Collaborative Research: Capillary Micro-Switches for Actuation, Photonics and Manufacturing

毛细表面是液/气或液/液界面，其形状由表面张力决定。这种界面通常发生在1000微米或更小的尺度上的液体和气体之间，在这种尺度上，重力的变形可以忽略不计。利用毛细现象已经成为在微观尺度上操纵液体的主要策略。然而，从业者还没有利用这种策略中的毛细管不稳定性。微开关是在亚毫米尺度上的配置，表现出双稳定的行为。正如我们最近所展示的那样，具有非线性响应的简单毛细表面可以组合成“开-关”开关。此外，在圆形开口处形成的毛细表面可以作为具有基本零球差的微透镜。毛细管微透镜的波长范围很广。例如，通过容纳紫外激光器，可以很容易地访问100纳米尺度的特征，因此亚微米读写能力成为可能。另一个应用是非平面表面上的远场光刻。在这里，一组具有可调焦距的可单独寻址镜头是关键。因此，微尺度的毛细管开关可用于聚焦和操纵光（光子学），影响力或运动（驱动）并实现高通量生产（制造）。我们的目标是利用毛细管系统的自然趋势，包括毛细管不稳定性，来操纵它们的广泛应用。具体来说，我们将探索如何调整能量格局，以便由低能量干扰触发从构型a到构型B（以及从构型B到构型a）的变化。在极限情况下，毛细管开关可以设计成几乎可逆的，并且实现将导致节能设备。毛细管系统的触发状态变化可以通过机械（压力）、电（氧化还原表面活性剂）或热（热气动或Marangoni）手段发生。各种刺激将在数百微米和数十微米的尺度上进行检查。

Capillary surfaces are liquid/gas or liquid/liquid interfaces whose shapes are determined by surface tension. Such interfaces generally occur for liquids against gas on scales of 1000 microns or less, scales where deformation by gravity is negligible. Use of capillarity has emerged as a leading strategy for manipulating liquids at the micro-scale. However, practitioners have yet to take advantage of capillary instabilities in such strategies. Micro-switches are configurations on the sub-millimeter scale that exhibit a bi-stable behavior. Simple capillary surfaces with nonlinear response can be combined to make an "on-off" switch, as we have recently demonstrated. Moreover, capillary surfaces formed at circular openings can act as micro-lenses having essentially zero spherical aberration. Capillary micro-lenses admit a wide range of wavelengths. For example, by accommodating uv-lasers, features at 100 nm scale may readily be accessed and hence sub-micron read-write capabilities become possible. Another application is far-field photo-lithography on non-planar surfaces. Here, an array of individually addressable lenses with adjustable focal lengths are the key. Therefore, capillary switches at the micro-scale can be used to focus and manipulate light (photonics), to effect force or motion (actuation) and to implement high through-put production (manufacturing). Our objective is to use the natural tendencies of capillary systems, including capillary instabilities, to manipulate them for a wide range of applications. Specifically, we will explore ways in which the energy landscape can be tuned so that a change from configuration A to B (and back from B to A) can be triggered by low energy disturbances. In the limit, capillary switches can be designed to be nearly reversible and implementation will lead to power-efficient devices.Triggering state changes in capillary systems can occur by mechanical (pressure), electrical (redox surfactants) or thermal (thermo-pneumatic or Marangoni) means. Various stimuli will be examined at a scale of hundreds of microns and at tens of microns.