流动聚焦及射流不稳定性

司廷; 李广滨; 尹协振

doi:10.6052/1000-0992-16-026

流动聚焦及射流不稳定性

doi: 10.6052/1000-0992-16-026

中国科学技术大学近代力学系, 合肥 230027

详细信息

通讯作者:
司廷, 中国科学技术大学近代力学系副教授. 2000 年考入中国科学技术大学, 2004 年获得学士学位, 2009 年获得流体力学博士学位, 之后从事博士后研究工作, 2012 年引进为中国科学技术大学副教授. 曾于 2012 年及 2014—2016 年到美国俄亥俄州立大学做访问教授. 主要从事实验流体力学、界面流体力学、微纳尺度流动和生物医学工程等方面的基础和应用基础研究, 是中国力学学会流体力学委员会微纳尺度流动专业组成员, 中国光学学会生物医学光子学专业委员会青年委员, 国际期刊 BMC Cancer 分部副编辑. 目前已主持三项国家自然科学基金项目并参与国家自然科学基金创新研究群体项目和国家重大科研仪器研制项目等, 已经获国家专利 7 项, 在国际期刊发表 SCI 论文近 40 篇, 其中发表在流体力学著名期刊 Journal of Fluid Mechanics 和 Physics of Fluids 上的论文共 14 篇.E-mail: tsi@ustc.edu.cn

中图分类号: O358
计量
- 文章访问数: 3792
- HTML全文浏览量: 841
- PDF下载量: 2054
- 被引次数: 0
出版历程
- 收稿日期: 2016-08-23
- 网络出版日期: 2016-11-18
- 刊出日期: 2017-02-24

Flow focusing and jet instability

Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China

More Information

Corresponding author: SI Ting

摘要

摘要: 流动聚焦是一种有效的微细射流产生方法，其原理可以描述为从毛细管流出的流体由另一种高速运动的流体驱动，经小孔聚焦后形成稳定的锥-射流结构，射流因不稳定性破碎成单分散的液滴.自从1998年流动聚焦被提出以来，陆续发展了单轴流动聚焦、电流动聚焦、复合流动聚焦和微流控流动聚焦等毛细流动技术.这些技术稳定、易操作、没有苛刻的环境条件的要求，能够制备单分散性较好的微纳米量级的液滴、颗粒和胶囊，在科学研究和实际应用中具有重要价值.流动聚焦涉及了多尺度、多界面和多场耦合的复杂流体力学问题，其中稳定的锥形是形成稳定射流的先决条件，过程参数是影响射流界面扰动发展的关键因素，而射流不稳定性分析是揭示射流破碎的最主要理论工具.该文回顾了近二十年来不同结构流动聚焦的研究进展，概述这些技术涉及的过程控制、流动模式、尺度律和不稳定性分析等关键力学问题，总结射流不稳定性的研究方法和已取得的成果，最后展望流动聚焦的研究方向和应用前景.
- 流动聚焦 /
- 射流不稳定性 /
- 毛细流动 /
- 界面 /
- 液滴
Abstract: Flow focusing is an effective method to form thin jets. It can be characterized by the formation of a steady cone-jet configuration in the core of a focusing high-speed fluid stream, as the focused fluid is continuously supplied through a capillary needle. The jet issued from the vertex of the cone passes through an orifice, and eventually breaks up into monodisperse droplets due to flow instability. First proposed in 1998, the flow focusing principle has been adopted to develop a series of capillary flow techniques such as single flow focusing, electro-flow focusing, co-flow focusing and microfluidic flow focusing. These techniques are steady, controllable and gentle in producing monodisperse droplets, particles and capsules down to micrometer scale and below. Therefore they have great significance in science, technology and engineering applications. In flow focusing, the formation of the stable cone is the prerequisite condition to form the stable jet; the process parameters influence the perturbations deposited on the jet interface; and the growth of perturbations results in the breakup of the jet. This is a complex problem in fluid mechanics due to its multi-scale, multi-interface and multi-coupling characteristics. Jet instability analysis is the most useful tool for exploring the mechanisms of jet breakup. In this paper, we review the progress of flow focusing with different geometrical structures during recent two decades, and summarize the key mechanics problems of flow focusing including process control, flow modes, scaling laws and instability analyses. The methods and achievements in the study of jet instability are also briefly described. Finally, some future research topics and opportunities for applications are provided.
- flow focusing /
- jet instability /
- capillary flow /
- interface /
- droplet

HTML全文

图 1 同轴射流生成方法的例子. (a)液体射流流出液面(Hertz & Hermanrud 1983), (b)同轴电雾化(Loscertales et al. 2002), (c)同轴流动聚焦(Gañán-Calvo et al. 2007), (d)毛细管微流控流动(Utada et al. 2005)

下载: 全尺寸图片幻灯片

图 2 单轴流动聚焦. (a)核心装置示意图(Martín-Banderas et al. 2005), 1-腔体(提供外部流体), 2-毛细管(输运内部流体), 3-小孔(聚焦流体), (b)流动原理示意图(Gañán-Calvo et al. 2013)

下载: 全尺寸图片幻灯片

图 3 液-气界面结构的单轴流动聚焦实验结果. (a)稳定的锥-射流结构(Gañán-Calvo 1998), (b)冷冻干燥后直径约为5 μm的颗粒扫描电子显微镜图片(Martín-Banderas et al. 2005)

下载: 全尺寸图片幻灯片

图 4 “气-液”界面结构实验结果. (a)稳定的锥形以及小孔外液体裹挟气泡向下游运动(Gordillo et al. 2001a), (b)收集的大量气泡(Gañán-Calvo & Gordillo 2001)

下载: 全尺寸图片幻灯片

图 5 流动聚焦和电雾化相结合形成电流动聚焦(Gañán-Calvo et al. 2006b). (a)电雾化的锥-射流结构, (b)流动聚焦的锥-射流结构, (c)不同条件下电流动聚焦的锥形

下载: 全尺寸图片幻灯片

图 6 同轴流动聚焦. (a)同轴流动聚焦核心装置示意图(Martín-Banderas et al. 2005), 1-外层驱动流体, 2-被驱动流体, 3-同轴锥形, (b)稳定的同轴锥形(Gañán-Calvo et al. 2007), (c)同轴液体射流(Gañán-Calvo 1998), (d)同轴射流破碎图像及制备的多核胶囊微观形貌(Martín-Banderas et al. 2005)

下载: 全尺寸图片幻灯片

图 7 多轴流动聚焦. (a)三轴流动聚焦的核心装置示意图及稳定的锥-射流结构(Si et al. 2015), (b) “一包二”复合电流动聚焦核心装置示意图、稳定的锥-射流结构及制备的多核胶囊微观形貌(Si et al. 2016b)

下载: 全尺寸图片幻灯片

图 8 两相流体的微流控流动聚焦. (a)油-水两相流动的二维微管道结构和不同油-水流量比下的流动模式(Anna et al. 2003), (b)气-液两相流体的二维微管道结构(Hettiarachchi et al. 2007)

下载: 全尺寸图片幻灯片

图 9 三相流体的微流控流动聚焦(Vladisavljevi et al. 2013). (a)二维微管道中的三相流动聚焦结构(Nie et al. 2005), (b)二维微管道中的两级流动聚焦结构(Seo et al. 2007), (c)玻璃微毛细管中的三相流动聚焦结构(Utada et al. 2005), (d)玻璃微毛细管中的两级流动聚焦结构(Chu et al. 2007)

下载: 全尺寸图片幻灯片

图 10 流动聚焦的实验系统. (a)实验平台(Gañán-Calvo et al. 2011), (b)吹气式和吸气式的实验装置(Si et al. 2015), (c)复合针头的设计(Si et al. 2015)

下载: 全尺寸图片幻灯片

图 11 气驱流动聚焦中稳定锥形的界面形态(Si et al. 2015). (a)单轴流动聚焦的液-气界面, (b)同轴流动聚焦的液-液和液-气界面, (c)三轴流动聚焦的液-液(内)、液-液(外)和液-气界面

下载: 全尺寸图片幻灯片

图 12 流动聚焦装置几何参数的影响. (a)单轴流动聚焦中毛细管与小孔不同轴(司廷等2008), (b)单轴流动聚焦中毛细管与小孔间距增大(司廷2009), (c)同轴流动聚焦中毛细管与小孔间距增大(李广滨2016), (d)三轴流动聚焦中毛细管与小孔间距增大(Si et al. 2015)

下载: 全尺寸图片幻灯片

图 13 气驱流动聚焦中外部控制参数的影响. (a)液体流量速度Q_l增大(司廷2009); (b)气体压力差△p_g增大(司廷2009); (c)内部添加染色剂观察回流环的产生, 并与数值模拟结果对比(Gañán-Calvo et al. 2011); (d)稳定锥形的流体边界层及回流环示意图(Gañán-Calvo & Montanero 2009)

下载: 全尺寸图片幻灯片

图 14 核心装置的改进. (a)将毛细管和小孔之间的距离减小形成流动模糊(Gañán-Calvo 2005); (b)将毛细管端口削成尖锐的斜角有利于微量液体聚集(Acero et al. 2013); (c)在毛细管中心插入导流棒抑制回流环的产生(Acero et al. 2012b); (d)将毛细管加工成喷管形状大大减小毛细管口直径, 可用于金属液体聚焦(Vega et al. 2013); (e)将小孔所在平板改成喷管形状有利于形成稳定的流场(Acero et al. 2012a)

下载: 全尺寸图片幻灯片

图 15 电流动聚焦中高分子溶液的射流形态随电场增大的变化情况(陈晓慧等2014)

下载: 全尺寸图片幻灯片

图 16 “液-气”单轴流动聚焦的流动模式及其参数域(Si et al. 2009). (a)流动模式的参数域, (b)六种流动模式的锥-射流图像: (Ⅰ)锥振动模式; (Ⅱ)锥粘连模式; (Ⅲ)螺旋射流模式; (Ⅳ)共存射流模式; (Ⅴ)轴对称射流模式; (Ⅵ)滴模式

下载: 全尺寸图片幻灯片

图 17 电流动聚焦的流动模式及其参数域. (a)电场施加在锥形和射流所在区域(Li et al. 2014), (b)电压和气体压力差变化引起射流的模式转换(Li et al. 2014), (c)锥形稳定和不稳定的转换边界受电压影响(司廷等2011), (d)不同流动模式参数域受电压影响(司廷等2011)

下载: 全尺寸图片幻灯片

图 18 气驱流动聚焦中射流直径的尺度律及实验验证. (a)单轴流动聚焦中射流直径随液体流量速度的变化(Si et al. 2009), (b)单轴流动聚焦中射流直径随气体压力差的变化(Si et al. 2009), (c)三轴流动聚焦中三层液体射流直径随最外层液体流量速度的变化(Si et al. 2015), (d)电流动聚焦中射流直径随气体压力差的变化以及与无电场作用下流动聚焦的尺度律进行对比(Li et al. 2014)

下载: 全尺寸图片幻灯片

图 19 气驱单轴流动聚焦的锥形不稳定性. (a)锥形稳定对应的最小流量速度(Gañán-Calvo & Montanero 2009), (b)在无量纲参数We-Re空间里全局不稳定、局部不稳定和稳定射流三种模式的参数域(Vega et al. 2010)

下载: 全尺寸图片幻灯片

图 20 同轴射流在Rayleigh模式下存在的可能模态(1-内流体, 2-外流体, 3-环境流体). (a) squeezing模态或paravaricose模态, (b) stretching模态或parasinuous模态, (c) transitional模态

下载: 全尺寸图片幻灯片

图 21 液-气射流的简化物理模型. (a)气驱单轴流动聚焦的射流模型(Gordillo et al. 2001b), (b)气驱单轴电流动聚焦的射流模型, 包括有黏和无黏模型(Li et al. 2014)

下载: 全尺寸图片幻灯片

图 22 对单轴流动聚焦的理论预测和实验结果吻合. (a)射流形貌随液体流量速度呈现规律性变化(Si et al. 2009), (b)时间不稳定性理论对界面扰动波长的预测(Si et al. 2009), (c)时空不稳定性理论对滴和射流模式转换的预测(Si et al. 2009), (d)空间不稳定性理论对轴对称和非轴对称射流模式转换的预测(Si et al. 2010)

下载: 全尺寸图片幻灯片

参考文献(156)

[1]	陈晓东, 胡国庆. 2015.微流控器件中的多相流动.力学进展, 45:201503 https://www.researchgate.net/publication/273755498_Multiphase_flow_in_microfluidic_devices Chen X D, Hu G Q. 2015.Multiphase flow in microfluidic devices. Advances in Mechanics, 45:201503. https://www.researchgate.net/publication/273755498_Multiphase_flow_in_microfluidic_devices
[2]	陈晓慧, 张君鹏, 李广滨, 司廷, 尹协振. 2013.电流动聚焦中非牛顿流体射流影响因素的实验研究.实验力学. 28:284-289 http://www.cnki.com.cn/Article/CJFDTOTAL-SYLX201303003.htm Chen X H, Zhang J P, Li G B, Si T, Yin X Z. 2013. Experimental study on the influencing factors of non-Newtonian fluid jets in electro-flow focusing. J. Exp. Mech., 28:284-289. http://www.cnki.com.cn/Article/CJFDTOTAL-SYLX201303003.htm
[3]	陈效鹏. 2003.静电雾化电流体力学研究.[博士论文].合肥:中国科学技术大学.
[4]	陈效鹏, 程久生, 尹协振. 2003.电流体动力学研究进展及应用.科学通报, 48:637-646 doi: 10.1360/03tb9136 Chen X P, Cheng J S, Yin X Z. 2003. Progress and application of electrohydrodynamics. Chinese Science Bulletin, 48:637-646. doi: 10.1360/03tb9136
[5]	李芳. 2007.同轴带电射流的稳定性研究.[博士论文].合肥:中国科学技术大学. http://cdmd.cnki.com.cn/Article/CDMD-10358-2008039430.htm
[6]	李广滨. 2016.复合流动聚焦的实验和理论研究.[博士论文].合肥:中国科学技术大学 http://cdmd.cnki.com.cn/Article/CDMD-10358-1016103170.htm Li G B. 2016.Experimental and theoretical investigation on compound flow focusing.[PhD Thesis]. Hefei:University of Science and Technology of China. http://cdmd.cnki.com.cn/Article/CDMD-10358-1016103170.htm
[7]	李广滨, 司廷, 尹协振. 2012.电场作用下无黏聚焦射流的时间不稳定性研究.力学学报, 44:876-883 http://www.cnki.com.cn/Article/CJFDTOTAL-LXXB201205010.htm Li G B, Si T, Yin X Z. 2012. Temporal instability study of an inviscid focusing jet under an electric field. Chinese J. Theo. Appl. Mech., 44:876-883. http://www.cnki.com.cn/Article/CJFDTOTAL-LXXB201205010.htm
[8]	李战华, 吴健康, 胡国庆, 胡国辉. 2012.微流控芯片中的流体流动.北京:科学出版社 Li Z H, Wu J K, Hu G Q, Hu G H. 2012. Fluid Flow in Microfluidic Chips. Beijing:Science Press.
[9]	林炳承. 2013.微纳流控芯片实验室.北京:科学出版社.
[10]	司廷. 2009.流动聚焦的实验和理论研究.[博士论文]合肥:中国科学技术大学 Si T. Experimental and theoretical investigation on flow focusing.[PhD Thesis]. Hefei:University of Science and Technology of China.
[11]	司廷, 李广滨, 田瑞军, 尹协振. 2011.电场作用下流动聚焦的实验研究.力学学报, 43:1030-1036 http://en.cnki.com.cn/Article_en/CJFDTOTAL-LXXB201106007.htm Si T, Li G B, Tian R J, Yin X Z. 2011. Experimental study of the flow focusing under an electric field.Chinese J. Theor. Appl. Mech., 43:1030-1036. http://en.cnki.com.cn/Article_en/CJFDTOTAL-LXXB201106007.htm
[12]	司廷, 刘志勇, 尹协振. 2008.流动聚焦中锥形和射流直径影响因素的实验研究.实验流体力学, 22:21-26 http://www.cnki.com.cn/Article/CJFDTOTAL-LTLC200801005.htm Si T, Liu Z Y, Yin X Z. 2008. Experimental study of influencing parameters on the cone and the jet diameter in flow focusing. J. Exp. Fluid Mech., 22:21-26. http://www.cnki.com.cn/Article/CJFDTOTAL-LTLC200801005.htm
[13]	司廷, 尹协振. 2011.流动聚焦研究进展及其应用.科学通报, 56:537-546 doi: 10.1360/972010-1639 Si T, Yin X Z. 2011. Progress and application of flow focusing. Chinese Science Bulletin, 56:537-546. doi: 10.1360/972010-1639
[14]	尹协远, 孙德军. 2003.旋涡流动的稳定性.第1版.北京:国防工业出版社 Yin X Y, Sun D J. 2003.Vortex Stability. Beijing:National Defense Industry Press.
[15]	尹协振, 李芳. 2009.电雾化、电纺丝和带电射流稳定性研究.力学与实践, 31:1-7 http://www.cnki.com.cn/Article/CJFDTOTAL-LXYS200901004.htm Yin X Z, Li F. 2009.Electrospraying, electrospinning and instability of electrified jets. Mechanics in Engineering, 31:1-7. http://www.cnki.com.cn/Article/CJFDTOTAL-LXYS200901004.htm
[16]	Acero A J, Ferrera C, Montanero J M, Gañán-Calvo A M. 2012a. Focusing liquid microjets with nozzles.J. Micromech. Microeng., 22:065011. doi: 10.1088/0960-1317/22/6/065011
[17]	Acero A J, Montanero J M, Ferrera C, Herrada M A, Gañán-Calvo A M. 2012b. Enhancement of the stability of the flow focusing technique for low-viscosity liquids. J. Micromech. Microeng., 22:115039. doi: 10.1088/0960-1317/22/11/115039
[18]	Acero A J, Rebollo-Muñoz N, Montanero J M, Gañán-Calvo A M, Vega E J. 2013. A new flow focusing technique to produce very thin jets. J. Micromech. Microeng., 23:065009. doi: 10.1088/0960-1317/23/6/065009
[19]	Agnihotri S A, Mallikarjuna N N, Aminabhavi T M. 2004. Recent advances on chitosan-based micro-and nanoparticles in drug delivery. J. Control. Release, 100:5-28. doi: 10.1016/j.jconrel.2004.08.010
[20]	Anna S L, Bontoux N, Stone H A. 2003. Formation of dispersions using 'flow focusing' in microchannels.Appl. Phys. Lett., 82:364-67. doi: 10.1063/1.1537519
[21]	Artana G, Romat H, Touchard G. 1998. Theoretical analysis of linear stability of electrified jets flowing at high velocity inside a coaxial electrode. J. Electrost., 43:83-100. doi: 10.1016/S0304-3886(97)00163-0
[22]	Artana G, Touchard G, Romat H. 1997. Absolute and convective instabilities in an electrified jet. J.Electrost., 40:33-38. https://www.researchgate.net/publication/222507266_Absolute_and_convective_instabilities_in_an_electrified_jet
[23]	Bailey A G. 1988. Electrostatic Spraying of Liquids. UK:Research Studies Press Ltd.
[24]	Barrero A, Loscertales I G. 2007. Micro-and nanoparticles via capillary flows. Annu. Rev. Fluid Mech., 39:89-106. doi: 10.1146/annurev.fluid.39.050905.110245
[25]	Boeck T, Zaleski S. 2005. Viscous versus inviscid instability of two-phase mixing layers with continuous velocity profile. Phys. Fluids, 17:032106. doi: 10.1063/1.1862234
[26]	Chandrasekhar S. 1961. The capillary instability of a liquid jet. In Hydrodynamic and Hydromagnetic Stability. Oxford:Oxford University Press, 537-542.
[27]	Chang S F, Si T, Zhang S W, Merrick M A, Cohn D E, Xu R X. 2016. Ultrasound mediated destruction of multifunctional microbubbles for image guided delivery of oxygen and drugs. Ultrason. Sonochem., 28:31-38. doi: 10.1016/j.ultsonch.2015.06.024
[28]	Chauhan A, Maldarelli C, Papageorgiou D T, Rumschitzki D S. 2000. Temporal instability of compound threads and jets. J. Fluid Mech., 420:1-25. doi: 10.1017/S0022112000001282
[29]	Chauhan A, Maldarelli C, Rumschitzki D S, and Papageorgiou D T. 1996. Temporal and spatial instability of an inviscid compound jet. Rheol. Acta, 35:567-583. doi: 10.1007/BF00396508
[30]	Chu L Y, Utada A S, Shah R K, Kim J W, Weitz D A. 2007. Controllable monodisperse multiple emulsions.Angew. Chem., 119:9128-9132. doi: 10.1002/(ISSN)1521-3757
[31]	Clanet C, Lasheras J C. 1999. Transition from dripping to jetting. J. Fluid Mech., 383:307-326. doi: 10.1017/S0022112098004066
[32]	Cohen I, Nagel S R. 2002. Scaling at the selective withdrawal transition through a tube suspended above the fluid surface. Phys. Rev. Lett., 88:074501. doi: 10.1103/PhysRevLett.88.074501
[33]	Donnelly R J, Glaberson W. 1966. Experimnets on the capillary instability of a liquid jet. Proc. R. Soc.London Ser. A., 290:547-556. doi: 10.1098/rspa.1966.0069
[34]	Eggers J. 1997. Nonlinear dynamics and breakup of free-surface flows. Rev. Mod. Phys., 69:865-929. doi: 10.1103/RevModPhys.69.865
[35]	Eggers J, Villermaux E. 2008. Physics of liquid jets. Rep. Prog. Phys., 71:036601. doi: 10.1088/0034-4885/71/3/036601
[36]	Elhefnawy A F F, Agoor B M H, Elcoot A E K. 2001. Nonlinear electrohydrodynamic stability of a finitely conducting jet under an axial electric field. Physica A, 297:368-388. doi: 10.1016/S0378-4371(01)00173-X
[37]	Elhefnawy A F F, Moatimid G M, Elcoot A E K. 2004. Nonlinear electrohydrodynamic instability of a finitely conducting cylinder:Effect of interfacial surface charges. Z. angew. Math. Phys., 55:63-91. doi: 10.1007/s00033-003-1115-y
[38]	Eroglu H, Chigier N, Farago Z. 1991. Coaxial atomizer liquid intact lengths. Phys. Fluids A, 3:303-308. doi: 10.1063/1.858139
[39]	Fernández de la Mora J. 2007. The fluid dynamics of Taylor cones. Annu. Rev. Fluid Mech., 39:217-243. doi: 10.1146/annurev.fluid.39.050905.110159
[40]	Freiberg S, Zhu X X. 2004. Polymer microspheres for controlled drug release. Int. J. Pharm., 282:1-18. doi: 10.1016/j.ijpharm.2004.04.013
[41]	Funada T, Joseph D D. 2002. Viscous potential flow analysis of capillary instability. Intl J. Multiphase Flow, 28:1459-1478. doi: 10.1016/S0301-9322(02)00035-6
[42]	Gaonkar A G, Vasisht N, Khare A R, Sobel R. 2014. Microencapsulation in the Food Industry:A Practical Implementation Guide. Amsterdam:Elsevier.
[43]	Graham D Y, Lacey Smith J, Bouvet A A. 1990. What happens to tablets and capsules in the stomach:endoscopic comparison of disintegration and dispersion characteristics of two microencapsulated potassium formulations. J. Pharm. Sci., 79:420-424. doi: 10.1002/jps.2600790512
[44]	Gañán-Calvo A M. 1997. Cone-jet analytical extension of Taylor's electrostatic solution and the asymptotic universal scaling laws in electrospraying. Phys. Rev. Lett., 79:217-220. doi: 10.1103/PhysRevLett.79.217
[45]	Gañán-Calvo A M. 1998. Generation of steady liquid microthreads and micron-sized monodisperse sprays in gas streams. Phys. Rev. Lett., 80:285-288. doi: 10.1103/PhysRevLett.80.285
[46]	Gañán-Calvo A M. 2004. Perfectly monodisperse microbubbling by capillary flow focusing:an alternate physical description and universal scaling. Phys. Rev. E, 69:027301. doi: 10.1103/PhysRevE.69.027301
[47]	Gañán-Calvo A M. 2005. Enhanced liquid atomization:from flow-focusing to flow-blurring. Appl. Phys.Lett., 86:214101. doi: 10.1063/1.1931057
[48]	Gañán-Calvo A M. 2007a. Electro-flow focusing:the high-conductivity low-viscosity limit. Phys. Rev.Lett., 98:134503. doi: 10.1103/PhysRevLett.98.134503
[49]	Gañán-Calvo A M. 2007b. Absolute instability of a viscous hollow jet. Phys. Rev. E, 75:027301. doi: 10.1103/PhysRevE.75.027301
[50]	Gañán-Calvo A M, Barrero A. 1999. A novel pneumatic technique to generate steady capillary microjets.J. Aerosol Sci., 30:117-125. doi: 10.1016/S0021-8502(98)00029-9
[51]	Gañán-Calvo A M, Fernández J M, Oliver A M, Marquez M. 2004. Coarsening of monodisperse wet micro-foams. Appl. Phys. Lett., 84:4989-4991. doi: 10.1063/1.1762992
[52]	Gañán-Calvo A M, Ferrera C, Torregrosa M, Herrada M A, and Marchand M. 2011. Experimental and numerical study of the recirculation flow inside a liquid meniscus focused by air. Microfluid. Nanofluid., 11:65-74. doi: 10.1007/s10404-011-0774-9
[53]	Gañán-Calvo A M, González-Prieto R, Riesco-Chueca P, Herrada M A, Flores-Mosquera M. 2007. Focusing capillary jets close to the continuum limit. Nat. Phys., 3:737-742. doi: 10.1038/nphys710
[54]	Gañán-Calvo A M, Gordillo J M. 2001. Perfectly monodisperse mircobubbling by capillary flow focusing.Phys. Rev. Lett., 87:274501. doi: 10.1103/PhysRevLett.87.274501
[55]	Gañán-Calvo A M, Herrada M A, Garstecki P. 2006a. Bubbling in unbounded coflowing liquids. Phys. Rev.Lett., 96:124504. doi: 10.1103/PhysRevLett.96.124504
[56]	Gañán-Calvo A M, López-Herrera J M, Riesco-Chueca P. 2006b. The combination of electrospray and flow focusing. J. Fluid Mech., 566:421-445. doi: 10.1017/S0022112006002102
[57]	Gañán-Calvo A M, Martín-Banderas L, González-Prieto R, Rodríguez-Gil A, Berdún-Alvarez T, Cebolla Á, Chávez S, Flores-Mosquera M. 2006c. Straightforward production of encoded microbeads by flow focusing:potential applications for biomolecule detection. Int. J. Pharm., 324:19-26. doi: 10.1016/j.ijpharm.2006.05.032
[58]	Gañán-Calvo A M. Montanero J M. 2009. Revision of capillary cone-jet physics:Electrospray and flow focusing. Phys. Rev. E, 79:066305. doi: 10.1103/PhysRevE.79.066305
[59]	Gañán-Calvo A M, Castro-Hernández E, Flores-Mosquera M, Martín-Banderas L. 2015. Massive, generic, and controlled microencapsulation by flow focusing:some physicochemical aspects and new applications.J.Flow Chem., 5:DOI: 10.1556/JFC-D-14-00022
[60]	Gañán-Calvo A M, Montanero J M, Martín-Banderas L, Flores-Mosquera M. 2013. Building functional materials for health care and pharmacy from microfluidic principles and flow focusing. Adv. Drug Deliv.Rev., 65:1447-1469. doi: 10.1016/j.addr.2013.08.003
[61]	Gañán-Calvo A M, Riesco-Chueca P. 2006. Jetting-dripping transition of a liquid jet in a lower viscosity co-flowing immiscible liquid:the minimum flow rate in flow focusing. J. Fluid Mech., 553:75-84. doi: 10.1017/S0022112006009013
[62]	Goedde E F, Yuen M C. 1970. Experiments on liquid jet instability. J. Fluid Mech., 40:495-512. doi: 10.1017/S0022112070000289
[63]	Gordillo J M, Gañán-Calvo A M, Pérez-Saborid M. 2001a. Monodisperse microbubbling:absolute instabil-ities in coflowing gas-liquid jets. Phys. Fluids, 13:3839-3842. doi: 10.1063/1.1416188
[64]	Gordillo J M, Pérez-Saborid M, Gañán-Calvo A M. 2001b. Linear stability of co-flowing liquid-gas jets. J.Fluid Mech., 448:23-51. https://www.researchgate.net/publication/231901466_Linear_stability_of_co-flowing_liquid-gas_jets
[65]	Gu X L, Zhu X, Kong X Z, Tan Y. 2010. Comparisons of simple and complex coacervations for preparation of sprayable insect sex pheromone microcapsules and release control of the encapsulated pheromone molecule.J. Microencapsul., 27:355-364. doi: 10.3109/02652040903221532
[66]	Herrada M A, Gañán-Calvo A M, Guillot P. 2008a. Spatiotemporal instability of a confined capillary jet.Phys. Rev. E, 78:046312. doi: 10.1103/PhysRevE.78.046312
[67]	Herrada M A, Gañán-Calvo A M, Ojeda-Monge A, Bluth B, Riesco-Chueca P. 2008b. Liquid flow focused by a gas:Jetting, dripping, and recirculation. Phys. Rev. E, 78:036323. doi: 10.1103/PhysRevE.78.036323
[68]	Herrada M A, Montanero J M, Ferrera C, Gañán-Calvo A M. 2010. Analysis of the dripping-jetting transition in compound capillary jets. J. Fluid Mech., 649:523-536. doi: 10.1017/S0022112010000443
[69]	Hertz C H, Hermanrud B. 1983. A liquid compound jet.J. Fluid Mech., 131:271-287. doi: 10.1017/S0022112083001329
[70]	Hettiarachchi K, Talu E, Longo M L, Dayton P A, Lee A P. 2007. On-chip generation of microbubbles as a practical technology for manufacturing contrast agents for ultrasonic imaging. Lab Chip, 7:463-468. doi: 10.1039/b701481n
[71]	Holgado M A, Arias J L, Cózar M J, Alvarez-Fuentes J, Gañán-Calvo A M, Fernández-Arévalo M. 2008.Synthesis of lidocaine-loaded PLGA microparticales by flow focusing effects on drug loading and release properties. Int. J. Pharm., 358:27-35. doi: 10.1016/j.ijpharm.2008.02.012
[72]	Huerre P, Monkewitz P A. 1985. Absolute and convective instabilities in free shear flows. J. Fluid Mech., 159:151-168. doi: 10.1017/S0022112085003147
[73]	Huerre P, Monkewitz P A. 1990. Local and global instabilities in spatially developing flows. Annu. Rev.Fluid Mech., 22:473-537. doi: 10.1146/annurev.fl.22.010190.002353
[74]	Kang D J, Lin S P. 1989. Breakup of swirling liquid jets. Int. J. Eng. Fluid Mech., 2:47-62.
[75]	Keller J B, Rubinow S I, Tu Y O. 1973. Spatial instability of a jet. Phys. Fluids, 16:2052-2055. doi: 10.1063/1.1694264
[76]	Kim S H, Weitz D A. 2011. One-step emulsification of multiple concentric shells with capillary microfluidic devices. Angew. Chem. Int. Ed. Engl., 50:8731-8734. doi: 10.1002/anie.201102946
[77]	Kong X Z, Gu X, Zhu X, Zhang Z. 2009. Spreadable dispersion of insect sex pheromone capsules, preparation via complex coacervation and release control of the encapsulated pheromone component molecule. Biomed.Microdevices, 11:275-285. doi: 10.1007/s10544-008-9234-z
[78]	Kumar M. 2000. Nano and microparticles as controlled drug delivery devices. J. Pharm. Pharm. Sci., 3:234-258. http://www.docin.com/p-332134818.html
[79]	Laryea G N, No S Y. 2003. Development of electrostatic pressure-swirl nozzle for agricultural applications.J. Electrostat., 57:129-142. doi: 10.1016/S0304-3886(02)00122-5
[80]	Lasheras J C, Hopfinger E J. 2000. Liquid jet instability and atomization in a coaxial gas stream. Annu.Rev. Fluid Mech., 32:275-308. doi: 10.1146/annurev.fluid.32.1.275
[81]	Law S E. 2001. Agricultural electrostatic spray application:a review of significant research and development during the 20th century. J. Electrostat., 51:25-42. https://www.researchgate.net/publication/223352325_Agricultural_electrostatic_spray_application_A_review_of_significant_research_and_development_during_the_20th_century
[82]	Leib S J, Goldstein M E. 1986a. Convective and absolute instability of a viscous liquid jet. Phys. Fluids, 29:952-954. doi: 10.1063/1.866000
[83]	Leib S J, Goldstein M E. 1986b. The generation of capillary instabilities on a liquid jet. J. Fluid Mech., 168:479-500. doi: 10.1017/S0022112086000472
[84]	Li F, Yin X Y, Yin X Z. 2005. Linear instability analysis of an electrified coaxial jet. Phys. Fluids, 17:077104. doi: 10.1063/1.1996571
[85]	Li F, Yin X Y, Yin X Z. 2006. Linear instability of a coflowing jet under an axial electric field. Phys. Rev.E, 74:036304. doi: 10.1103/PhysRevE.74.036304
[86]	Li F, Yin X Y, Yin X Z. 2008. Instability of a viscous coflowing jet in a radial electric field. J. Fluid Mech., 596:285-311. https://www.researchgate.net/publication/232010693_Instability_of_a_viscous_coflowing_jet_in_a_radial_electric_field
[87]	Li F, Yin X Y, Yin X Z. 2009. Axisymmetric and non-axisymmetric instability of an electrified viscous coaxial jet. J. Fluid Mech., 632:199-225. doi: 10.1017/S0022112009006429
[88]	Li G B, Luo X S, Si T, Xu RX. 2014. Temporal instability of coflowing liquid-gas jets under an electric field.Phys. Fluids, 26:054101. doi: 10.1063/1.4875109
[89]	Lin S P. 2003. Breakup of Liquid Sheets and Jets. Cambridge:Cambridge University Press.
[90]	Lin S P., Chen, J. N. 1998. Role played by the interfacial shear in the instability mechanism of a viscous liquid jet surrounded by a viscous gas in a pipe. J. Fluid Mech., 376:37-51. doi: 10.1017/S0022112098002894
[91]	Lin S P, Ibrahim E A. 1990. Instability of a viscous liquid jet surrounded by a viscous gas in a pipe. J.Fluid Mech., 218:641-658. doi: 10.1017/S002211209000115X
[92]	Lin S P, Lian Z W. 1989. Absolute instability in a gas. Phys. Fluids A, 1:490-493.
[93]	Lin S P, Lian Z W. 1993. Absolute and convective instability of a viscous liquid jet surrounded by a viscous gas in a vertical pipe. Phys. Fluids A, 5:771-773. doi: 10.1063/1.858662
[94]	Lin S P, Reitz R D. 1998. Drop and spray formation from a liquid jet. Annu. Rev. Fluid Mech., 30:85-105. doi: 10.1146/annurev.fluid.30.1.85
[95]	López-Herrera J M, Gañán-Calvo A M, Perez-Saborid M. 1999. One-dimensional simulation of the breakup of capillary jets of conducting liquids. Application to EHD spraying. J. Aerosol Sci., 30:895-912. https://www.researchgate.net/profile/Jose_Lopez-Herrera/publication/241509235_The_breakup_of_a_conducting_charged_jet/links/0a85e5318ba0016fca000000.pdf?inViewer=true&disableCoverPage=true&origin=publication_detail
[96]	López-Herrera J M, Riesco-Chueca P, Gañán-Calvo A M. 2005. Linear stability analysis of axisymmetric perturbations in imperfectly conducting liquid jets. Phys. Fluids, 17:034106. doi: 10.1063/1.1863285
[97]	Loscertales I G, Barrero A, Guerrero I, Cortijo R, Marquez M, Ganan-Calvo A M. 2002. Micro/nano encapsulation via electrified coaxial liquid jets. Science, 295:1695-1698. doi: 10.1126/science.1067595
[98]	Martín-Banderas L, Flores-Mosquera M, Riesco-Chueca P, Rodríguez-Gil A, Cebolla A, Chávez S, Gañán-Ćalvo A M. 2005. Flow Focusing:A Versatile Technology to Produce Size-Controlled and Specific Mor-phology Microparticles. Small, 7:688-692. https://www.researchgate.net/publication/6606265_Flow_Focusing_A_Versatile_Technology_to_Produce_Size-Controlled_and_Specific-Morphology_Microparticles?_sg=rmX4av7HDUTQJxf4Wrssmm_l2nVitG4FFSYk7o0-aYRQnQXL-SohROVTPUBEzUsbsKuinVNyRJEfVxh8jD6-vA
[99]	Martín-Banderas L, Rodríguez-Gil A, Cebolla A, Chávez S, Berdún-Alvarez T, Fernendez-Garcia J M, Flores-Mosquera M, Gañán-Calvo A M. 2006. Towards High-Throughput Production of Uniformly En-coded Microparticles. Adv. Mater., 18:559-564. doi: 10.1002/(ISSN)1521-4095
[100]	Melcher J R. 1963. Field-coupled surface waves. Cambridge MA:MIT.
[101]	Michelson D. 1990. Electrostatic atomization. New York:American Institute of Physics.
[102]	Monkewitz P A. 1990. The role of absolute and convective instability in predicting the behavior of fluid systems. Eur. J. Mech. B/Fluids, 9:395-413.
[103]	Montanero J M, Gañán-Calvo A M. 2008a. Stability of coflowing capillary jets under nonaxisymmetric perturbations. Phys. Rev. E, 77:046301. https://www.researchgate.net/publication/51394443_Stability_of_coflowing_capillary_jets_under_nonaxisymmetric_perturbations
[104]	Montanero J M, Gañán-Calvo A M. 2008b. Viscoelastic effects on the jetting-dripping transition in co-flowing capillary jets. J. Fluid Mech., 610:249-260. https://www.researchgate.net/publication/231884488_Viscoelastic_effects_on_the_jetting-dripping_transition_in_co-flowing_capillary_jets
[105]	Nie Z, Xu S, Seo M, Lewis P C, Kumacheva E. 2005. Polymer particles with various shapes and morphologies produced in continuous microfluidic reactors, J. Am. Chem. Soc., 127:8058-8063. doi: 10.1021/ja042494w
[106]	Ponce-Torres A, Montanero J M, Vega E J, Gañán-Calvo A M. 2016. The production of viscoelastic capillary jets with gaseous flow focusing. J. Non-Newton. Fluid Mech., 229:8-15. doi: 10.1016/j.jnnfm.2016.01.004
[107]	Radev S, Shkadov V. 1985. On a stability of two-layer capillary jet. Theor. Appl. Mech., 16:68-75.
[108]	Radev S, Tchavdarov B. 1988. Linear capillary instability of compound jets. Intl J. Multiphase Flow, 14:67-79. doi: 10.1016/0301-9322(88)90034-1
[109]	Rayleigh L. 1878. On the instability of jets. Proc. London Math. Soc., 10:4-13.
[110]	Rayleigh L. 1879. On the capillary phenomenon of jets. Proc. R. Soc. London, 29:71-97. doi: 10.1098/rspl.1879.0015
[111]	Rayleigh L. 1882. On the equilibrium of liquid conducting masses charged with electricity. Philos. Mag., 14:184-186. doi: 10.1080/14786448208628425
[112]	Rayleigh L. 1892. On the instability of a cylinder of viscous liquid under capillary force. Phil. Mag., 34:145-154. doi: 10.1080/14786449208620301
[113]	Reitz R D, Bracco F V. 1982. Mechanism of atomization of a liquid jet. Phys. Fluids, 25:1730-1742. doi: 10.1063/1.863650
[114]	Reitz R D, Bracco F V. 1986. Mechanisms of breakup of round liquid jets.//Cheremisnoff N ed. The Encyclopedia of Fluid Mechanics, Houston:Gulf. 233-249.
[115]	Reneker D H, Yarin A L. 2008. Electrospinning jets and polymer nanofibers. Polymer, 49:2387-2425. doi: 10.1016/j.polymer.2008.02.002
[116]	Reneker D H, Yarin A L, Fong H. 2000. Bending instability of electrically charged liquid jets of polymer solutions in electrospinning. J. Appl. Phys., 87:4531-4547. doi: 10.1063/1.373532
[117]	Rosell-Llompart J, Gañán-Calvo A M. 2008. Turbulence in pneumatic flow focusing and flow blurring regimes. Phys. Rev. E, 77:036321. doi: 10.1103/PhysRevE.77.036321
[118]	Sanz A, Meseguer J. 1985. One-dimensional linear analysis of the compound jet. J. Fluid Mech., 159:55-68. doi: 10.1017/S0022112085003093
[119]	Saville D A. 1997. Electrohydrodynamics:the Taylor-Melcher leaky dielectric model. Annu. Rev. Fluid Mech., 29:27-64. doi: 10.1146/annurev.fluid.29.1.27
[120]	Sevilla A, Gordillo J M, Martínez-Bazán C. 2002. The effect of the diameter ratio on the absolute and convective instability of free coflowing jets. Phys. Fluids, 14:3028-3038. doi: 10.1063/1.1496511
[121]	Seo M, Paquet C, Nie Z, Xu S, Kumacheva E. 2007. Microfluidic consecutive flowfocusing droplet generators, Soft Matter, 3:986-992. doi: 10.1039/b700687j
[122]	Sheeran P S, Dayton P A. 2012. Phase-Change Contrast Agents for Imaging and Therapy. Current Phar-maceutical Design, 18:2152-2165. doi: 10.2174/138161212800099883
[123]	Shkadov V Y, Sisoev G M. 1996. Instability of a two-layer capillary jet. Intl J. Multiphase Flow, 22:363-377. doi: 10.1016/0301-9322(95)00073-9
[124]	Si T, Feng H X, Luo X S, Xu R X. 2015. Formation of steady compound cone-jet modes and multilayered droplets in a tri-axial capillary flow focusing device. Microfluid. Nanofluid., 18:967-977. doi: 10.1007/s10404-014-1486-8
[125]	Si T, Li F, Yin X Y, Yin X Z. 2009. Modes in flow focusing and instability of coaxial liquid-gas jets. J.Fluid Mech., 629:1-23. doi: 10.1017/S0022112009006211
[126]	Si T, Li F, Yin X Y, Yin X Z. 2010. Spatial instability of co-flowing liquid-gas jets in capillary flow focusing.Phys. Fluids, 22:112105. doi: 10.1063/1.3490066
[127]	Si T, Li G B, Wu Q, Zhu Z Q, Luo X S, Xu R X. 2016a. Optical droplet vaporization of nanoparticle-loaded stimuli-responsive microbubbles. Appl. Phys. Lett., 108:111109. doi: 10.1063/1.4944539
[128]	Si T, Yin C S, Gao P, Li G B, Ding H, He X M, Xie B, Xu R X. 2016b. Steady cone-jet mode in compound-fluidic electro-flow focusing for fabricating multicompartment microcapsules. Appl. Phys. Lett., 108:021601. doi: 10.1063/1.4939632
[129]	Si T, Zhang L L, Li G B, Roberts C J, Yin X Z, Xu R X. 2013. Experimental design and instability analysis of coaxial electrospray process for microencapsulation of drugs and imaging agents. J. Biomed. Opt., 18:075003. doi: 10.1117/1.JBO.18.7.075003
[130]	Sterling A M, Sleicher C A. 1975. The instability of capillary jets. J. Fluid Mech., 68:477-495. doi: 10.1017/S0022112075001772
[131]	Taylor G I. 1940. Generation of ripples by wind blowing over viscous fluids//Batchelor G K ed. The Scientific Papers of G.I. Taylor. Cambridge:Cambridge University Press. 244-254.
[132]	Taylor G I. 1964. Disintegration of water drops in an electric field. Proc. R. Soc. Lond. A, 280:383-397. doi: 10.1098/rspa.1964.0151
[133]	Tomotika S. 1935. On the instability of a cylindrical thread of a viscous liquid surrounded by another viscous fluid. Proc. R. Soc. London Ser. A, 150:322-337. doi: 10.1098/rspa.1935.0104
[134]	Utada A S, Lorenceau E, Link D R, Kaplan P D, Stone H A, Weitz D A. 2005. Monodisperse double emulsions generated from a microcapillary device. Science, 308:537-541. doi: 10.1126/science.1109164
[135]	Vega E J, Gañán-Calvo A M, Montanero J M, Cabezas M G, Herrada M A. 2013. A novel technique for producing metallic microjets and microdrops. Microfluid. Nanofluid., 14:101-111. doi: 10.1007/s10404-012-1027-2
[136]	Vega E J, Montanero J M, Herrada M A, Gañán-Calvo A M. 2010. Global and local instability of flow focusing:The influence of the geometry. Phys. Fluids, 22:064105. doi: 10.1063/1.3450321
[137]	Vladisavljevi G T, Khalid N, Neves M A., Kuroiwa T, Nakajima M, Uemura K, Ichikawa S, Kobayashi I. 2013. Industrial lab-on-a-chip:Design, applications and scale-up for drug discovery and delivery. Adv.Drug Deliv. Rev., 65:1626-1663. doi: 10.1016/j.addr.2013.07.017
[138]	Wang H, Agarwal P, Zhao S, Yu J, Lu X, He X. 2015. A biomimetic hybrid nanoplatform for encapsulation and precisely controlled delivery of theranostic agents. Nature Comm., 6:10081. doi: 10.1038/ncomms10081
[139]	Weber C Z. 1931. Zum Zerfall eines Flussigkeitsstrahles. Math. Mech., 11:136-154.
[140]	Wu P K, Tseng L K, Faeth G M. 1992. Primary breakup in gas/liquid mixing layers for turbulent liquids.At. Sprays, 2:295-318. doi: 10.1615/AtomizSpr.v2.i3
[141]	Xiao J, Yu H, Yang J. 2011. Microencapsulation of sweet orange oil by complex coacervation with soybean protein isolate/gum Arabic. Food Chem., 125:1267-1272. doi: 10.1016/j.foodchem.2010.10.063
[142]	Xu J S, Huang J, Qin R, Hinkle G H, Povoski S P, Martin E W, Xu R X. 2010. Synthesizing and binding dual-mode poly (lactic-co-glycolic acid)(plga) nanobubbles for cancer targeting and imaging. Biomaterials, 31:1716-1722. doi: 10.1016/j.biomaterials.2009.11.052
[143]	Xu R X, Huang J, Xu J S, Sun D, Hinkle G H, Martin E W, Povoski S P. 2009. Fabrication of indocya-nine green encapsulated biodegradable microbubbles for structural and functional imaging of cancer. J.Biomed. Opt., 14:034020. doi: 10.1117/1.3147424
[144]	Yarin A L. 1993. Free Liquid Jets and Films:Hydrodynamic and Rheology. Essex:Longman Science and Technology.
[145]	Yarin A L, Koombhongse, Reneker D H. 2001. Bending instability in electrospinning of nanofibers. J. Appl.Phys., 89:3018-3026. doi: 10.1063/1.1333035
[146]	Yecko P, Zaleski S, Fullana J M. 2002. Viscous modes in two-phase mixing layers. Phys. Fluids, 14:4115-4122. doi: 10.1063/1.1513987
[147]	Yow H N, Routh A F. 2006. Formation of liquid core-polymer shell microcapsules. Soft Matter, 2:940-949. doi: 10.1039/B606965G
[148]	Yuan S, Lei F, Liu Z F, Tong Q P, Si T, Xu R X. 2015. Coaxial electrospray of curcumin-loaded microparticles for sustained drug release. Plos One, 10:e0132609. doi: 10.1371/journal.pone.0132609
[149]	Zakaria K. 2000. Nonlinear instability of a liquid jet in the presence of a uniform electric field. Fluid Dyn.Res., 26:405-420. doi: 10.1016/S0169-5983(99)00021-0
[150]	Zeleny J. 1914. The electrical discharge from liquid points and a hydrostatic method of measuring the electric intensity at their surface. Phys. Rev., 3:69-91. doi: 10.1103/PhysRev.3.69
[151]	Zeleny J. 1915. On the conditions of instability of electrified drops, with applications to the electric discharge from liquid points. Proc. Camb. Phil. Soc., 18:71-83.
[152]	Zhang L L, Huang J W, Si T, Xu R X. 2012. Coaxial electrospray of microparticles and nanoparticles for biomedical applications. Expert Rev. Med. Devices, 9:595-612. doi: 10.1586/erd.12.58
[153]	Zhang L L, Si T, Fischer A, Letson A, Yuan S, Roberts C J, Xu R X. 2015. Coaxial electrospray of ranibizumab-loaded microparticles for sustained release of anti-VEGF therapies. PloS One, 10:e0135608. doi: 10.1371/journal.pone.0135608
[154]	Zhao C. 2013. Multiphase flow microfluidics for the production of single or multiple emulsions for drug delivery. Adv. Drug Deliv. Rev., 65:1420-1446. doi: 10.1016/j.addr.2013.05.009
[155]	Zhu Z Q, Si T, Xu R X. 2015. Microencapsulation of Indocyanine Green for potential applications in image-guided drug delivery. Lab Chip, 15:646-649. doi: 10.1039/C4LC01032A
[156]	Zhu Z Q, Wu Q, Li G B, Han S Y, Si T, Xu R X. 2016. Microfluidic fabrication of stimuli-responsive microdroplets for acoustic and optical droplet vaporizations. J. Mater. Chem. B, 4:2723-2730. doi: 10.1039/C5TB02402A