In the laser-induced cavitation (LIC) technique, a vapor-gas cavity is generated in water, or a soft material by focusing an intense laser pulse into the sample. The high-strain-rate mechanical properties of these samples can be investigated through a real-time size measurement of the expanding cavity bubble. Although this LIC technique has been applied to multiple research fields such as mechanical, biological and medical areas. It is possible to simplify and improve this LIC method by introducing optical-fibers. In this approach, we propose to employ an optical-fiber to deliver the intense laser pulse to an arbitrary position of an optical opaque specimen. At the same time, we also attempt to generate LIC at one end of the optical-fiber. This optical-fiber based LIC is achieved by dip-coating of the laser absorbing film on the fiber end. Thus, the film can absorb the laser pulse and generate LIC within the sample. In this study, the development of the coating material, the introduction of the optical-fiber into the existing LIC system, and the optical-fiber based LIC experiments are performed to characterize high-strain-rate mechanical properties of soft materials. We investigate the coating conditions and verify the consistency of the ablation based on the optimized coating materials. By conducting LIC experiments with gelatin samples, the feasibility of developed LIC method is investigated, LIC events are successfully formed at the fiber end which is inserted into the sample, and the rapid expanding dynamics are imaged with ultrafast stroboscopic microscopy. Using the multiple-exposure images, the expanding speeds and maximum cavity sizes are quantified to provide high-strain-rate characteristics of the soft materials. The inconsistency of the cavitation behavior resulted by the fluctuation of the coating condition and the high power intense laser conducting optical-fiber destruction can be improved by developing new coating method and new protective coating on the fiber end in the future.

<p> Block copolymers are a class of soft materials which can self-assemble into a variety of ordered structures. One method to induce new structures is the application of an external field such as an electric field. Previously, studies of the field-induced phase transitions are based on the assumption that the structural change follows certain symmetry pattern or simply using real-space numerical methods. The goal of the current project is to develop a simple analytic method to predict the structural change. Our approach is based on a linear response theory, in which the external field is taken as a perturbation and the lowest-order contribution to the solution is computed. We applied our method to the Landau-Brazovskii theory which is valid close to the order-disorder transition point of diblock copolymers. The result shows that there will be an additional term to the order parameter as a response to the external field. The structural change can be predicted by a new Fourier expansion of the order parameter. As an example, we examined the structural change of a body-centered cubic phase under an applied electric field.</p> / Thesis / Master of Science (MSc)

The research presented in this dissertation supports the overall goal of creating piezoelectric measurement technology for the analysis and characterization of soft materials that serve as feedstocks (inputs) and products (outputs) of emerging biomanufacturing processes, including cell and additive biomanufacturing processes. The first objective was to define measurement challenges associated with real-time monitoring of material compositional profiles using biosensors in practical biomanufacturing and bioprocessing formats, as insight into a material's composition (i.e., concentration of a given biologic within a material or product) provides molecular-scale insight into processes and product quality. The second objective was to design, fabricate, and characterize continuous flow cell separation technology based on 3D printed self-exciting and -sensing millimeter-scale piezoelectric transducers and microfluidic networks for separation and characterization of expanded therapeutic cells. The third objective was to establish a sensor-based characterization approach for viscoelastic properties of hydrogels and gelation processes using high-order modes of piezoelectric-excited millimeter cantilever (PEMC) sensors and understand the influence of cantilever mode number on critical sensor characteristics, including sensitivity, dynamic range, and limit of detection. The first objective was addressed through a comprehensive review of recent progress in electrochemical and hybrid biosensors, which included discussions of measurement formats, sensor performance, and measurement challenges associated with use in practical bioprocessing environments. This critical review revealed that cost, disposability, form factor, complex measurement matrices, multiplexing, and sensor regeneration/reusability are among the most pressing challenges that require solutions through advancement of sensor design and manufacturing approaches before biosensors can facilitate high-confidence long-term continuous bioprocess monitoring. The second objective was addressed by creating a microextrusion-based additive manufacturing approach for fabrication of piezoelectric-based MEMS devices that enabled integration of 3D configurations of piezoelectric transducers and microfluidic networks in a one-pot manufacturing process. The devices contained orthogonal out-of-plane piezoelectric sensors and actuators and generated tunable bulk acoustic waves (BAWs) capable of size-selective manipulation, trapping, and separation of suspended particles in droplets and microchannels. This work suggests that additive manufacturing potentially provides new opportunities for the fabrication of sensor-integrated microfluidic platforms for cell culture analysis. The third objective was addressed through resonant frequency tracking of low- and high-order modes in dynamic-mode cantilevers to enable the real-time characterization of hydrogel viscoelastic properties and continuous monitoring of sol-gel phase transitions over a wide dynamic range using practically relevant hydrogel systems used commonly in additive biomanufacturing. This work suggests that high-order modes of PEMC sensors facilitate characterization of hydrogel viscoelastic properties and gelation processes with improved dynamic range and limit of detection that can complement the performance of low-order modes. Through this research, new approaches for sensor-based characterization of soft material composition and mechanical properties using millimeter-scale piezoelectric devices are presented as solutions for current challenges in biomanufacturing and biosensing to advance capability in real-time sensing of quality attributes among biomanufactured products. / Doctor of Philosophy / The research presented in this dissertation supports the overall goal of creating sensor-based measurement technology for quality assessment of soft materials within practical online biosensing and biomanufacturing processing formats. This technology seeks to enable monitoring and control of product quality in real-time. Soft biomaterials used in these processes, including cells and hydrogels, can be characterized by quality signatures such as concentration of analytes and physical and mechanical properties. Separation and fluid handling technologies aid real-time characterization when integrated with the processing system. By improving sensor-based measurement capability of soft materials, sensing platforms can provide online quality assurance and control, thereby increasing the product quality and process efficiency – or yield– at reduced cost. The first objective was to define measurement challenges and limitations associated with detection of biologics in practical biomanufacturing and bioprocessing formats (with focus on pathogen detection, as the detection of adventitious agents and pathogens remains a critical aspect of bioprocess monitoring). This was addressed through a comprehensive review of recent progress in the field of electrochemical and hybrid biosensors. The second objective was to design and fabricate sensor-integrated microfluidic technology for cell separation applications using a combination of multi-material 3D printing and pick-and-place techniques. The third objective was to improve measurement capability of piezoelectric sensors for characterization of viscoelastic properties of hydrogel formulations commonly used in additive biomanufacturing processes and tissue engineering. Through this research, new approaches for sensor-based characterization of soft materials using millimeter-scale piezoelectric devices are presented as solutions for current challenges in biomanufacturing and biosensing platforms in order to advance quality assessment capability.

Simulations of various hydration levels of lamellar phase 23:2 Diyne PC were performed, and subsequent, serial docking simulations of a tyrosine monomer were replicated for each system in both hydrated and dehydrated states.<br>The goal was to evaluate how hydration impacts self-assembly and crystallization on the surface, and<br>whether or not these simulations, when run sequentially, could determine the answer. It was discovered that hydrated and dehydrated surfaces behave differently, and that<br>headgroup orientation plays a role in the initial docking and self-assembly process of the tyrosine monomer. It was also determined that potential energy as a sole metric<br>for determining whether or not a specific conformation of intermolecular orientation is not entirely useful, and docking scores are likely useful metrics in discriminating between conformations with identical potential energy values. <br>

The primary aim of the research in this study is to develop a robust and simple platform for the in vitro organization of cells on surfaces which facilitate rapid cell release and allows for the direct stamping of highly organized micro-tissues. Current approaches towards this goal have been very successful but are lengthy and subject cells to harsh conditions for extended periods of time raising questions regarding cell health and maintenance of physiological state. To address these concerns a platform was developed to allow for rapid cell release by utilizing a release mechanism different from previous work. Micron-scale structures comprised of the thermally responsive polymer poly(N-isopropylacrylamide) (pNIPAAm) were fabricated into various geometries to serve as a platform for cell culture. Structures were covalently confined to rigid surfaces causing non-uniform distortion of the structure's geometry upon swelling. This resulted in four primary modes of geometric distortion, or swelling-induced instability: differential lateral swelling, localized edge buckling, bulk structural buckling, and surface wrinkling. It was found that slight modifications to a linear elastic model was sufficient to predict these behaviors and provided guidance on design of the cell culture platform. Observations also suggest that a rapidly swelling structure engenders multiple forms of instability which arise as sequential and discrete steps during the swelling process. At each step the length scale of the instability increases in a step-wise fashion until the final equilibrium structure is reached. Culture of NIH 3T3 fibroblasts atop pNIPAAm structures of various geometries resulted in the growth of highly aligned micro-tissue building blocks with three distinct geometries: planar aligned micro-tissue sheets, "ribbon-like" micro-tissues, and "fiber-like" micro-tissues. Release of the micro-tissues was facilitated by the thermally-induced shape-shifting nature of micron-scale pNIPAAm structures. Release occurred rapidly (∼3 min) and required a more mild temperature shift (delta T = 9°C) than other approaches. It was found that the mechanism for cell detachment was mechanical in nature and did not require cellular activity unlike other approaches. Cell detachment was directly correlated to surface strain as a result of thermally-induced shape-shifting and has a level of dependence on cellular contractility. The platform was tested to show its capacity to directly translocate organized micro-tissues to a virgin surface. Cell transfer by direct stamping was achieved with micro-tissues retaining their shape, although stamped micro-tissues lost their organization after several hours of culture. Although the stamping process requires additional optimization, these results provide evidence that this platform has the capacity to culture and directly translocate highly organized micro-tissues. Additionally, this process provides a new, minimally invasive, approach to cell culture such that rapid construction of highly organized multi-layered tissues can be realized.

No description available.

Notre nouvelle approche expérimentale consiste à étudier la fissuration de matériaux mous, principalement des gels polymériques et colloidaux, qui ont des tailles microstructurales micrométriques. Cette augmentation de la taille microscopique va avoir pour conséquence d’augmenter la taille de la zone de process et va rendre son observation plus facile avec des moyens standard de microscopie (à transmission et confocale).Pour se faire, nous avons mis au point un nouveau dispositif expérimental pour étudier la propagation de fissures dans des matériaux mous. Cette expérience permet de faire croître une fissure de manière contrôlée dans un échantillon mou et d’inspecter la pointe de fissure à haute résolution pour des fissures se propageant entre 1 µm/s and 1cm/s. En travaillant avec des gels de polymère physiques, nous avons analyse la forme de fissure ainsi que les champs de déplacement proches pointe (en utilisant des techniques de corrélation d’image) à petites et grandes échelles et à différentes vitesses. Nous avons montré qu’il existait une séparation d’échelles spatiales entre les échelles où l’élasticité linéaire s’applique, les échelles auxquelles les non linéarités émergent et les échelles auxquelles la dissipation se produit. Cette dernière échelle n’a pas pu être investigué dans le cas de gels polymériques. De récentes expériences sur des gels colloïdaux, ayant une longueur micro-structurale plus grande que celle des gels polymers, montre que nous sommes capables de sonder en temps réel les échelles d’endommagement lors de la fissuration. / Our novel experimental approach consists in studying fracture mechanics of soft materials, mainly polymer and colloidal gels, which have microstructures with large typical length scales. This increase in the microscopic length scale will consequently increase the typical size of the process zone and make its observation easier with standard microscopy techniques (optical or confocal).To do so, we designed a novel experimental device to study crack propagation in such soft materials. This experiment enables us to grow a unique crack in a controlled way in a soft specimen and to look at the crack tip at high magnification for crack velocities between 1 µm/s and 1cm/s. Working on physical polymer gels, we analysed the crack shape and crack displacement fields (using Digital Image Correlation) at large and intermediate scales for various velocities. We realized there was a separation of scales between the scale at which LEFM applies, the scale at which elastic nonlinearities emerge and the scale at which dissipation occurs. This last scale could not be investigated with the polymer gel. Recent experiments on colloidal gels, which have a microscopic length scale bigger than the one of polymer gels, show that we are able to probe damage at the microstructural scale.

As an intrinsic requirement for digital image correlation (DIC)to be applicable, the images must exhibit a speckle pattern of sufficient unique features. Researchers have incorporated X-ray phase contrast imaging (PCI) and DIC (XDIC) and conducted studies on materials with natural internal features as speckles. This study is the first attempt to explore the applicability and standards of XDIC to be applied on materials that are transparent under X-ray PCI, mainly polymers, by deliberately embedding particles into the sample. The goal is to generate a high-quality speckle while maintaining the least influence on the material’s properties. Iron oxide (FeO), tungsten carbide (WC), and platinum (Pt) are embedded into Sylgard® epoxy at various weight ratios, and the Sylgard® samples are loaded with a Kolsky compression bar paired with high-speed X-ray PCI. The speckle quality of the PCI images is assessed using a mean intensity gradient based approach, as well as intensity distribution analysis. DIC is applied to the images to measure the displacement field in the loading direction, and the results are analyzed. The engineering stress-strain relationship is generated from the Kolsky bar apparatus, and the results are compared to find the influence of the added particles.<div><br></div><div>The results indicate thatthe addition of particles does not significantly alter the base polymer’s properties, and the theoretical deviation error can be as low as less than 0.01 pixels. Disregarding the limited applicability to embed into polymer samples, platinum produces the best speckle. WC particle is the superior choice of material to embed for its good speckle quality, ease of embedding, and good availability. Lower weight ratios are shown to be preferential. This study also emphasizes the importance of sample design when applying XDIC to materials with embedded particles. It is preferential for best accuracy to design the region of interest to be away from the surfaces of the samples and be located near the back of the sample with respect to the impact surface.<br></div>

<p dir="ltr">The recent COVID-19 pandemic has emphasized the risk of respiratory infections leading to acute respiratory distress syndrome (ARDS). A significant factor contributing to poor ARDS outcomes is the impairment of lung surfactant due to infiltrating surface-active proteins and phospholipases during lung inflammation. Lung surfactant's vital role in stabilizing alveoli by reducing air-water interfacial tension becomes evident as its dysfunction severely compromises respiratory function. Although lung surfactant (LS) replacement therapy effectively addresses neonatal LS deficiencies, its efficacy in ARDS treatment for adults remains limited. The challenge lies in the chemical similarity between current animal-extracted surfactants and human lung surfactant which are both phospholipid-based. To address this issue, this dissertation outlines a transformative "polymer lung surfactant (PLS)" designed to overcome the limitations of conventional exogenous surfactants in treating ARDS.</p><p dir="ltr">Firstly, a formulation method, referred to as equilibration-nanoprecipitation (ENP), is established which achieves reproducibility, controls sizing, and limits dispersity of the PLS formulation consisting of block copolymer (BCP) kinetically "frozen" micelles/nanoparticles suspended in water. The method uses a two-step approach of 1) equilibrating the BCP nanoparticles in a water/co-solvent mixture and 2) removing co-solvent using dialysis against a large water reservoir. Comparison of ENP with a conventional solvent-exchange technique through experimental and computational analysis yields further insights into ENP's advantages.</p><p dir="ltr">Next, various studies are highlighted which provide fundamental characterizations of the air-water surface behavior and physical properties of BCP nanoparticles in water. The air-water surface properties of block copolymers have been studied extensively when spread as free chains in organic solvent; however, little was previously known about air-water interfacial behavior of water-spread polymer nanoparticles. The studies address such topics as the effect of nanoparticle size, effect of nanoparticle core chemistry, and the effect of temperature on surface-mechanical behavior. Insights into nanoparticle molecular structure at the interface are provided through X-ray reflectivity and grazing incidence X-ray diffraction. The effect of temperature is further characterized by developing novel NMR and Langmuir trough methods to determine the physical state (glassy vs rubbery) of the core domain in the nanoconfined state at temperatures above and below physiologic temperature.</p><p dir="ltr">Lastly, <i>in vivo </i>studies are presented which demonstrate the detailed and promising proof-of-concept results on the efficacy of the PLS technology in mouse models of lung injury. The PLS therapy not only improves biomechanical function of the lung, but it also significantly lowers the extent of lung injury as shown by histological analysis and inflammatory marker measurements. An additional <i>in vivo </i>study is presented which highlights challenges in the delivery of the liquid PLS suspension to the lungs. The <i>in vivo </i>studies ultimately provide solid motivation for continued research into the development of the PLS therapy.</p><p dir="ltr">Given the promising potential of the PLS technology shown in the <i>in vivo</i> studies, the materials characterizations shared in this presentation offer valuable insights into the design of a novel PLS therapy. From these insights, key design parameters such as nanoparticle size characteristics, core chemistry, and core molecular weight can be chosen to produce the most desirable material properties. Overall, this dissertation furthers the progress of PLS therapeutic development and will hopefully ultimately contribute to improved health outcomes in patients suffering from ARDS.</p>

Chapter 1. Introduction This chapter is an overview on the literature of self-association of small organic molecules. The chapter is presented in four parts. First, an introduction to aggregation of small molecules is given with the emphasis on micelles and gels(Parts 1 and 2) In part 3, a short overview is given on bile acid based aggregates and their applications. Lastly, the content of the thesis is outlined. Chapter 2. Solution properties of novel cationic bil salts: A structure-aggregation property study Scheme 1: Structures of Cationic bile salts(Refer PDF File) Bile Salts are biosurfactants and they are known to form micelles in aqueous medium. We studied the micellar properties of cationic bile salts(Scheme 1) and compared with their natural (anionic) counterparts. A serendipitous discovery of the gelation of a cationic bile salt(4) led us to investigate the aggregation properties of this new class of cationic hydrogelators. This chapter highlights the recent efforts on the study of side chain structure-aggregation property relationship of cationic bile salts. Bile acid analogues with a quaternary ammonium group(Scheme 1, compounds 2, 3, 4, 6, 8 and 12) on the side chain were found to efficiently gel aqueous salt solutions. Some of the cationic bile salts gelled water alone and many of them gelled aqueous salt solutions even in the presence of organic co-solvents(≤ 20%) such as ethanol, methanol, DMSO and DMF. A strong counter ion dependent gelation was observed. These gels showed interconnected fibrous networks. Unlike natural anionic bile salt gels(reported for NaDC, NaLC), the cationicgels reported here are pH independent. Cationic gels derived from DCA showed more solid-like rheological response compared to natural NaDC gels studied earlier by Tato et al. A strong structure(side-chain) andcounter-ion dependent flow of the cationic bile salt gels was seen. Chapter 3. Applications of cationic bile salts and their aggregates Cationic bile salts are useful in many ways. We have studied some of the applications of cationic bile salts(discussed in chapter 2) and their aggregates in this chapter. The chapter is presented in three parts. Part 1. Interaction of Cationic bile salts and DNA The bile acid amphiphilicity is believed to help the DNA binding process of polyamines. This has prompted us to study the DNA-bile salt binding interaction of bile salts. The binding of cationic bile salts has been expressed in terms of C50 values, which were determined from the plot of fluorescence of ethidium bromide bound DNA vs. bile salt concentration(Fig 1) The C50 values for cationic bile salts were estimated to be about 1.2 mM. Fig1: A plot of fluorescene of ethidium bromide bound DNA against bile salt concentration (Refer PDF File) Part 2. Cholesterol solubilization and crystallization studies in aqueous bile salt solutions. Dihydroxy bile salt micelles are well known for cholesterol dissolution(e.g. UDCA and CDCA). We studied the dissolution of cholesterol in the cationic bile salt micelles(of 21-25) and the results are discussed in this part. Scheme 2: Cationic bile salt chlorides studied for cholesterol dissolution (Refer PDF File) A powder dissolution method was used to study the solubility of anhydrous cholesterol in cationic bile salt solution. These cationic bile salt micelles can dissolve cholesterol to the same extent as the taurine conjugates of bile acids, but lesser than the natural anionic bile salts(Fig.2) Addition of PC(Phosphatidylcholine) to cationic bile salt micelles enhanced the micellar cholesterol solubilization. Fig 2:Cholesterol dissolution in cationic bile salt solutions(Refer PDF File) The crystal nucleation time of cholesterol did not change significantly by adding 5-30 mM of the cationic bile salts. The bile salt analogues did, however, attenuate cholesterol crystallization to a similar extent at all concentrations studied. All these effects wer comparable to those fo cholic acid. Part 3. Hydrogels as a reaction vessel for photodimerization Bile salt micelles have been shown to control the product selectivity in photochemical reactions. The dynamic nature of the bile salt micelles results in differential effects on reaction selectivity. The photodimerization of acenaphthylene(sheme 3) was studied in micellar and hydrogel medium(e.g. NaDC, 22, 28, etc.) The ratio of anti- to synphotodimer was found to be greater in gel bound state than in solution. Substitution on the CAN ring did not show larger variation on the product distribution from solution gel. Scheme 3: Photodimerization of acenaphthylene(Refer PDF File) Chapter 4. Bile acid derived sulfur analogues in designing novel materials. Part 1. A simple approach towards nanoparticle-gel hybrid material. Scheme 4: Scheme for the synthesis of thiols derived from bile acids (Refer PDF File) Our interest in bile acid based gelator molecules led us to explore the synthesis and properties of bile analogues with the side chain carboxylic acid replaced by a thiol(Scheme 4) to stabilize metal NPs. We reasoned that the specific self-aggregation modes of facially amphiphilic bile units would enable a metal NP capped by such a thiol to “lock” onto a gel fiber derived from a structurally related gelator molecule. AuNPs stabilized by 38-40 were obtained by the NaBH4 reduction of homogeneous methanolic solutions of the thiol and gold salt. These steroid capped nanoparticles were found to stay dispersed in a gel of 28, thus providing a simple approach to obtain gel-nanoparticle hybrid. A photograph of the hybrid material and their morphology are shown in Fig 3.(Refer PDF File) Chart 1: Structure of the gelator used for designing a hybrid material(Refer PDF File) Part 2. Gelation of aromatic solvents using sulfur analogues of bile acid A few of the sulfur derivatives were serendipitously fouond to gel organic solvents (Fig 4). Thiol 38 formed stable gels at room temperatures while the disulphide 36 formed stable gels below 5º C. The aggregation properties, morphology, and the melting profiles of gels of disulfides and thiols derived from bile acids have been highlighted in this part. Fig 4: A photograph of the gels derived from 38(Refer PDF File) (For Figures and Molecular Formula Pl refer the Original Thesis)