滴中心时，激光局部热效应会在内外界面诱导形成热毛细流动，共同驱动内液滴相互靠近发生聚并；当光斑半径从20 μm增加至50 μm时，内液滴吸收热量增多，温差增大使热毛细流动更强，聚并发生时间逐步提前；当光斑半径进一步增大，内液滴聚并发生时间又逐步推迟；激光功率越小，内液滴聚并发生时间越晚；内液滴半径越大，由于吸收热量增多及初始界面距离缩短，内液滴越早聚并。

关键词: 双重乳液, 光热操控, 聚并, 微流体学, CFD, 多相流

Abstract:

Double-emulsion droplets are droplets that contain smaller droplets inside which are often used as reaction units to achieve various functions and have attracted much attention due to their unique core-shell structure. In this paper, we propose to use laser photothermal effect to induce thermocapillary flow to achieve core-droplet coalescence of double emulsion droplets. We use couple level set and volume of fluid method (CLSVOF) to track phase interface and study its characteristics of core coalescence. The results show that when the laser irradiates the centers of two internal droplets, the local thermal effect of the laser induces the formation of thermal capillary flow at the internal and external interfaces, which together drive the internal droplets closer to each other for coalescence. When the radius of laser increases from 20 μm to 50 μm, the thermal capillary migration is stronger due to the increase in heat absorbed by the internal droplets, leading the coalescence-begin gradually shortened. As the spot radius increases further, the onset of coalescence gradually delays. Lower laser power leads to later coalescence. The larger the radius of the internal droplet, the earlier the internal droplet coalesces due to the increased absorbed heat and the shorted initial interface distance.

Key words: double-emulsion droplet, photothermal manipulation, coalescence, microfluidics, CFD, multiphase flow

中图分类号:

TQ 050

彭桂荣, 王奕淋, 覃静沂, 王智彬, 莫松平, 陈颖. 光热操控双核双重乳液滴核聚并特性[J]. 化工学报, 2025, 76(11): 5764-5775.

Guirong PENG, Yilin WANG, Jingyi QIN, Zhibin WANG, Songping MO, Ying CHEN. Mechanisms of dual-core-coalescence in double-emulsion droplets via photothermal manipulation[J]. CIESC Journal, 2025, 76(11): 5764-5775.

图/表 12

图1 物理模型

Fig.1 Physical model

表1 水和十六烷的物性参数

Table 1 Physical properties of water and hexadecane

工质	密度/(kg/m³)	比热容/(J/(kg·K))	热导率/(W/(m·K))	黏度/(Pa·s)	表面张力/(N/m)
水	998.2	4996.047-5.29412T+0.00858T²	-0.6028+0.00658T-8.42644×10^-6T²	0.06225-5.09763×10^-4T+1.41113×10^-6T²-1.3137×10^-9T³	0.02-1×10^-4(T-300)
十六烷	773.4	28994.24-244.7219T+0.73241T²-7.17898×10^-4T³	0.18745-1.32437×10^-4T-8.53221×10^-8T²	0.153593-1.22841×10^-3T+3.33586×10^-6T²-3.05677×10^-9T³	0.02-1×10^-4(T-300)

表2 网格独立性验证结果

Table 2 Results of grid independence verification

网格数量/个	上峰值速度偏差/%	计算成本/%
791864	2.90	66.29
967032	2.28	51.86
1213056	0.13	35.05
1432448	—	—

图2 模型验证

Fig.2 Model validation

图3 光热效应驱动双重乳液滴核聚并的动态行为

Fig.3 Dynamic behavior of core-coalescence in a double-emulsion droplet driven by photothermal effect

图4 液滴温度梯度及内液滴迁移速度随时间的变化

Fig.4 Temperature gradient and migration velocity with time

图5 光斑半径的影响

Fig.5 Effect of laser beam radius

图6 光斑半径对温度梯度与迁移速度的影响

Fig.6 Influence of laser beam radius on temperature gradient and migration velocity

图7 加热功率的影响

Fig.7 Effect of heating power

图8 激光功率对温度梯度与迁移速度的影响

Fig.8 Influence of laser power on temperature gradient and migration velocity

图9 右内液滴尺寸的影响

Fig.9 Effect of right internal droplet diameter

图10 右侧内液滴直径对温度梯度与迁移速度的影响

Fig.10 Influence of right internal droplet diameter on temperature gradient and migration velocity

参考文献 35

[1]	Gu C Y, Hu C B, Ma C L, et al. Development and characterization of solid lipid microparticles containing vitamin C for topical and cosmetic use[J]. European Journal of Lipid Science and Technology, 2016, 118(7): 1093-1103.
[2]	陈展珠, 叶锦华, 王智彬, 等. 三维分形集成共轴流通道实现液滴高效生成[J]. 化工学报, 2024, 75(12): 4442-4452.
	Chen Z Z, Ye J H, Wang Z B, et al. Efficient generation of droplets through three-dimensional fractal integrated coaxial flow channels[J]. CIESC Journal, 2024, 75(12): 4442-4452.
[3]	石盼, 颜肖潇, 王行政, 等. 一步法制备生物相容油核微胶囊及其可控释放[J]. 化工学报, 2021, 72(1): 619-627.
	Shi P, Yan X X, Wang X Z, et al. One-step fabrication of biocompatible oil-core microcapsules with controlled release[J]. CIESC Journal, 2021, 72(1): 619-627.
[4]	Kumar A, Kaur R, Kumar V, et al. New insights into water-in-oil-in-water (W/O/W) double emulsions: properties, fabrication, instability mechanism, and food applications[J]. Trends in Food Science & Technology, 2022, 128: 22-37.
[5]	吉笑盈, 郑园, 李晓鹏, 等. 微流控可控制备液滴、颗粒和胶囊及其应用[J]. 化工学报, 2024, 75(4): 1455-1468.
	Ji X Y, Zheng Y, Li X P, et al. Controlled preparation of droplets, particles and capsules by microfluidics and their applications[J]. CIESC Journal, 2024, 75(4): 1455-1468.
[6]	Hanson J A, Chang C B, Graves S M, et al. Nanoscale double emulsions stabilized by single-component block copolypeptides[J]. Nature, 2008, 455(7209): 85-88.
[7]	Pan J H, Chen J P, Wang X J, et al. Pickering emulsion: from controllable fabrication to biomedical application[J]. Interdisciplinary Medicine, 2023, 1(3): e20230014.
[8]	Baroud C N, Robert de Saint Vincent M, Delville J P. An optical toolbox for total control of droplet microfluidics[J]. Lab on a Chip, 2007, 7(8): 1029-1033.
[9]	Mazutis L, Baret J C, Griffiths A D. A fast and efficient microfluidic system for highly selective one-to-one droplet fusion[J]. Lab on a Chip, 2009, 9(18): 2665-2672.
[10]	Sesen M, Alan T, Neild A. Microfluidic on-demand droplet merging using surface acoustic waves[J]. Lab on a Chip, 2014, 14(17): 3325-3333.
[36]	Chen X K, Xia Y, Zhang Z Y, et al. Hydrocarbon degradation by contact with anoxic water microdroplets[J]. Journal of the American Chemical Society, 2023, 145(39): 21538-21545.
[37]	Hsieh W D, Chen R H, Chen C W, et al. Micro-explosion of a water-in-hexadecane compound drop[J]. Journal of the Chinese Institute of Engineers, 2012, 35(5): 579-587.
[38]	Hadland P H, Balasubramaniam R, Wozniak G, et al. Thermocapillary migration of bubbles and drops at moderate to large Marangoni number and moderate Reynolds number in reduced gravity[J]. Experiments in Fluids, 1999, 26(3): 240-248.
[39]	Zhao J F, Zhang L, Li Z D, et al. Topological structure evolvement of flow and temperature fields in deformable drop Marangoni migration in microgravity[J]. International Journal of Heat and Mass Transfer, 2011, 54(21/22): 4655-4663.
[40]	Chen X P, Mandre S, Feng J J. Partial coalescence between a drop and a liquid-liquid interface[J]. Physics of Fluids, 2006, 18(5): 051705.
[41]	Chen X P, Mandre S, Feng J J. An experimental study of the coalescence between a drop and an interface in Newtonian and polymeric liquids[J]. Physics of Fluids, 2006, 18(9): 092103.
[42]	Scheele G F, Leng D E. An experimental study of factors which promote coalescence of two colliding drops suspended in water (Ⅰ)[J]. Chemical Engineering Science, 1971, 26(11): 1867-1879.
[11]	Liu K, Ding H J, Liu J, et al. Shape-controlled production of biodegradable calcium alginate gel microparticles using a novel microfluidic device[J]. Langmuir, 2006, 22(22): 9453-9457.
[12]	Shintaku H, Kuwabara T, Kawano S, et al. Micro cell encapsulation and its hydrogel-beads production using microfluidic device[J]. Microsystem Technologies, 2007, 13(8): 951-958.
[13]	Jia Y K, Ren Y K, Liu W Y, et al. Electrocoalescence of paired droplets encapsulated in double-emulsion drops[J]. Lab on a Chip, 2016, 16(22): 4313-4318.
[14]	Guan X W, Hou L K, Ren Y K, et al. A dual-core double emulsion platform for osmolarity-controlled microreactor triggered by coalescence of encapsulated droplets[J]. Biomicrofluidics, 2016, 10(3): 034111.
[15]	Hou L K, Ren Y K, Jia Y K, et al. Continuously electrotriggered core coalescence of double-emulsion drops for microreactions[J]. ACS Applied Materials & Interfaces, 2017, 9(14): 12282-12289.
[16]	Deng N N, Wang W, Ju X J, et al. Wetting-induced formation of controllable monodisperse multiple emulsions in microfluidics[J]. Lab on a Chip, 2013, 13(20): 4047-4052.
[17]	Bremond N, Thiam A R, Bibette J. Decompressing emulsion droplets favors coalescence[J]. Physical Review Letters, 2008, 100(2): 024501.
[18]	Tao Y, Liu W Y, Ge Z Y, et al. Numerical characterization of inter-core coalescence by AC dielectrophoresis in double-emulsion droplets[J]. Electrophoresis, 2022, 43(21/22): 2141-2155.
[19]	宋粉红, 王伟, 陈奇成, 等. 电场作用下双液滴聚合特性[J]. 化工学报, 2021, 72(S1): 371-381.
	Song F H, Wang W, Chen Q C, et al. Coalescence characteristics of the double droplets under electric field[J]. CIESC Journal, 2021, 72(S1): 371-381.
[20]	Xie C Y, Meng S X, Xue L H, et al. Light and magnetic dual-responsive Pickering emulsion micro-reactors[J]. Langmuir, 2017, 33(49): 14139-14148.
[21]	Feng K, Gao N, Zhang W L, et al. Creation of nonspherical microparticles through osmosis-driven arrested coalescence of microfluidic emulsions[J]. Small, 2020, 16(9): e1903884.
[22]	陈庆国, 宋春辉, 梁雯, 等. 非均匀电场下乳化油中液滴变形动力学行为[J]. 化工学报, 2015, 66(3): 955-964.
	Chen Q G, Song C H, Liang W, et al. Kinetics behavior of water droplet deformation in emulsified oil subjected to non-uniform electric field[J]. CIESC Journal, 2015, 66(3): 955-964.
[23]	Su H S, Wang Z B, Chen Y, et al. Numerical simulation on interface dynamics of core coalescence of double-emulsion droplets[J]. Industrial & Engineering Chemistry Research, 2020, 59(48): 21248-21260.
[24]	Cordero M L, Burnham D R, Baroud C N, et al. Thermocapillary manipulation of droplets using holographic beam shaping: microfluidic pin ball[J]. Applied Physics Letters, 2008, 93(3): 034107.
[25]	Robert de Saint Vincent M, Wunenburger R, Delville J P. Laser switching and sorting for high speed digital microfluidics[J]. Applied Physics Letters, 2008, 92(15): 154105.
[26]	Selva B, Miralles V, Cantat I, et al. Thermocapillary actuation by optimized resistor pattern: bubbles and droplets displacing, switching and trapping[J]. Lab on a Chip, 2010, 10(14): 1835-1840.
[27]	Bezuglyi B A, Ivanova N A. Creation, transportation, and coalescence of liquid drops by means of a light beam[J]. Fluid Dynamics, 2006, 41(2): 278-285.
[28]	Jiang P C, Chen R, Zhu X, et al. Light droplet levitation in relation to interface morphology and liquid property[J]. The Journal of Physical Chemistry Letters, 2022, 13(21): 4762-4767.
[29]	Chen X G, Hou L K, Yin Z Q, et al. NIR light-triggered core-coalescence of double-emulsion drops for micro-reactions[J]. Chemical Engineering Journal, 2023, 454: 140050.
[30]	Wang Z B, Chen R, Zhu X, et al. Control of the droplet generation by an infrared laser[J]. AIP Advances, 2018, 8: 015302.
[31]	Yang Y J, Wang Z B, Chen R, et al. Droplet migration and coalescence in a microchannel induced by the photothermal effect of a focused infrared laser[J]. Industrial & Engineering Chemistry Research, 2021, 60(4): 1912-1925.
[32]	Chen Z Z, Qin J Y, Wang Y L, et al. Diverse manipulations of double-emulsion droplets using photothermal effect of infrared laser[J]. Applied Thermal Engineering, 2025, 266: 125751.
[33]	Albadawi A, Donoghue D B, Robinson A J, et al. On the analysis of bubble growth and detachment at low capillary and Bond numbers using volume of fluid and level set methods[J]. Chemical Engineering Science, 2013, 90: 77-91.
[34]	Li S Z, Chen R, Wang H, et al. Numerical investigation of the moving liquid column coalescing with a droplet in triangular microchannels using CLSVOF method[J]. Science Bulletin, 2015, 60(22): 1911-1926.
[35]	Wang Z B, Li S Z, Chen R, et al. Numerical study on dynamic behaviors of the coalescence between the advancing liquid meniscus and multi-droplets in a microchannel using CLSVOF method[J]. Computers & Fluids, 2018, 170: 341-348.