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 Bombyx (B.) mori 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, B. mori 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 B. mori 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 Bacillus Subtilis 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.
","abstract_html":"<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<sup>-3</sup>, 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<sup>-3</sup>, 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>","abstract_has_math":false,"creators":["Jung, Yeojin"],"institution":null,"degree_name":"Doctor of Philosophy (Ph.D.)","degree_level":"Dissertation","degree_discipline":"Chemical Engineering","degree_department":null,"school":null,"contributors":["Xi Chen","Raymond S. Tu"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024-01-01T08:00:00Z","date_published":"2024-01-01T08:00:00Z","updated_at":"2026-07-24T01:58:07Z","subjects":["Water-responsive materials","Actuators","Actuation energy","Biomaterials","Bombyx mori silk fibroin","Chemical Engineering"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://academicworks.cuny.edu/cc_etds_theses/1153","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Xi Chen","Raymond S. 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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 Bombyx (B.) mori 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, B. mori 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 B. mori 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 Bacillus Subtilis 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.
"]},{"key":"dc:title","label":"Title","values":["Understand The Structure-Water-Responsive Relationship by Engineering Silk Materials"]}]}],"canonical_facts":{"dc:contributor":["Xi Chen","Raymond S. Tu"],"dc:creator":["Jung, Yeojin"],"dc:date.available":["2025-12-12T08:00:00Z"],"dc:description.abstract":["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 Bombyx (B.) mori 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, B. mori 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 B. mori 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 Bacillus Subtilis 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.
"],"dc:identifier":["https://academicworks.cuny.edu/cc_etds_theses/1153"],"dc:subject":["Water-responsive materials","Actuators","Actuation energy","Biomaterials","Bombyx mori silk fibroin","Chemical Engineering"],"dc:title":["Understand The Structure-Water-Responsive Relationship by Engineering Silk Materials"],"thesis:degree_discipline":["Chemical Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (Ph.D.)"]},"updated_at":"2026-07-24T01:58:07Z"}