GOALI: Microscale fundamentals of sweat evaporation

出汗对人体体温调节、热舒适、疾病诊断和卫生产品开发都很重要。然而，人们对水滴如何从我们的汗腺中出现和蒸发知之甚少。这些现象的规模介于生物化学家揭示的驱动汗液产生的分子过程和生理学家进行的宏观汗液速率测量之间。工程师们已经研究了所有这些长度尺度上的蒸发，但仅限于非生物环境。这项工作将使用三种先进的成像技术来提供不同出汗阶段液滴的独特视图。为了确定汗液蒸发的主要物理机制，高分辨率的照片和视频将通过理论建模和人工出汗表面的额外实验进行解释。这些研究成果将潜在地影响从医疗诊断发展到节能建筑设计的各个领域。此外，这项工作将告知工业合作伙伴如何使用暖体假人更真实地模拟出汗。这些设备通常用于服装开发，并优化建筑物和车辆中的气流以提高人体热舒适度。该项目将通过各种联合活动促进学校与行业的伙伴关系，并通过多媒体平台和校园活动与更广泛的公众接触。为了系统地了解各种热流体因素在不同汗液蒸发模式中的作用，项目团队提出了一种双管齐下的跨学科方法，融合了生理学和工程学的观点。首先，将开发一种新方法，将生理学中常规使用的通气胶囊出汗率测量与多模态成像相结合。具体来说，该团队将使用快速宏观摄像，中波红外热成像和光学相干断层扫描。一套非侵入性的方法将被用来同时测量汗液蒸发率和可视化相应的微尺度汗液动力学在三个皮肤部位。该团队将在中性，中等和强烈的热刺激下研究这些过程，这些热刺激将被断言为诱导孔外，滴状和膜状出汗模式。第二，通过实验和建模，探讨各种因素对汗液蒸发的贡献，采用相同的方法，但人工出汗表面逐渐增加的复杂性。这方面的知识将使降阶模型的孔外，逐滴，和filmwise模式的制定。此外，对出汗开始和干燥阶段的成像将加深对生物过程的理解，包括汗液如何通过导管到达皮肤，以及一旦分泌停止，汗液在表面会发生什么。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Sweating is important to human thermoregulation, thermal comfort, illness diagnosis, and hygiene product development. However, little is known about how droplets emerge and evaporate from our sweat glands. The scale of these phenomena is in-between molecular processes that drive sweat generation revealed by biochemists and macroscopic sweat rate measurements performed by physiologists. Engineers have studied evaporation across all these length scales but only in non-biological settings. This work will use three advanced imaging techniques to provide a unique view of droplets during various sweating stages. To identify the main physical mechanisms underlying sweat evaporation, high-resolution photographs and videos will be interpreted with theoretical modeling and additional experimentation with artificial sweating surfaces. These research outcomes will potentially impact diverse fields ranging from medical diagnostic development to energy-efficient building design. In addition, the work will inform the industrial partner how to more realistically mimic sweating using a thermal manikin. These devices are often used in apparel development and to optimize airflow for human thermal comfort in buildings and vehicles. The project will foster the academia-industry partnership with various joint activities and engage with the broader public through multimedia platforms and campus events. To systematically understand the role of various thermofluidic factors in different sweat evaporation modes, the project team proposes a two-pronged transdisciplinary approach that merges physiological and engineering perspectives. First, a new method will be developed to integrate ventilated capsule sweat rate measurements used routinely in physiology with multimodal imaging. Specifically, the team will use fast macro videography, mid-wave infrared thermography, and optical coherence tomography. A suite of non-invasive methods will be used to simultaneously measure sweat evaporation rate and visualize the corresponding microscale sweat dynamics at three skin sites. The team will study these processes under neutral, moderate, and strong thermal stimuli that will be asserted to induce out-of-pore, dropwise, and filmwise sweating modes. Second, the contributions of various factors to sweat evaporation through experimentation and modeling will be explored employing the same method but with artificial sweating surfaces with gradually increasing complexity. This knowledge will enable the formulation of reduced-order models of the out-of-pore, dropwise, and filmwise modes. In addition, imaging sweating onset and drying phases will deepen understanding of biological processes, including how sweat traverses through the duct to the skin and what happens to sweat on the surface once its secretion stops.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.