SELF-STIMULATION AND SINGLE DROPLET/PARTICLE ENCAPSULATION IN THE CONTROLLED BREAKUP OF LIQUID JETS

液体射流受控破碎中的自刺激和单液滴/颗粒封装

• 批准号: EP/P024173/1
• 负责人: Alfonso Castrejon-Pita
• 金额: $ 12.74万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FP024173%2F1
• 关键词: SELF; STIMULATION; SINGLE; DROPLET; PARTICLE

The breakup of liquid jets into droplets has been the focus of study for more than two centuries. The fast production of microjets and microdroplets has gained additional importance beyond its pure scientific interest motivated by their application in microfluidics devices and in some modern digital technologies, such as 2D and 3D-Printing. Most current studies of this topic aim to improve the control over the position, number and directionality of droplets and their satellites. The objective of this project is two-fold: (i) we will investigate and exploit self-stimulation (resonance) of liquid jets for a better control of the breakup frequency and length; and (ii) once we are able to extract the most unstable (most efficient) frequency we will study the generation of single drops from a continuous liquid jet by means of intermittent pressure pulses. A liquid jet/column will break up into droplets due to the action of surface tension. In continuous inkjet applications the breakup of a jet (or column) of ink is induced and controlled by applying external perturbations in the pressure (or velocity) of the fluid via piezoelectric elements. If the frequency and amplitude of these perturbations are within the so-called 'most unstable modes' range, droplets of uniform size will be obtained. Although these frequencies are roughly predicted by the Rayleigh/Weber equations, in practice this still requires much adjustment and fine tuning; this fine tuning is an empirical process that has to be repeated when different fluids, or inks, are used, which is both limiting and time consuming. We propose to detect and exploit self-stimulated modes in which the system tunes itself to its most unstable frequency by means of feedback. This, by definition, is the most efficient breakup. In this part of the project, mechanisms for self-stimulation will be investigated. The clear advantage of this approach is that the fine tuning is not needed and the breakup frequency can be readily found for a wide range of fluids (within a reasonable operating regime).The second part of the project, the generation of single drops from an otherwise unperturbed jet will be investigated. These single drops could be used for precise deposition, on demand, of small volumes of fluids for a variety of applications (e.g. Inkjet Printing). Moreover, it is envisaged that within these drops single particles (or cells, or other immiscible liquids in emulsion, etc.) can be trapped in real time and selectively delivered to a specific target. These 'particles' may be functional materials, chemical reactants, cells, etc. which are normally dispersed in a carrier fluid on purpose (e.g. fluids with the correct nutrients to sustain life, or functional materials in 'latent' mode) or unintentional and undesired (e.g. solid pollutants). These two overlapping and complementing studies would increase the predictability and reproducibility of the velocity and volume of droplets, and as a consequence these would increase reliability, efficiency and quality of printing technologies.

两个多世纪以来，液体射流分解成液滴一直是研究的焦点。微射流和微液滴的快速生产除了其在微流体设备和一些现代数字技术（如2D和3d打印）中的应用所激发的纯粹科学兴趣之外，还获得了额外的重要性。目前关于这一课题的大部分研究都是为了提高对液滴及其卫星的位置、数量和方向的控制。该项目的目的有两个：(i)我们将研究和利用液体射流的自刺激（共振）来更好地控制破裂频率和长度；（ii）一旦我们能够提取出最不稳定（最有效）的频率，我们将研究通过间歇压力脉冲从连续液体射流中产生单滴的过程。由于表面张力的作用，液体射流/柱会破裂成液滴。在连续喷墨应用中，通过压电元件对流体的压力（或速度）施加外部扰动，可以诱导和控制墨水射流（或柱）的破裂。如果这些扰动的频率和幅度在所谓的“最不稳定模态”范围内，就会得到均匀大小的液滴。虽然这些频率是由瑞利/韦伯方程粗略预测的，但在实践中，这仍然需要大量的调整和微调；这种微调是一个经验过程，当使用不同的流体或油墨时，必须重复，这既有限又耗时。我们建议检测和利用自激模式，其中系统通过反馈将自身调谐到最不稳定的频率。顾名思义，这是最有效的分手方式。在这一部分的项目中，将研究自我刺激的机制。这种方法的明显优点是不需要进行微调，并且可以很容易地找到大范围流体的破裂频率（在合理的操作范围内）。该项目的第二部分，将研究从未受扰动的射流中产生的单滴。这些单滴可用于根据需要精确沉积小体积流体，用于各种应用（例如喷墨打印）。此外，据设想，在这些滴液中，单个颗粒（或细胞，或乳液中的其他不混溶液体等）可以实时捕获并选择性地递送到特定目标。这些“颗粒”可能是功能材料、化学反应物、细胞等，通常是故意分散在载体流体中（例如，含有维持生命所需的正确营养物质的流体，或处于“潜伏”模式的功能材料），也可能是无意的和不需要的（例如，固体污染物）。这两项相互重叠和互补的研究将增加液滴速度和体积的可预测性和可重复性，从而提高印刷技术的可靠性、效率和质量。

项目成果

Formation of radial aligned and uniform nematic liquid crystal droplets via drop-on-demand inkjet printing into a partially-wet polymer layer

• DOI: 10.1016/j.optmat.2018.04.038
• 发表时间: 2018-06-01
• 期刊: OPTICAL MATERIALS
• 影响因子: 3.9
• 作者: Parry, Ellis;Kim, Dong-Jin;Morris, Stephen M.
• 通讯作者: Morris, Stephen M.

Reversal and Inversion of Capillary Jet Breakup at Large Excitation Amplitudes

大激励幅度下毛细管射流破裂的反转和反转

• DOI: 10.1007/s10494-021-00291-w
• 发表时间: 2021
• 期刊: Flow, Turbulence and Combustion
• 作者: Denner F

Evolution of Gaussian wave packets in capillary jets.

毛细管射流中高斯波包的演化。

• DOI: 10.1103/physreve.100.053111
• 发表时间: 2019
• 期刊: Physical review. E
• 作者: García FJ

Controlled cavity collapse: scaling laws of drop formation.

• DOI: 10.1039/c8sm00114f
• 发表时间: 2018-09
• 期刊: Soft matter
• 影响因子: 3.4
• 作者: A. Ismail;A. Gañán-Calvo;J. Castrejón-Pita;M. Herrada;A. A. Castrejón-Pita-A.

A fate-alternating transitional regime in contracting liquid filaments

• DOI: 10.1017/jfm.2018.855
• 发表时间: 2018-12
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: F. Wang;F. P. Contò;N. Naz;J. Castrejón-Pita;A. A. Castrejón-Pita-A.;C. Bailey;W. Wang;J. Feng;Y. Sui