Date of Defense
16-4-2026 11:00 AM
Location
F1-1043
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Mechanical Engineering
College
COE
Department
Mechanical and Aerospace Engineering
First Advisor
Prof. Abdel-Hamid. I. Mourad
Keywords
Energy absorption, impact resistance, metamaterials, bio-inspiration, biomimicry, hydrogels, bioprinting.
Abstract
Nature has always played the role of a design cue for several targeted engineering applications, with designers attempting to mimic the characteristics of natural organisms to have significant advantages in the engineering performance cycle. This dissertation explores the relationship between bioinspired design parameters and material compositions in diverse engineering applications, ranging from mechanical energy absorption to tissue engineering applications. A two-fold objective was followed in the study, where the initial focus was based on the structural design of metamaterial lattices based on geometrical cues observed in the horn structure of bighorn sheep and cuttlebone microstructure of cuttlefish. The advances made in additive manufacturing, such as Multi-Jet Fusion (MJF) and 3D extrusion-based bioprinting techniques, were employed as a tool to realize the concepts into parts, for experimental characterization studies in mechanical and biomedical studies, respectively.
The first part of the dissertation was based on introducing novel designs, developing architected metamaterial unit cells, drawing inspiration from the structural attributes of bighorn sheep horns and cuttlebone microstructure. The performance of both the developed lattices was assessed in quasi-static compression tests, whereas low-velocity impact studies were also carried out for the horn-inspired lattices. For the quasi-static compression behaviour of the horn-inspired lattices, the impact of two key geometrical features of the sheep horn, curvature and tapering, on mechanical performance was explored through experimental tests and finite element analysis. The findings revealed that horn-inspired lattice structures improve specific energy absorption by 25.4% compared to similar structures without tapering and curvature, and a 52.8% enhancement in specific energy absorption compared to conventional designs, such as Kelvin foam. It was observed that, unlike the quasi-static results, only the bending curvature, without any effect of tapering, contributed to improvement in specific energy absorption for the low-velocity impact studies. This was attributed to a high-speed deformation pattern and structural separation observed in tapered sections during impact tests. The novel cuttlebone-inspired structures were developed, considering the wall waviness found in asymmetric walls of the cuttlebone microstructure as a geometrical design parameter. The results indicated significant improvement in specific energy absorption upto 6.4 times for the Design I case, with only in-plane waviness in the structure and 4.6 times for the Design II case, with the sinusoidal walls undergo a 180° phase shift through the thickness along with the in-plane waviness, respectively, compared to the control case with zero wall waviness. It was shown that the unique structural characteristics of bighorn sheep horns and cuttlebone microstructure provide valuable insights for developing energy-absorbing structures, highlighting their potential for applications that demand efficient energy management in lightweight designs.
The second half of the dissertation is based on developing novel bioinspired hydrogel compositions for 3D bioprinting-based osteochondral tissue engineering studies. Novel material combinations of plant and animal-derived constituents were subjected to various characterization studies for printability, material and biological tests to validate the applicability of the developed hydrogels. In the first case, a composite hydrogel based on gelatin methacryloyl (GelMA) and oxidized inulin was successfully crosslinked and subjected to primary characterization, including cytotoxicity as well as mechanical characterization, to validate stiffness-induced chondrogenic differentiation of adipose-derived mesenchymal stem cells (AD-MSCs). For the second hydrogel composition based on sodium alginate, xanthan gum and porcine-derived collagen, the aim was to comparatively evaluate the chondrogenic and osteogenic differentiation potential of AD-MSCs encapsulated within biomaterial-based hydrogel constructs fabricated using 3D bioprinting technology. Post-printing cell viability and morphology were assessed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and DAPI (4',6-diamidino-2-phenylindole) staining to ensure cytocompatibility of the bio-inks and printing process. Following initial validation, the bioprinted constructs were subjected to lineage-specific induction using chondrogenic and osteogenic differentiation media. The extent of differentiation was evaluated through established histochemical staining techniques, including Alcian Blue for cartilage-specific matrix deposition, and Alizarin Red S and ALP for mineralized bone matrix formation. The comparative investigation provides valuable insights into the performance of bioprinted hydrogel-based constructs for cartilage and bone tissue engineering, supporting their potential application in regenerative and reconstructive therapies.
Included in
BIO-INSPIRED MATERIALS AND METAMATERIALS FOR TUNABLE BIOMIMETIC PROPERTIES IN DIVERSE ENGINEERING APPLICATIONS
F1-1043
Nature has always played the role of a design cue for several targeted engineering applications, with designers attempting to mimic the characteristics of natural organisms to have significant advantages in the engineering performance cycle. This dissertation explores the relationship between bioinspired design parameters and material compositions in diverse engineering applications, ranging from mechanical energy absorption to tissue engineering applications. A two-fold objective was followed in the study, where the initial focus was based on the structural design of metamaterial lattices based on geometrical cues observed in the horn structure of bighorn sheep and cuttlebone microstructure of cuttlefish. The advances made in additive manufacturing, such as Multi-Jet Fusion (MJF) and 3D extrusion-based bioprinting techniques, were employed as a tool to realize the concepts into parts, for experimental characterization studies in mechanical and biomedical studies, respectively.
The first part of the dissertation was based on introducing novel designs, developing architected metamaterial unit cells, drawing inspiration from the structural attributes of bighorn sheep horns and cuttlebone microstructure. The performance of both the developed lattices was assessed in quasi-static compression tests, whereas low-velocity impact studies were also carried out for the horn-inspired lattices. For the quasi-static compression behaviour of the horn-inspired lattices, the impact of two key geometrical features of the sheep horn, curvature and tapering, on mechanical performance was explored through experimental tests and finite element analysis. The findings revealed that horn-inspired lattice structures improve specific energy absorption by 25.4% compared to similar structures without tapering and curvature, and a 52.8% enhancement in specific energy absorption compared to conventional designs, such as Kelvin foam. It was observed that, unlike the quasi-static results, only the bending curvature, without any effect of tapering, contributed to improvement in specific energy absorption for the low-velocity impact studies. This was attributed to a high-speed deformation pattern and structural separation observed in tapered sections during impact tests. The novel cuttlebone-inspired structures were developed, considering the wall waviness found in asymmetric walls of the cuttlebone microstructure as a geometrical design parameter. The results indicated significant improvement in specific energy absorption upto 6.4 times for the Design I case, with only in-plane waviness in the structure and 4.6 times for the Design II case, with the sinusoidal walls undergo a 180° phase shift through the thickness along with the in-plane waviness, respectively, compared to the control case with zero wall waviness. It was shown that the unique structural characteristics of bighorn sheep horns and cuttlebone microstructure provide valuable insights for developing energy-absorbing structures, highlighting their potential for applications that demand efficient energy management in lightweight designs.
The second half of the dissertation is based on developing novel bioinspired hydrogel compositions for 3D bioprinting-based osteochondral tissue engineering studies. Novel material combinations of plant and animal-derived constituents were subjected to various characterization studies for printability, material and biological tests to validate the applicability of the developed hydrogels. In the first case, a composite hydrogel based on gelatin methacryloyl (GelMA) and oxidized inulin was successfully crosslinked and subjected to primary characterization, including cytotoxicity as well as mechanical characterization, to validate stiffness-induced chondrogenic differentiation of adipose-derived mesenchymal stem cells (AD-MSCs). For the second hydrogel composition based on sodium alginate, xanthan gum and porcine-derived collagen, the aim was to comparatively evaluate the chondrogenic and osteogenic differentiation potential of AD-MSCs encapsulated within biomaterial-based hydrogel constructs fabricated using 3D bioprinting technology. Post-printing cell viability and morphology were assessed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and DAPI (4',6-diamidino-2-phenylindole) staining to ensure cytocompatibility of the bio-inks and printing process. Following initial validation, the bioprinted constructs were subjected to lineage-specific induction using chondrogenic and osteogenic differentiation media. The extent of differentiation was evaluated through established histochemical staining techniques, including Alcian Blue for cartilage-specific matrix deposition, and Alizarin Red S and ALP for mineralized bone matrix formation. The comparative investigation provides valuable insights into the performance of bioprinted hydrogel-based constructs for cartilage and bone tissue engineering, supporting their potential application in regenerative and reconstructive therapies.