Multi-frame Interferometric Imaging with a Femtosecond Stroboscopic Pulse Train for Observing Irreversible Phenomena

We describe a high-speed single-shot multi-frame interferometric imaging technique enabling multiple interferometric images with femtosecond exposure time over a 50 ns event window to be recorded following a single laser-induced excitation event. The stroboscopic illumination of a framing camera is made possible through the use of a doubling cavity which produces a femtosecond pulse train that is synchronized to the gated exposure windows of the individual frames of the camera. The imaging system utilizes a Michelson interferometer to extract phase and ultimately displacement information. We demonstrate the method by monitoring laser-induced deformation and the propagation of high-amplitude acoustic waves in a silicon nitride membrane. The method is applicable to a wide range of fast irreversible phenomena such as crack branching, shock-induced material damage, cavitation and dielectric breakdown

Experimental developments and studies of systems far from equilibrium

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, February, 2021Cataloged from the official PDF of thesis.Includes bibliographical references.Advances to shock wave generation and characterizations techniques are presented. Building upon previous work employing a novel quasi-2D focusing geometry, pressures of at least 100 GPa are achieved on the benchtop at the micron scale. Diagnostics for optical visualization of these generated waves were also refined; an existing single-shot multiframe imaging technique was extended into phase sensitive imaging. These techniques are applied to a range of material systems (energetic materials, brittle solids and biological membranes), pushing them far from equilibrium, and studying their response. While the explosive 1,3,5-triaza-1,3,5-trinitrocyclohexane (RDX), has been used for almost a century, questions remain about its initiation, reactivity, and interaction with shock waves. Very little work has directly addressed the coupling between mechanical deformation and chemistry in this system. Further, the literature to date mostly comprises studies with idealized 1-dimensional waves.Herein, the reactivity of single crystals of RDX responding to multiple shockwaves is considered. A surprising transient sensitivity to low pressure reflected shockwaves following a high-pressure initial excitation is discovered. This effect confirms the link between morphological change, and sensitivity previously reported. Silica glass is a widely studied system under shock compression and high pressure. A relatively low pressure phase transition is known and several distinct amorphous states exist prior to the transition. Several studies have also reported a lagging wave following dynamic compression in glasses. This "failure wave" is thought to precede fracture and brittle failure. We demonstrate a method of generating shock waves in glass and show the ability to image the dynamics in real-time. Additionally, we directly image fracture following shock compression and an associated failure wave. Finally, we address the interaction of shock and acoustic waves with cell membranes.This interaction is of great interest in biomedical technology for targeted cell lysing, as well as drug and vaccine delivery. Basic science questions also exist regarding the interactions between these waves and biological cells and membranes. Here we employ simultaneous interferometric and fluorescence imaging to elucidate the mechanism of transmembrane transport in cells and cell models. We show that under single cycle shock conditions the spatial structure of the wave is key to transfection; the wave must be spatially narrower than the cell itself. However, in a multicycle acoustic case spatially wider waves can still affect transfection suggesting that we have moved from a mechanism relying on a pressure gradient across the cell (in the shock case) to a pore formation mechanism.by Dmitro Jaroslau Martynowych.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Chemistr

Synthesis of Indole Scaffolds, From Simple Precursors, Through a Mild Global Reductive Methodology

Complex indole structures have wide application in pharmaceuticals, and materials science. Many synthetic routes to these types of structures suffer from excessive cost, harsh conditions, or lack of substitution. This thesis focuses on the development of a mild, practical, and versatile synthesis of these complex structures. A highly regioselective [3+2] dipolar cycloaddition yielding nitro-substituted isoxazolines was optimized. Conditions were then developed and optimized, utilizing Feº and NH4Cl for the facile reduction of these nitro-isoxazoline systems into indoles

Interferometric and fluorescence analysis of shock wave effects on cell membrane

Shock waves generated by laser pulses have been gaining attention for biological and medical applications in which shock-induced cell membrane deformation influences cell permeation. However, the mechanisms through which the deformation of cell membranes affects permeability remain mostly unknown because of the difficulty of observing in real time the transient and dynamic behaviors of the shock waves and the cells. Here we present an all-optical measurement method that can quantitatively capture the pressure distribution of the propagating shock wave and simultaneously monitor the dynamic behavior of cell membranes. Using this method, we find that the profile of the shock wave dictates the cell membrane permeation. The results suggest a possible mechanism of membrane permeation where sharp pressure gradients create pores on the membrane. Our measurement will foster further understanding of the interaction of shock waves with cells, while the proposed mechanism advances biological and medical applications of shock waves.U.S. Army Research Office (Contract W911NF-18-2-0048

Converging-diverging shock-driven instabilities along soft hydrogel surfaces

Intense surface eruptions are observed along the curved surface of a confined cylindrical film of hydrogel subject to laser-induced converging-diverging shock loading. Detailed numerical simulations are used to identify the dominant mechanisms causing mechanical instability. The mechanisms that produce surface instability are found to be fundamentally different from both acoustic parametric instability and shock-driven Richtmyer-Meshkov instability. The time scale of observed and simulated eruption formation is much larger than that of a single shock reflection, in stark contrast to previously studied shock-driven instabilities. Moreover, surface undulations are only found along external, as opposed to internal, soft solid boundaries. Specifically, classic bubble surface instability mechanisms do not occur in our experiments and here we comment only on the new surface undulations found along the outer boundary of solid hydrogel cylinders. Our findings indicate a new class of impulsively excited surface instability that is driven by cycles of internal shock reflections. </p

Single-Shot Multi-Frame Imaging of Cylindrical Shock Waves in a Multi-Layered Assembly

Abstract We demonstrate single-shot multi-frame imaging of quasi-2D cylindrically converging shock waves as they propagate through a multi-layer target sample assembly. We visualize the shock with sequences of up to 16 images, using a Fabry-Perot cavity to generate a pulse train that can be used in various imaging configurations. We employ multi-frame shadowgraph and dark-field imaging to measure the amplitude and phase of the light transmitted through the shocked target. Single-shot multi-frame imaging tracks geometric distortion and additional features in our images that were not previously resolvable in this experimental geometry. Analysis of our images, in combination with simulations, shows that the additional image features are formed by a coupled wave structure resulting from interface effects in our targets. This technique presents a new capability for tabletop imaging of shock waves that can be extended to experiments at large-scale facilities

Imaging of photoacoustic-mediated permeabilization of giant unilamellar vesicles (GUVs)

© 2021, The Author(s). Target delivery of large foreign materials to cells requires transient permeabilization of the cell membrane without toxicity. Giant unilamellar vesicles (GUVs) mimic the phospholipid bilayer of the cell membrane and are also useful drug delivery vehicles. Controlled increase of the permeability of GUVs is a delicate balance between sufficient perturbation for the delivery of the GUV contents and damage to the vesicles. Here we show that photoacoustic waves can promote the release of FITC-dextran or GFP from GUVs without damage. Real-time interferometric imaging offers the first movies of photoacoustic wave propagation and interaction with GUVs. The photoacoustic waves are seen as mostly compressive half-cycle pulses with peak pressures of ~ 1 MPa and spatial extent FWHM ~ 36 µm. At a repetition rate of 10 Hz, they enable the release of 25% of the FITC-dextran content of GUVs in 15 min. Such photoacoustic waves may enable non-invasive targeted release of GUVs and cell transfection over large volumes of tissues in just a few minutes

Imaging of photoacoustic-mediated permeabilization of giant unilamellar vesicles (GUVs)

Target delivery of large foreign materials to cells requires transient permeabilization of the cell membrane without toxicity. Giant unilamellar vesicles (GUVs) mimic the phospholipid bilayer of the cell membrane and are also useful drug delivery vehicles. Controlled increase of the permeability of GUVs is a delicate balance between sufficient perturbation for the delivery of the GUV contents and damage to the vesicles. Here we show that photoacoustic waves can promote the release of FITC-dextran or GFP from GUVs without damage. Real-time interferometric imaging offers the first movies of photoacoustic wave propagation and interaction with GUVs. The photoacoustic waves are seen as mostly compressive half-cycle pulses with peak pressures of ~ 1 MPa and spatial extent FWHM ~ 36 µm. At a repetition rate of 10 Hz, they enable the release of 25% of the FITC-dextran content of GUVs in 15 min. Such photoacoustic waves may enable non-invasive targeted release of GUVs and cell transfection over large volumes of tissues in just a few minutes