Collaborative Research: Exploring the Role of Ultra-Soft Inclusions in the Mechanics of Fibrous Materials

North Carolina State University, Raleigh NC

Investigators

Abstract

In nature, fibrous materials such as biological tissues can display adaptive behaviors. These include tunable density, stiffness, and permeability, which allow them to carry mechanical loads, respond to environmental stimuli, and heal wounds. These behaviors are achieved through ultra-soft inclusions like cells and platelets, and their interactions with the surrounding fibrous network, collectively lending their host materials specialized functions. Mimicking such functions in engineered materials requires a deep understanding of the mechanical role of ultra-soft inclusions in fiber networks at large deformations. This award supports fundamental research on how ultra-soft inclusions interact with a network of fibers and how these small-scale interactions affect the overall deformation behavior of the host material. The findings from this investigation will not only provide new insights into the design and fabrication of bio-inspired, adaptive materials for diverse applications in smart textiles and wearable technology, wound healing, filtration membranes, and soft robotics, but it will also lead to a better understanding of physiological and pathological processes in biological tissues that are driven by ultra-soft inclusions in the form of cells and cell-like particles, consequently advancing the national health, prosperity, and welfare. In addition to benefitting the broader scientific community, this work will also support undergraduate and graduate education through new, interdisciplinary class modules, research opportunities, and a trans-institutional visitation program. An additional broader impact will be through an education outreach program aimed at middle school students in collaboration with a Department of Defense-affiliated STEM youth program in Austin, TX, inspiring the students to recognize the universality of many engineering principles spanning from biomedical engineering to civil and mechanical engineering. Micron-sized, ultra-soft inclusions in fiber networks are ubiquitous in natural materials and play a critical role in the overall mechanical properties despite their small size. This award aims to understand how controlled microscale, local and non-local interactions of highly deformable inclusions with semi-flexible fiber networks lead to emergent behaviors at macroscales in engineered materials. The focus is on polymeric (fibrous) host materials for their importance in both engineering applications and nature. Computational approaches combine surface-enriched numerical tools accounting for bulk and surface adhesion, elastocapillary effects, soft solid-beam contact phenomena, and data-driven homogenization to predict the mechanics of polymer-particle composites. Critically, this project develops a controllable, experimental microgel platform to make and study ultra-soft inclusions with highly tunable mechanical properties. An iterative feedback loop between theory, computations, and micro- and macroscale experiments using the microgel material platform is central to the project for validating predictions and informing the model development. Ultimately, this project will provide a quantitative knowledge base and a microgel synthesis platform to demonstrate that the material design space of composites with ultra-soft inclusions can be precisely tuned through control of the nonlinear local/nonlocal interactions between ultra-soft inclusions and fibrous networks. 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.