CAREER: Mechanics-Driven Energy Dissipation in Soft Matter Lubrication

该学院早期职业发展计划(Career)奖支持研究，这些研究将有助于根据另一个表面滑动时它们应该如何表现来设计含水的、柔软的材料表面。水凝胶材料已经被用于软性隐形眼镜和生物医学涂层(例如假肢)，因为它们具有透水性、生物相容性和顺应性。然而，由于它们的水化性质和广泛的调整成分的能力，它们的表面滑移行为还没有明确的设计规则。这一奖项将允许高素质的学生研究滑动的机制，并将他们的发现结合到这些水凝胶表面的更具体的设计规则中。这需要他们从几个学科中吸取教训，包括材料科学、机械工程、表面科学，甚至生物力学。这项工作将允许招聘和鼓励工程学中任职人数不足的群体。国际和平协会将参加为人数不足的K-12学生正在进行的两个夏令营，并将通过从工业界引进女工程师领导基于润滑学的教育活动来扩大这些夏令营的课程。具体的互动将集中于突出行业领袖的个人经历，以鼓励夏令营参与者追求STEM职业生涯。PI还将利用大型本科课程活动，特别是设计经验，让学生接触到成功的本科生和研究生研究。这一基础性成果有望推动科学进步，增进国民健康。在人类中，软骨层在化学和生物功能中既提供坚固的润滑性，又提供机械减震。水合软体表面的能量耗散机理，特别是接触和滑动作用下的能量耗散机理还没有得到解决，因此目前还没有办法设计出支持载荷和控制滑动的假肢装置所需的润滑行为。这项工作考察了占主导地位的理论对滑移下的能量耗散的解释能力，包括流体载荷支撑、粘弹性松弛和流体剪切。机械变形和接触的实验将证明或否定不同机制的特征，如压力依赖于摩擦系数。材料的成分也将有所不同，其结果将被汇编成柔软水化表面的指导设计原则。与这项工作的研究目标相辅相成的是教育目标，即通过与行业合作开展高中外展活动和利用大型本科活动接触研究，增加伊利诺伊州和美国STEM专业人员的多样性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development Program (CAREER) award supports research that will contribute to new knowledge for designing hydrated, soft material surfaces based on how they should perform when another surface slides against them. Hydrogel materials are already used for soft contact lenses and biomedical coatings (for example for prosthetics) because they are water-permeable, biocompatible, and compliant. However, their surface slip behavior does not yet have clear design rules because of their hydrated nature and broad ability to tune the composition. This award will allow for highly-qualified students to examine the mechanisms of slip, and to combine their findings into more concrete design rules for these hydrogel surfaces. This requires them to draw from several disciplines including materials science, mechanical engineering, surface science, and even biomechanics. This work will allow for the recruitment and encouragement of underrepresented groups in engineering. The PI will participate in two ongoing summer camps for underrepresented K-12 students and will enlarge the curricula of these camps by bringing in women engineers from industry to lead educational events based on the science of lubrication. Specific interactions will be focused on highlighting the personal experiences of the industry leaders to encourage the camp participants to pursue STEM careers. The PI will also leverage large undergraduate course activities, in particular design experiences, to expose students to successful undergraduate and graduate research. The fundamental results are anticipated to promote scientific progress and advance the national health. In humans, cartilage layers provide both robust lubrication and mechanical damping, among chemical and biological functions. The mechanics of energy dissipation in hydrated soft surfaces, especially under contact and slip, have not been sorted out, and thus there is no way to currently engineer the lubrication behavior required for prosthetic devices which support load and control slip. This work examines reigning theories as to their ability to account for energy dissipation under slip, including fluid load support, viscoelastic relaxation, and fluid shear. Experiments on mechanical deformation and contact will prove or disprove the hallmarks of different mechanisms, such as the pressure-dependence on friction coefficient. The material composition will also be varied, and the results will be assembled into guiding design principles for soft hydrated surfaces. Complementary to the research goal of this work is the educational goal of increasing the diversity of STEM professionals in Illinois and the U.S by collaborating with industry on high school outreach activities and leveraging large undergraduate course activities for exposure to research.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.