Since their invention in the 19th century, polymers have played an essential role, yet their full potential in biomedicine remains largely untapped. Biocompatible polymers, known for their flexibility, accessibility, and modifiability, hold promise in creating complex biomimetic structures for bioscaffolds and biosensors. 3D printing, an emerging manufacturing technique, enables on-demand production of intricate structures, offering significant potential for personalized medicine and advanced biomedical engineering. This thesis focuses on designing and developing polymer-based bioscaffolds and biosensors using 3D printing. Chapter 1 provides an all-round introduction to common 3D printing techniques and polymeric biomaterials, especially biodegradable polymers. In Chapter 2, a gill-mimicking thermoelectric generator (TEG) was created to harvest body temperature and monitor bio-signals without external power. The out-of-plane geometry is obtained with fused deposition modeling (FDM), which is crucial for effective contact with various curved surfaces. Further improvements in biocompatibility enable the material to be implanted in vivo. Chapter 3 discusses UV-facilitated DIW printing for pelvic organ prolapse (POP) tissue scaffolds, featuring crosslink strategies for native tissue-like mechanical behavior. The double network comprises thiol-ene UV-initiated chemical bonds and alkaline-induced crystal regions as physical crosslink nodes. The crosslink density affects the degradation rate of the scaffold, enabling a slow degradation behavior beneficial to the recovery of the injured tissue. Chapter 4 presents a novel artificial artery design with varying moduli and natural polymers for bypass surgeries. The inner and outer layers of the conduit were stretched successively under different strains, endowing the vessel with varying moduli. Natural polymers were utilized to achieve low cytotoxicity and promote adequate cell adhesion. Additionally, the gelation behavior and the ink composition suitable for extrusion with a DIW platform were thoroughly studied. Image analysis, finite element analysis, and machine learning were employed to substantiate the findings regarding mechanical properties, extrusion quality, and printing fidelity in Chapters 3 and 4. This combination of computer-assisted analysis with experimental results enhances the robustness of the studies. Lastly, Chapter 5 provides an outlook and perspectives on the applications of biocompatible polymeric materials manufactured by 3D printing in the field of health applications.

Advancements in three-dimensional (3D) additive manufacturing techniques have opened up new possibilities for healthcare systems and the medical industry, allowing for the realization of concepts that were once confined to theoretical discussions. Among these groundbreaking research endeavors is the development of intricate magnetic structures that can be actuated through non-invasive methods, including electromagnetic and magnetic actuation. Magnetic actuation, in particular, offers the advantage of untethered operation. In this study, a photopolymerizable resin infused with Fe3O4 oxide nanoparticles is employed in the printing process using the micro-continuous liquid interface production technique. The objective is to optimize the manufacturing process to produce microstructures featuring smooth surfaces and reduced surface porosity, and enhanced flexibility and magnetic actuation. Various intricate structures are fabricated to validate the printing process's capabilities. Furthermore, the assessment of the flexibilty of these 3D-printed structures is conducted in the presence of an external magnetic field using a homemade bending test setup, allowing for a comprehensive characterization of these components. This research serves as a foundation for the future design and development of micro-robots using micro-continuous liquid interface production technique.

With increasing advance complexity in the structure to be 3D printed, the use of post processing removal of support structures has become more complicated thing due to the need of newer tool case to remove supports in such scenarios. Attempts have been made to study, research and experiment the dissolvable and recyclable photo-initiated polymeric resin that can be used to build support structure. Vat photo-polymerization method of manufacturing was selected due to wide range of materials that can be selected and researched which can have the potential to be selected further for large scale manufacturing. Deep understanding of the recyclable polymer was done by performing chemical and mechanical property test. Varying light intensities are used to study the curing properties and respective dissolving properties. In this thesis document, recyclable and dissolvable polymeric resin have been selected to print the support structures which can be later dissolved and recycled.The resin was exposed to varying light projections using grayscales of 255, 200 and 150 showing different dissolving time of each structure. Dissolving time of the printed parts were studied by varying the surface to volume ratios of the part. Higher the surface to volume ratios of the printed part resulted in lower time it takes to dissolve the part in the dissolving solution. The mechanical strengths of the recycled part were found to be pretty solid as compared to the freshly prepared resin, good sign of using it for multiple times without degrading its strength. Cactus shaped model was printed using commercial red resin and supports with the recyclable solution to deeply understand the working and dissolving properties of recyclable resin. Without any external efforts, the supports were easily dissolved in the solution, leaving the cactus intact. Further work is carried on printing Meta shaped gyroid lattice structure in effort to lower the dissolving time of the supports while maintaining enough mechanical stress. Future efforts will be made to conduct the rheology test and further lower the dissolving time as much it can to be ready for the commercial large scale applications.

Direct Ink Deposition is a type of 3D printing that utilizes a nozzle to coat thin films onto substrates. Electrospray deposition is a subcategory of Direct Ink Deposition wherein a very strong electric field is applied between the nozzle exit and the substrate, which results in the precursor polymer ink to be sprayed onto the substrate in the form of micro- or nano-droplets. As of today, its applications are limited to producing small area polymer solar cells or for biomedical applications, particularly in laboratories, but in the future, with optimization of electrospray deposition, this method can be further expanded to 3D printing components that can be used in the aerospace, automotive, and other such large-scale industries. The objective of this research is to see how application of ultrasonic vibrations during, and post deposition affects the morphology, electrical conductivity, and the respective surface properties of the thin Poly(3,4 – Ethylenedioxythipohene)-Poly(Styrenesulfonate) (PEDOT:PSS) film printed via electrospray deposition. The printing setup was previously designed and constructed, wherein the syringe was loaded with the PEDOT:PSS and Isopropyl Alcohol (IPA) solution which was then printed onto thin and small sized Indium Tin Oxide (ITO) substrates under the application of a high voltage. The distance of the nozzle from the substrate was appropriately adjusted via the vertical linear movable stage before printing, as well as the voltage supply. Deposition time was set using an Arduino code that controlled the horizontal movement of the shutter attached to the bottom of the vertical linear aluminum frame. Horizontally and vertically induced vibrations were turned on during and post deposition to analyze the effect of both on the films’ properties through an ultrasonic transducer. The electrical sheet resistance of the PEDOT:PSS films was measured using a 4-point probe device and the surface contact angle of water on the PEDOT:PSS was measured using a contact angle meter. From the results obtained, it was concluded that the application ultrasonic vibrations improved wettability compared to the films printed without any vibrations. Furthermore, the electrical sheet resistance and contact angle of pure ITO was measured as a reference.

Applications like integrated circuits, microelectromechanical devices, antennas, sensors, actuators, and metamaterials benefit from heterogeneous material systems made of metallic structures and polymer matrixes. Due to their distinctive shells made of metal and polymer, scaly-foot snails, which are found in the deep ocean, exhibit high strength and temperature resistance. Recent metal deposition fabrication techniques have been used to create a variety of multi-material structures. However, using these complex hybrid processes, it is difficult to build complex 3D structures of heterogeneous material with improved properties, high resolution, and time efficiency. The use of electrical field-assisted heterogeneous material printing (EFA-HMP) technology has shown potential in fabricating metal-composite materials with improved mechanical properties and controlled microstructures. The technology is an advanced form of 3D printing that allows for printing multiple materials with different properties in a single print. This allows for the creation of complex and functional structures that are not possible with traditional 3D printing methods. The development of a photocurable printing solution was carried out that can serve as an electrolyte for charge transfer and further research into the printing solution's curing properties was conducted. A fundamental understanding of the formation mechanism of metallic structures on the polymer matrix was investigated through physics-based multiscale modeling and simulations. The relationship between the metallic structure's morphology, the printing solution's properties, and the printing process parameters was discovered.The thesis aims to investigate the microstructures and electrical properties of metal-composite materials fabricated using EFA-HMP technology and to evaluate the correlation between them. Several samples of metal-composite materials with different microstructures will be fabricated using EFA-HMP technology to accomplish this. The results of this study will provide a better understanding of the relationship between the microstructures and properties of metal-composite materials fabricated using EFA-HMP technology and contribute to the development of new and improved materials in various fields of application. Furthermore, this research will also shed light on the advantages and limitations of EFA-HMP technology in fabricating metal-composite materials and study the correlation between the microstructures and mechanical properties.

Stereolithography (SLA) is an innovative additive manufacturing technique that has gained immense popularity in recent times due to its ability to produce complex and precise three-dimensional objects. However, the quality of the final product depends on the stability and homogeneity of the photocurable metallic ink used, which is crucial for manufacturing high-quality parts with good surface finish and higher density. To achieve homogeneity in the photocurable metallic resin, the study conducted on optimizing the printing ink for ultrafast layer less fabrication of 3D metal objects investigated the effectiveness of different dispersants such as KH 560, Triton X-100, BYK 2013, BYK 2030, and BYK 111. The use of dispersants plays a vital role in optimizing the ink and enhancing the surface finish and density of the final product. The rheology results showed that the appropriate dispersant has the potential to improve the properties of the printing ink and benefit the integrity of the printed green bodies and their surface finish. By using the optimized suspension, the study was able to fabricate parts with high metallic loading at an ultrafast speed using the Continuous Liquid Interface Production technique. FTIR analysis, sedimentation testing, and rheology study has been carried out which demonstrates the effects of the utilization of various dispersants optimally to improve the homogeneity and manufactured part’s integrity. Power law has been used to understand the viscosity behavior of dispersants in a photocurable ink with copper sulfate keeping the parameters such as shearing rate, stress, and torque intact. The microscopic images of the sintered parts showed high precision and an extremely smooth surface finish, which underscores the technique's potential to produce high-quality 3D metal objects. The solubility of dispersants significantly influenced the structural quality after washing and debinding processes. This study provides valuable information to design photocurable metallic suspensions for metal salts like copper sulfate pentahydrate.

This dissertation is focused on the rheology scaling of metal particle reinforced polymermatrix composite made of solid and nanoporous metal powders to enable their continuous 3D printing at high (>60vol%) metal content. There remained a specific knowledge gap on how to predict successful extrusion with densely packed metals by utilizing their suspension melt rheological properties. In the first project, the scaling of the dynamic viscosity of melt-extrudate filaments made of Polylactic acid (PLA) and gas-atomized solid NiCu powders was studied as a function of the metal’s volumetric packing and feedstock pre-mixing strategies and correlated to its extrudability performance, which fitted well with the Krieger-Dougherty analytical model. 63.4 vol% Filaments were produced by employing solution-mixing strategy to reduce sintered part porosity and shrinkage. After sintering, the linear shrinkage dropped by 76% compared to the physical mixing. By characterizing metal particle reinforced polymer matrix composite feedstock via flow-sweep rheology, a distinct extension of shear-thinning towards high shear rates (i.e. 100 s-1) was observed at high metal content – a result that was attributed to the improved wall adhesion. In comparison, physically mixed filament failed to sustain more than 10s-1 shear rate proving that they were prone to wall slippage at a higher shear rate, giving an insight into the onset of extrusion jamming. In the second project, nanoporous copper made out of electroless chemical dealloying was utilized as fillers, because of their unique physiochemical properties. The role of capillary imbibition of polymers into metal nanopores was investigated to understand their effect on density, zero-shear viscosity, and shear thinning. It was observed that, although the polymeric fluid’s transient concentration regulates its wettability, the polymer chain length ultimately dictates its melt rheology, which consequentially facilitates densification of pores during vacuum annealing. Finally, it was demonstrated that higher imbibition into nanopores leads to extrusion failure due to a combined effect of volumetric packing increase and nanoconfinement, providing a deterministic materials design tool to enable continuous 3D printing. The outcome of this study might be beneficial to integrate nanoporous metals into binder-based 3D printing technology to fabricate interdigitated battery electrodes and multifunctional 3D printed electronics.

Biomimetics is a field where natural and biological systems are replicated in a lab. The evolved hierarchical designs of the floating leaves of the water fern Salvinia Molesta are taken as inspiration as they reveal excellent dual scale roughness capability which also presents superhydrophobic properties in the nature. The microscale eggbeater-shaped hairs are coated with microscopic granules and nanoscopic wax crystals (dual-scale roughness) and wrinkled hydrophilic patches are coated with wax crystals which are evenly distributed on the terminal of each hair. The combination of features with diverse wettability, such as wrinkled hydrophilic patches atop superhydrophobic eggbeater hairs, makes such structures unique. The hydrophilic patches bind the air-water interface to the tips of the eggbeater hairs and inhibit air bubble formation. Salvinia effect of several Salvinia species has been extensively researched. Superhydrophobicity is attracting increasing attention for various applications. Salvinia exhibit multiscale roughness because of the unique combination of smooth hydrophilic patches on elastic eggbeater structures decorated with nanoscopic wax crystals. However, how to reproduce such hierarchical structures with controllable surface roughness is challenging for current fabrication approaches, which hinders the applications of these superhydrophobic properties as well as multi-scale roughness on surfaces in engineered products.The objective of this research is to fabricate and study the superhydrophobic structures using electrically assisted Vat Photopolymerization. In this project, an electrically assisted Vat Photopolymerization 3D printing (e-VPP-3DP) process was developed to control the surface roughness of printed eggbeater structures with distribution of multi walled carbon nanotubes (MWCNTs) for multi scale roughness. Vat Photopolymerization (VPP) is a Photopolymerization technique where a Photo Curable resin is used to rapidly produce dense photopolymer parts. A fundamental understanding of e-VPP technique to create superhydrophobic structures was studied to identify the relation between geometric morphology and mechanical enhancements of these structures. The correlation between the material properties for different weight percentage mixtures of MWCNT, printing parameters and the mechanical properties like attaching forces, surface roughness and superhydrophobic nature are also identified with this study on bioinspired hierarchical structures.

humans are currently facing issues with the high level of carbon emissions that will cause global warming and climate change, which worsens the earth’s environment. Buildings generate nearly 40% of annual global CO2 emissions, of which 28% is from building operations, and 11% from materials and construction. These emissions must be decreased to protect from further environmental harm. The good news is there is a way that carbon emissions can be decreased. The use of thermogalvanic bricks enables electricity generation by the temperature difference between the enclosure above the ceiling (i.e., the attic in a single-family home) and the living space below. A ceiling tile prototype was constructed that can make use of this temperature difference to generate electricity using an electrochemical system called a thermogalvanic cell. Furthermore, the application of triply periodic minimal surfaces (TPMS) can increase the thermal resistance of the ceiling tile, which is important for practical applications. Here, Schwarz P TPMS structures were 3D-printed from polyvinylidene fluoride (PVDF), and inserted into the electrolyte solution between the electrodes. Graphite was used as electrodes on the positive and negative sides of the tile, and Iron (II) and Iron (III) perchlorate salts were used as electrolytes. The maximum generated power was measured with different porosities of TPMS structure, and one experiment without a TPMS structure. The results indicated that as the porosity of the TPMS structure increases, the maximum power decreases. The experiment with no TPMS structure had the largest maximum power.

Ultrasound has become one of the most popular non-destructive characterization tools for soft materials. Compared to conventional ultrasound imaging, quantitative ultrasound has the potential of analyzing detailed microstructural variation through spectral analysis. Because of having a better axial and lateral resolution, and high attenuation coefficient, quantitative high-frequency ultrasound analysis (HFUA) is a very effective tool for small-scale penetration depth application. One of the QUS parameters, peak density had recently shown a promising response with the variation in the soft material microstructure. Acoustic scattering is arguably the most important factor behind different parametric responses in ultrasound spectra. Therefore, to evaluate peak density, acoustic scattering at different frequency levels was investigated. Analytical, computational, and experimental analysis was conducted to observe both single and multiple scattering in different microstructural setups. It was observed that peak density was an effective tool to express different levels of acoustic scattering that occurred through microstructural variation. The feasibility of the peak density parameter was further evaluated in ultrasound C-scan imaging. The study was also extended to detect the relative position of the imaged structure in the direction of wave propagation. For this purpose, a derivative parameter of peak density named mean peak to valley distance (MPVD) was developed to address the limitations of peak density. The study was then focused on detecting soft tissue malignancy. The histology-based computational study of HFUA was conducted to detect various breast tumor (soft tissue) grades. It was observed that both peak density and MPVD parameters could identify tumor grades at a certain level. Finally, the study was focused on evaluating the feasibility of ultrasound parameters to detect asymptotic breast carcinoma i.e., ductal carcinoma in situ (DCIS) in the surgical margin of the breast tumor. In that computational study, breast pathologies were modeled by including all the phases of DCIS. From the similar analysis mentioned above, it was understood that both peak density and MPVD parameters could detect various breast pathologies like ductal hyperplasia, DCIS, and calcification during intraoperative margin analysis. Furthermore, the spectral features of the frequency spectrums from various pathologies also provided significant information to identify them conclusively.