Understand The Structure-Water-Responsive Relationship by Engineering Silk Materials

<p>Water-responsive (WR) materials mechanically swell and shrink in response to changes in relative humidity, and they have demonstrated the capability to exert higher actuation energy than conventional actuators and artificial muscles. As a result, WR materials have recently gained attention as potential high-energy actuating components for engineering applications. Despite the growing interest in this emerging category of WR materials, the fundamental WR mechanism of their significant performance is still not fully understood, limiting the ability to rationally design engineered systems. This dissertation presents three approaches for understanding the water-responsiveness of materials by engineering <em>Bombyx (B.) mori</em> silkworm silk protein. First, by increasing the silk’s mechanical stiffness as a result of increased silk II structures (β-sheet rich domains) or adding stiff silica nanoparticles, <em>B. mori</em> silk’s WR actuation energy density was dramatically increased from 0.2 to 1.6 MJ m^-3, surpassing the energy densities of all known natural muscles. Second, we achieved a remarkable enhancement in the WR energy density of <em>B. mori</em> silk, reaching 3.1 MJ m^-3, by adjusting silk’s nano-porosity. Throughout these studies, silk’s programmable secondary structures, mechanical properties, as well as pore structure-dependent water properties were found to play a crucial role in silk's WR behaviors. Third, to further explore the potential for scaling up silk-based WR materials, WR silk composite fibers were developed by coupling nanoscale <em>Bacillus Subtilis</em> peptidoglycan (PG) with silk using a wet-spinning technique. This work provides proof-of-concept demonstrations that use high-energy, muscle-like WR actuators for real-world applications.</p>

Name thesis:degree_name

Doctor of Philosophy (Ph.D.)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemical Engineering

Year dc:date.available

2024

Author dc:creator

• Jung, Yeojin

Contributors dc:contributor

• Xi Chen
• Raymond S. Tu

• Water-responsive materials
• Actuators
• Actuation energy
• Biomaterials
• Bombyx mori silk fibroin
• Chemical Engineering

Repository record dc:identifier

https://academicworks.cuny.edu/cc_etds_theses/1153

OAI identifier oai:identifier

oai:academicworks.cuny.edu:cc_etds_theses-2201