BRIGE: Hagfish Defense Gel and the Rheology Zoo

背景：八目鳗是一种独特的材料，具有显著的性能。当被激怒或攻击时，这种动物会释放少量的生物聚合物/生物丝材料，这些材料在水中展开、组装和膨胀10,000倍。生成的凝胶具有凝聚力，形成了用于防御的堵塞网络。如果可以开发类似的工程材料来模拟这种行为，就可以产生大量的实际应用，如本摘要的更广泛的意义和影响部分所述。项目的技术描述：本提案的研究目标是了解八目鳗防御凝胶的结构-性能机理，并以一种使未来的工作能够设计具有新功能的生物灵感软材料的方式阐明这一理解。我们的方法是全面开发超软材料的流变学测量技术，通过使用惯性弹性振铃技术来突破现有流变仪的实验极限，用于线性和非线性流变学。利用这些技术，我们将测量不同粘蛋白和丝组分质量分数和比例的鳗鱼凝胶复合体系的流变性，包括那些在自然界中未发现的粘蛋白和丝组分。数学建模方法将从瞬变网络理论开始，基于应变硬化的非线性弹性元件，这些元件通过可逆交联链连接，在应力下减弱并提供应力软化。然后，我们将通过与实验、提炼和迭代数学模型进行比较来检验这些结构-特性假设。这里发展的结构-性质关系将不仅适用于鳗鱼凝胶，而且一般包括基于聚合物和/或纤维成分的其他物理凝胶。这将包括角蛋白细丝网络、胶原蛋白网络、粘蛋白凝胶网络和面筋网络，它们都表现出与鳗鱼凝胶相似的非线性流变行为。更广泛的意义和重要性：鳗鱼防御凝胶最初是一小块物质，然后经历戏剧性的体积膨胀，产生一种超稀释、超弹性凝胶，阻止液体通过它。这一行为是当前工程材料所无法比拟的。因此，通过这里的研究发展的理解可能带来可用于应用的材料的根本变化，包括但不限于：(I)石油钻井保障措施，用预存在系统中或根据需要输送到系统的少量材料来堵塞或减缓石油泄漏；(Ii)防御，通过在目的地运送一小包大膨胀的材料来缠绕或堵塞发动机进气口、呼吸进气口或水冷进气口；(Iii)细胞培养，提供纤维线元素的稀疏网络，可为组织支架和3D细胞培养提供独特的结构和长度，补充较小的长度和更致密的胶原纤维支架；(Iv)制造具有解线、补充熔喷、熔纺和电纺工艺的新范式的无纺布材料。鳗鱼凝胶材料是独一无二的，但它的成分引起了人们的普遍兴趣，因为它们是由许多其他软生物材料的积木组成的。扩大代表不足群体对工程学的参与：这项研究将纳入教育和宣传目标，以鼓励代表不足群体在工程学领域的多样性和广泛参与。这将通过开发流变学动物园来实现，这是一个动手策划的流变学有趣材料的图书馆，将作为一个扩展、参与和本科生研究机会的平台。学生们将第一次看到看似简单的材料的非凡行为，了解这种行为在他们的日常生活中是多么重要，并鼓励他们创造性地思考软材料的新工程机会。动物园将是为期六周的暑期项目的一部分，该项目旨在帮助即将入学的学生过渡到大学，其中包括来自代表性不足群体的大量学生。学生们将学习动物园有趣的粘弹性材料，进行简单的测量，并将他们的工作展示给大学外的预科学生，以进一步扩大对工程学的接触和招聘。学生项目将被整合到动物园，为超出本提案资金期限的收集提供一个自我维持的机制。这项研究是通过工程学征集中的扩大参与研究启动补助金资助的，这是工程教育和中心司扩大参与工程计划的一部分。

Background:Hagfish make a unique material with remarkable properties. When provoked or attacked, the animal releases a small volume of biopolymer/biofilament material that unfolds, assembles, and expands in water by a factor of 10,000. The resulting gel is cohesive, forming a clogging network used for defense. If analogous engineering materials could be developed to mimic this behavior, numerous practical applications could result, as noted in the Broader Significance and Impact section of this abstract.Technical description of the project:The research objective of this proposal to understand the structure-property mechanics of hagfish defense gel and to articulate this understanding in a way that will enable future work to design bioinspired soft materials with novel functionality. Our approach is to develop rheological measurement techniques for ultra-soft materials generally, pushing the experimental limits of current rheometers by using techniques such as inertio-elastic ringing for linear and nonlinear rheology. With these techniques we will measure the rheology of various hagfish gel composite systems with varying mass fractions and ratios of mucin and thread components, including those not found in nature. The mathematical modeling approach will start with transient network theory, based on strain-stiffening nonlinear elastic elements connected with reversible crosslinks that weaken under stress and provide stress-softening. We will then test these structure-property hypotheses by comparing with experiment, refining, and iterating the mathematical models. The structure-property relationships developed here will be applicable beyond hagfish gel, and generically include other physical gels based on polymeric and/or fibrous components. This would include keratin filament networks, collagen networks, mucin gel networks, and gluten networks, which have all displayed a similar nonlinear rheological behavior to that observed with the hagfish gel. Broader Significance and Importance:Hagfish defense gel starts as a small volume of material which then undergoes dramatic volumetric expansion, producing an ultra-dilute, super-elastic gel that blocks the flow of liquid through it. This behavior is unmatched by current engineering materials. The understanding developed by the research here could therefore bring about radical changes in materials available for applications including but not limited to (i) Oil-drilling safeguards, to plug or slow oil leaks with a small amount of material that is pre-deposited in the system or delivered to the system as needed; (ii) Defense, to tangle or clog engine intakes, respiratory air intakes, or water-cooling intakes by delivering a small packet of material with big expansion at destination; (iii) Cell cultures, to provide a sparse network of fibrous thread elements which may offer a unique architecture and lengthscale for tissue scaffolds and 3D cell cultures, complementing smaller lengthscale and denser collagen fiber scaffolds; (iv) Manufacturing non-woven materials with new paradigms of unraveling threads, complementing melt blowing, melt spinning, and electro-spinning processes. The hagfish gel material is unique, yet its components are of general interest, since they are composed of the building blocks of many other soft biological materials. Broadening Participation of Underrepresented Groups in Engineering:The research will be integrated into the educational and outreach objective, which is to encourage diversity and broad participation of underrepresented groups in engineering. This will be achieved through the development of The Rheology Zoo, a hands-on curated library of rheologically interesting materials that will serve as a platform for outreach, engagement, and undergraduate research opportunities. Students will, for the first time, see the remarkable behavior of seemingly simple materials, see how that behavior is so important in their daily lives, and be encouraged to think creatively about new engineering opportunities for soft materials. The Zoo will be a venue for part of a six-week summer program to help incoming students transition to college, including a large number of students from underrepresented groups. Students will study interesting viscoelastic materials from The Zoo, make simple measurements, and present their work to pre-college students outside the university to further broaden exposure and recruitment to engineering. Student projects will be integrated into The Zoo, providing a self-sustaining mechanism for the collection beyond the funding life of this proposal. This research has been funded through the Broadening Participation Research Initiation Grants in Engineering solicitation, which is part of the Broadening Participation in Engineering Program of the Engineering Education and Centers Division.