Fluid mechanics of grab/release and volume scavenging instabilities:

抓取/释放和体积清除不稳定性的流体力学：

• 批准号: 0653831
• 负责人: Paul Steen
• 金额: $ 21万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0653831&HistoricalAwards=false
• 关键词: Fluid; mechanics; grab; release; volume

CBET-0653831P. H. Steen, Cornell University - EndowedSurface tension at a liquid/gas interface is known to be cohesive and liquid capillarity at small scales exerts an attraction between adjacent solids. The super-adhesion exhibited by the palm beetle is capillarity-based. Its ability to grab and release depends on manipulating a large number N of small volumes of liquid held by surface tension. This study of the fluid mechanics of release has a focus on the volume-scavenging instabilities that can occur when two or more capillary surfaces (e.g. droplets) connect, enabling volume exchange. Modeling and computation will provide the scientific basis for the target task -- to experimentally realize a man-made adhesive pad inspired by the beetle -- and to better understand the beetle's remarkable capability. Intellectual merit. The normally weak force of surface tension can be effectively amplified by parallel action. The palm beetle, an insect native to Florida, exhibits extra-ordinary adhesion ('super-adhesion') as a defense mechanism using just this strategy. Its stickiness derives from making contact with 120,000 tiny droplets of oil. Together, these little liquid bridges make a bond that can withstand a force up to 100 times the beetle's body weight. Perhaps, most surprisingly, this bond can be released in less than a second. How does the beetle release itself? Provided volume exchange between liquid bridges is possible, one bridge can scavenge volume from its neighbors. When does this instability occur and, if it does occur, can it ease detachment? Can scavenging be avoided or enhanced in a man-made device? It is proposed to answer these questions. They belong to a study of the stability of a system of N coupled nonlinear liquid components. Statics gives the energy landscape and the dynamics of volume transfer is important when scavenging competes with the detachment time-scale.Broader Impacts. Nature provides a variety of controllable adhesion examples (house-fly, gecko, etc). The beetle is distinguished by its control of pico-liter volumes of liquid oil. Understanding the beetle's mechanism(s) of release is (are) important not only to the naturalist but to the engineer. The feasibility of man-made adhesives, of strength per unit weight comparable to what the beetle exhibits and that can be turned on/off (grab/release) on the order of a second, is addressed by the proposed study. Hence, immediate impact will be on man's capability to build a switchable super-adhesive pad for a breadth of applications (ceiling-hanging robotic devices and so forth). More broadly, it is well-accepted that adhesion between two solids and spreading at a liquid-solid interface are closely related to the issue of friction between moving parts and dissipation in the liquid coating of solids. More efficient coating processes would impact both industrial production and daily human activities. The highest level impact will be on the science base for understanding the stability of systems of N-coupled capillary elements. Finally, an impact through education of students will accrue from the study, as well as outreach to the public. Numerous accounts of nature-inspired technology in the popular press strike a positive chord, as they should.

CBET-0653831 P。H. Steen，Cornell大学-已知液体/气体界面处的表面张力是内聚的，并且小尺度下的液体毛细作用在相邻固体之间施加吸引力。棕榈甲虫表现出的超粘附力是基于毛细管作用的。它的抓取和释放能力取决于操纵大量N小体积液体的表面张力。释放的流体力学的这项研究有一个重点的体积清除不稳定性时，可能会发生两个或多个毛细管表面（如液滴）连接，使体积交换。建模和计算将为目标任务提供科学依据-实验实现受甲虫启发的人造粘合垫-并更好地了解甲虫的非凡能力。智力上的优点。平行作用可以有效地放大通常很弱的表面张力。棕榈甲虫，一种原产于佛罗里达的昆虫，表现出非凡的粘附力（“超级粘附力”）作为一种防御机制，正是使用这种策略。它的粘性来自于与120，000个微小油滴的接触。这些小小的液体桥结合在一起，可以承受高达甲虫体重100倍的力。也许，最令人惊讶的是，这种结合可以在不到一秒的时间内释放。甲虫如何释放自己？如果液体桥之间的体积交换是可能的，则一个桥可以从其相邻的桥吸收体积。这种不稳定性何时发生，如果发生，它能缓解分离吗？在人造装置中，清除能避免或加强吗？建议回答这些问题。他们属于一个系统的N耦合非线性液体成分的稳定性研究。静力学给出了能量景观，当清除与分离时间尺度竞争时，体积转移的动力学很重要。自然界提供了各种可控的粘附实例（家蝇、壁虎等）。这种甲虫的特点是能控制皮升体积的液体油。了解甲虫的释放机制不仅对博物学家而且对工程师都很重要。拟议的研究讨论了人造粘合剂的可行性，这种粘合剂的单位重量强度与甲虫的表现相当，并且可以在一秒钟内打开/关闭（抓取/释放）。因此，直接的影响将是对人类的能力，以建立一个可切换的超粘性垫的广泛应用（天花板悬挂机器人设备等）。更广泛地说，人们普遍认为，两种固体之间的粘附和液-固界面处的铺展与移动部件之间的摩擦和固体的液体涂层中的耗散问题密切相关。更高效的涂层工艺将影响工业生产和日常人类活动。最高级别的影响将是对了解N-耦合毛细管元件系统稳定性的科学基础。最后，通过对学生的教育以及对公众的宣传，研究将产生影响。大众媒体上关于自然启发的技术的大量报道引起了积极的共鸣，这是应该的。