Microfluidic Droplet dynamics Actuated by Light-Induced Virtual Electrodes - µDrop ALIVE

本计画旨在发展及研究一种光感生电场，以操控微流体微滴于微米大小的通道中。通过引入纯光学形状的电极，将克服微流体平台内的小型化电极的电势的有限可重构性。可重新配置的柔性电极将允许引入自下而上的方法来按需组装液滴组，控制微流体平台内每个液滴的单独轨迹和位置。在微流控通道内通过掺杂铁的钛酸锂晶体的集成施加局部电场，表现出体光伏效应。在用光图案照射时，将在这些晶体的表面附近和微流体液滴装置内产生光致瞬逝电场，从而定制经由光结构与毫微微升和纳升液滴的电相互作用的可能性。软光刻制造协议将用于将该晶体集成到液滴微流体装置中，同时保持通道内液滴流动的润湿性（WP 1）。虚拟电极形状的无限空间控制将通过光成形技术来实现。由光学成形电极提供的高空间灵活性使得该方法对于个体液滴的定制操作是独特的。在可以生成的各种形状中，条形和环形光图案将用于控制Poiffille流（WP 2）中液滴的移动和位置，捕获它们或迫使它们遵循特定的轨迹。系统对液滴执行不同和连续操作的能力将取决于系统的可重构性，并且因此取决于晶体内电荷的重组和系统的微流体部分的时间响应。重构频率将通过特定的实验来测量，旨在分析对虚拟电极系统（WP 3）的时间响应的不同贡献。最后，将利用这种基于光的电相互作用来操纵液滴，以便以自下而上的方法（WP 4）创建液滴集合，例如晶体状结构以及功能性液滴簇。在可以实现的不同配置中，将观察到可定制的2D和1D电势景观中的液滴组件的动态，以及混合操纵将通过液滴内基于纳米和微米颗粒的电封装来解决。

This project aims to develop and study an optically induced electric field to manipulate microfluidic droplets confined in micrometer-sized channels. The limited reconfigurability of the electrical potential by miniaturized electrodes within microfluidic platforms will be overcome by the introduction of purely optically shaped electrodes. Reconfigurable and flexible electrodes will allow the introduction of a bottom-up approach to assemble groups of droplets on demand, controlling the individual trajectory and position of each droplet within a microfluidic platform. A localized electric field will be applied within the microfluidic channels by means of the integration of iron-doped lithium niobate crystals, exhibiting the bulk photovoltaic effect. Upon illumination with light patterns, photoinduced evanescent electric fields will be generated near the surfaces of these crystals and within the microfluidic droplet device, thereby tailoring the potential for electrical interaction with femto- and nanoliter droplets via light structures. A soft lithography fabrication protocol will be used for the integration of this crystal into droplet microfluidic devices, while maintaining the wettability for droplet flow within the channels (WP1). Unlimited spatial control of the virtual electrode shape will be achieved by means of light shaping techniques. The high spatial flexibility provided by the optically shaped electrode makes this approach unique for custom manipulation of individual droplets. Among the wide range of shapes that can be generated, strip- and ring-shaped light patterns will be used to control the movement and position of droplets in Poiseuille flows (WP2), trapping them or forcing them to follow specific trajectories. The ability of the system to perform different and consecutive operations on the droplets will depend on the reconfigurability of the systems and, thus, the reorganization of the charge within the crystal and the temporal response of the microfluidic part of the system. The reconfiguration frequency will be measured by means of specific experiments, aimed at analyzing the different contributions to the temporal response of the virtual electrode systems (WP3). Finally, this light-based electrical interaction will be exploited to manipulate droplets in order to create droplet ensembles, such as crystal-like structures, as well as functional droplet clusters, in a bottom-up approach (WP4). Among the different configurations that can be achieved, the dynamics of droplet assembly in a customizable 2d and 1d electrical potential landscape will be observed, as well as hybrid manipulation will be addressed by nano- and microparticle-based electrical encapsulation within the droplet.