Μm Resolution Research Articles

Direct observation on supersonic microprojectile penetration of carbon fiber composites with ultrafast synchrotron X-ray phase contrast imaging

High-speed penetration into carbon fiber composites is of fundamental importance to materials science and impact engineering, but research along this line suffers considerably from the lack of direct experimental observations. Here we investigate such penetration dynamics of a unidirectional carbon fiber reinforced epoxy (UCFRE) composite, with a combination of in situ, ultrafast, synchrotron phase contrast imaging and finite element (FE) analysis. The experiments yield the first direct observation on projectile trajectories and fiber-scale deformation and damage in the UCFRE composites during supersonic microprojectile penetration, for different fiber orientations (0∘−90∘ from the impact direction) and projectile velocities 600−850m.s-1, at unprecedented temporal (∼100 ps) and spatial (5 μm) resolutions. The maximum penetration depth decreases with increasing fiber orientation angles, as a result of anisotropic damage evolution in the composite sample. Strain localizations are prone to develop along a direction perpendicular to the fiber orientation, while the damage or cavity region, along the fiber direction. FE modeling with a three-dimensional Hashin criterion yields consistent projectile trajectory and cavity morphology with the experimental results. With increasing fiber orientation angles, damage analyses show a transition in the damage mode from fiber compression to matrix compression damage, in line with the increasing maximum penetration depth.

Fabrication of Tapered 3D Microstructure Arrays Using Dual-Exposure Lithography (DEL).

Three-dimensional (3D) microstructure arrays (MSAs) have been widely used in material science and biomedical applications by providing superhydrophobic surfaces, cell-interactive topography, and optical diffraction. These properties are tunable through the engineering of microstructure shapes, dimensions, tapering, and aspect ratios. However, the current fabrication methods are often too complex, expensive, or low-throughput. Here, we present a cost-effective approach to fabricating tapered 3D MSAs using dual-exposure lithography (DEL) and soft lithography. DEL used a strip-patterned film mask to expose the SU-8 photoresist twice. The mask was re-oriented between exposures (90° or 45°), forming an array of dual-exposed areas. The intensity distribution from both exposures overlapped and created an array of 3D overcut micro-pockets in the unexposed regions. These micro-pockets were replicated to DEL-MSAs in polydimethylsiloxane (PDMS). The shape and dimension of DEL-MSAs were tuned by varying the DEL parameters (e.g., exposure energy, inter-exposure wait time, and the photomask re-orientation angle). Further, we characterized various properties of our DEL-MSAs and studied the impact of their shape and dimension. All DEL-MSAs showed optical diffraction capability and increased hydrophobicity compared to plain PDMS surface. The hydrophobicity and diffraction angles were tunable based on the MSA shape and aspect ratio. Among the five MSAs fabricated, the two tallest DEL-MSAs demonstrated superhydrophobicity (contact angles >150°). Further, these tallest structures also demonstrated patterning proteins (with ~6–7 μm resolution), and mammalian cells, through microcontact printing and direct culturing, respectively. Our DEL method is simple, scalable, and cost-effective to fabricate structure-tunable microstructures for anti-wetting, optical-, and bio-applications.

A study of antioxidant and antibacterial activity using honey mediated Chromium oxide nanoparticles and its characterization

Honey is authenticated as the world’s prehistoric food source with incomparable therapeutic, biochemical, physical, and curative values. Chromium oxide nanoparticles were precipitously generated by reduction of potassium dichromate solution in collaboration with natural honey holding carbohydrates as a chief component which perform as reducing agent. The outcome suggests that water soluble carbohydrates have aldehyde group cause the formation of Cr2O3 nanoparticles. The properties of the prepared Cr2O3 nanoparticles were characterized using several techniques such as UV–Visible, FT-IR, SEM, EDAX, XRD and AFM. The FT-IR studies reveals that the broad band of low intensity at 1165.00 cm−1 can be found to be the surface Cr-O stretching vibrations. The SEM image illustrates the rocky structure of the prepared nanoparticle. The AFM image exhibits the topography of Cr2O3nanoparticles in 3.13 µm resolution for 2D and 3D view with current passing over the probe with the scanning area of 9.842 pm2. The XRD result concludes the average size of Cr2O3 nanoparticles as 24.7205 nm. The antioxidant study shows the fluctuation in percentage of antioxidant activity as the concentration varies. The antibacterial activity explains clearly that the prepared sample has zone inhibition with the 3 pathogens studied. Thus the honey medicated nanoparticle synthesis provides a simple, cost effective, reproducible, rapid, and safe method with numerous applications.

Macular edema secondary to retinal vein occlusion in a real-life setting: a multicenter, nationwide, 3-year follow-up study.

To evaluate the presence of macular edema secondary to retinal vein occlusion (RVO)-both central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO)-3 years after diagnosis in patients who underwent intravitreal therapy and to identify potential prognostic factors and biomarkers of persistent macular edema. National multicenter, observational, exploratory, retrospective cohort study of 104 consecutive patients with macular edema secondary to RVO diagnosed from January 2014 to December 2015 with minimum 3-year follow-up time. Data analyzed included best-corrected visual acuity (BCVA), clinical and demographic data, and spectral domain optical coherence tomography parameters. At final observation, median baseline central retinal thickness significantly improved from baseline 538 to 290 μm (p < 0.001) and complete macular edema resolution was achieved in 51.0% of patients (56.3% and 42.5% in BRVO and CRVO patients, respectively). BCVA also improved (p < 0.01). Logistic regression analysis revealed a relationship between recurrence of macular edema and disorganization of retinal inner layers (DRIL) at baseline (odds ratio = 2.88; p = 0.013). Good long-term anatomical and functional outcomes are achieved with intravitreal treatments in RVO patients. Anatomical success and visual gains seen in the first year were maintained throughout the entire follow-up, though DRIL is a major risk factor for recurrence.

Significant structural evolution of a long‐term fallow soil in response to agricultural management practices requires at least 10 years after conversion

AbstractAgricultural practices can have significant effects on the physical and biological properties of soil. The aim of this study was to understand how the physical structure of a compromised soil, arising from long‐term bare‐fallow management, was modified by adopting different field management practices. We hypothesized that changing agricultural practices from bare‐fallow to arable or grassland would influence the modification of pore structure via an increase in porosity and pore connectivity, and a more homogenous distribution of pore sizes, and that this change exerts a rapid evolution of soil structure following conversion. Soil aggregates (&lt;2 mm) collected in successive years from field plots subjected to three contrasting managements were studied: bare‐fallow, bare‐fallow converted to arable, and bare‐fallow converted to grassland. Soil structure was assessed by X‐ray computed tomography on the aggregates at 1.5 μm resolution, capturing detail relevant to soil biophysical processes. The grassland system increased porosity, diversity of pore sizes, pore connectivity and pore‐surface density significantly over the decade following conversion. However, measured at this resolution, the evolution of most of these metrics of soil structure required approximately 10 years post‐conversion to show a significant effect. The arable system did not influence soil structural evolution significantly. Only pore size distribution was modified in grassland in a shorter time frame (2 years post‐conversion). Hence, evolution of soil structural characteristics appears to require at least a decadal timescale following conversion to grassland.Highlights The physical structure of a compromised soil was modified by adopting plant‐based field management practices. Conversion to grassland increased pore size diversity after 2 years. Porosity, pore connectivity and pore surface density showed a significant modification between 7 and 10 years after conversion.

A micrometer-scale snapshot on phototroph spatial distributions: mass spectrometry imaging of microbial mats in Octopus Spring, Yellowstone National Park.

Microbial mats from alkaline hot springs in the Yellowstone National Park are ideal natural laboratories to study photosynthetic life under extreme conditions, as well as the nuanced interactions of oxygenic and anoxygenic phototrophs. They represent distinctive examples of chlorophototroph (i.e., chlorophyll or bacteriochlorophyll-based phototroph) diversity, and several novel phototrophs have been first described in these systems, all confined in space, coexisting and competing for niches defined by parameters such as light, oxygen, or temperature. In a novel approach, we employed mass spectrometry imaging of chloropigments, quinones, and intact polar lipids (IPLs) to describe the spatial distribution of different groups of chlorophototrophs along the~1cm thick microbial mat at 75µm resolution and in the top~1.5mm green part of the mat at 25µm resolution. We observed a fine-tuned sequence of oxygenic and anoxygenic chlorophototrophs with distinctive biomarker signatures populating the microbial mat. The transition of oxic to anoxic conditions is characterized by an accumulation of biomarkers indicative of anoxygenic phototrophy. It is also identified as a clear boundary for different species and ecotypes, which adjust their biomarker inventory, particularly the interplay of quinones and chloropigments, to prevailing conditions. Colocalization of the different biomarker groups led to the identification of characteristic IPL signatures and indicates that glycosidic diether glycerolipids are diagnostic for anoxygenic phototrophs in this mat system. The zoom-in into the upper green part further reveals how oxygenic and anoxygenic phototrophs share this microenvironment and informs on subtle, microscale adjustments in lipid composition of Synechococcus spp.

Retrieval of lower-order moments of the drop size distribution using CSU-CHILL X-band polarimetric radar: a case study

Abstract. The lower-order moments of the drop size distribution (DSD) have generally been considered difficult to retrieve accurately from polarimetric radar data because these data are related to higher-order moments. For example, the 4.6th moment is associated with a specific differential phase and the 6th moment with reflectivity and ratio of high-order moments with differential reflectivity. Thus, conventionally, the emphasis has been to estimate rain rate (3.67th moment) or parameters of the exponential or gamma distribution for the DSD. Many double-moment “bulk” microphysical schemes predict the total number concentration (the 0th moment of the DSD, or M0) and the mixing ratio (or equivalently, the 3rd moment M3). Thus, it is difficult to compare the model outputs directly with polarimetric radar observations or, given the model outputs, forward model the radar observables. This article describes the use of double-moment normalization of DSDs and the resulting stable intrinsic shape that can be fitted by the generalized gamma (G-G) distribution. The two reference moments are M3 and M6, which are shown to be retrievable using the X-band radar reflectivity, differential reflectivity, and specific attenuation (from the iterative correction of measured reflectivity Zh using the total Φdp constraint, i.e., the iterative ZPHI method). Along with the climatological shape parameters of the G-G fit to the scaled/normalized DSDs, the lower-order moments are then retrieved more accurately than possible hitherto. The importance of measuring the complete DSD from 0.1 mm onwards is emphasized using, in our case, an optical array probe with 50 µm resolution collocated with a two-dimensional video disdrometer with about 170 µm resolution. This avoids small drop truncation and hence the accurate calculation of lower-order moments. A case study of a complex multi-cell storm which traversed an instrumented site near the CSU-CHILL radar is described for which the moments were retrieved from radar and compared with directly computed moments from the complete spectrum measurements using the aforementioned two disdrometers. Our detailed validation analysis of the radar-retrieved moments showed relative bias of the moments M0 through M2 was &lt;15 % in magnitude, with Pearson’s correlation coefficient &gt;0.9. Both radar measurement and parameterization errors were estimated rigorously. We show that the temporal variation of the radar-retrieved mass-weighted mean diameter with M0 resulted in coherent “time tracks” that can potentially lead to studies of precipitation evolution that have not been possible so far.

Disentangling dark and luminous phases of nanosecond discharges developing in liquid water

There is no clear experimental evidence of the underlying microscopic physical mechanisms of micro-discharges directly produced in liquids. In this study, we examine shadowgraph images and plasma-induced emission (PIE) to decouple simultaneously developing dark and luminous phases of micro-discharges with nanosecond durations in liquid water. We apply diagnostics with extremely high temporal (down to 30 ps) and spatial (down to 1 μm) resolutions to capture tiny bush-like dark filaments that expand from the anode tip together with the formation of luminous tree-like structures. For the first time, we disentangle two closely coupled dark and luminous phases of the discharge events and determine their onsets accurately with respect to the driving high-voltage (HV) pulse. The dark filaments start appearing within ∼3–4 ns after the onset of the HV pulse, and subsequently expand at a constant velocity of ∼1 × 105–2 × 105 m s−1, depending on the HV amplitude and anode curvature. A systematic analysis of the PIE waveforms using the associated shadowgraph images reveals that the onset of the luminous discharge phase is delayed by ∼600–800 ps with respect to the onset of the initial dark filament structures. Considering the constant propagation velocity of dark filaments, the luminous phase starts to develop when the extension of regions with a perturbed refractive index (i.e., perturbed density) reaches several tens of micrometres. An analysis of PIE tracks within the captured shadowgraph images confirms that luminous filaments develop only in regions affected by primary dark filaments and their attachment to the anode surface coincides with points of initial onset of the first dark filaments. Furthermore, the emission intensity produced during the luminous phase originates from the luminous filaments developing in the bulk liquid. Our study provides an important insight into the dynamics of different phases of micro-discharges in de-ionised water.

Synchrotron X-ray fluorescence imaging of strontium incorporated into the enamel and dentine of wild-shot orangutan canine teeth

ObjectivesDental hard tissues contain trace elements of both dietary and environmental origin. One objective was to demonstrate that a longitudinal record of synchronous Sr incorporation into enamel and dentine can be retrieved from museum specimens of once-free-living endangered species. Further objectives were to quantify sudden fluctuations in Sr concentration and estimate the extent of Sr overprinting back into dentine and enamel formed prior to the time of Sr ingestion. Materials and methodsDaily incremental markings were used to determine rates and times of tooth formation and synchrotron X-ray fluorescence of the same polished ground sections to image Sr distribution in a male and a female orangutan canine. The X-ray beam was monochromatised to 17.0 keV and focused to 500 × 500 nm2. Scans were performed at either 25.0 or 5.0 μm resolution. ResultsBaseline Sr levels ranged between 215-750 ppm. Multiple short, intense Sr labels reaching 750- 1,625 ppm occurred randomly throughout 15-22 years of tooth formation. In dentine, Sr concentration increased gradually away from the EDJ, while in enamel, it reduced towards the enamel surface. Using daily incremental markings, Sr overprinting into earlier formed dentine and enamel was estimated to be ∼12-45 days. There was no evidence of Sr overprinting by maturational ameloblasts. ConclusionsA good record of growth and trace element incorporation into tooth tissues can be retrieved from museum specimens. Short, intense Sr labels were equally well time-resolved in enamel and dentine and could be distinguished from more diffuse background levels. Enamel maturation appears to have no quantifiable effect.

Quantitative X-ray µCT Measurement of the Effect of Ore Characteristics on Non-Surface Mineral Grain Leaching

In heap (bio)leaching processes, a substantial fraction of the valuable mineral is positioned below the ore particle surface. X-ray micro-computed tomography (μCT) was used to quantify the effect of ore type and structure and operating temperature on the leaching of this mineral, to investigate the rate-controlling factors. Mini-leaching columns containing agglomerated chalcopyrite, pyrite, and malachite ores were scanned by X-ray μCT (13.40 µm resolution) at select time intervals. The leaching of a relatively porous malachite ore was reaction-controlled, with no leaching penetration limitation into the ore particles. For two less porous ore types, the structure and higher porosity of the agglomerate rim and conditions that resulted in the degradation of the full ore matrix structure were found to be the determining variables of the leaching extent and time. In the case of a chalcopyrite ore, an enhancement of copper recovery and sulphide mineral dissolution with increasing temperature was attributable to the increased leaching penetration distance and crack development in addition to thermodynamically expected increased leaching rate. Increasing temperature did not affect the maximum penetration distance for the waste rock containing pyrite, with no crack development observed. Overall increases in iron recovery were due to accelerated leaching rates, though diffusion or mineral access limitations were evident at a higher temperature.

Manufacturing conductive patterns on polymeric substrates: development of a microcontact printing process

The integration of high-resolution conductive structures into polymer devices using a low-cost, rapid, and accurate manufacturing technique is important for the future of the microfluidic, photovoltaic, flexible printing, and organic electronics industries. In this study, the microcontact printing (μCP) of high-resolution conductive patterns on polymer substrates using silver nanoparticle inks and a roll-based printing equipment was empirically investigated. A process model was developed to predict the quality of the printed patterns (defined as thickness and coverage ratio) from known printing parameters, based on the statistical analysis of a set of carefully designed experiments that were informed by theoretical understanding of the μCP process. The statistically relevant variables in the process model for the pattern thickness were ink solids loading, ink viscosity, stamp feature size, and the surface energy ratio of ink to substrate. For the coverage model, the key inputs were ink solids loading, ink viscosity, stamp feature size, and inkpad thickness. The effects of these variables on the thickness and coverage of the printed patterns were quantified by a linear model derived from an orthogonal, fractional factorial experimental design with five input factors and two outputs. The extension of the process model to predict the printing behavior of other inks and substrates, and the successful printing of conductive features on polymer substrates with 5 μm resolution, were demonstrated.

An Inductive Linear Displacement Sensor With Bilateral Sensing Units

This paper presents an inductive linear displacement sensor with bilateral sensing units, which consists of a stator with excitation coils, two movers with pickup coils and a mover base. Two movers have the same structure and work on two sides of the stator to realize bilateral sensing. Bilateral sensing units contribute to reducing the negative influence from the gap change between the movers and stator on the measurement performance of the sensor, because bilateral mover structure is able to maintain the sum of two side gaps constant and thus reach good magnetic coupling with the stator. Comparison experiments of the prototypes in different working gaps have been implemented and verified that the sensor with bilateral sensing units has better repeatability and accuracy than that with unilateral sensing unit. Based on the regular errors shown in the measurement results of the proposed bilateral sensing sensor in comparison experiments, this paper also presents the detailed analysis about the sources of some dominating error components. Accordingly, a sensor prototype with improved designs for reducing measurement errors was developed. Final experimental results of the improved sensor prototype show that the accuracy is better than 15μm and the repeatability is about 7μm with less than 1.2μm resolution in the range of 0mm~288mm.

15‐4: New Gen. 6 Exposure Tools for 1.2 μm Resolution

At Display Week 2019, we presented design concepts of new exposure tools with DUV and exposure results by a 6‐inch‐field test tool. This paper reports resolution performance of the new Gen.6 exposure tools. Latest exposure results of 1.2 μm L&amp;S and 1.8 μm hole by the Gen.6 tool are presented.

High‐Sensitivity Moment Magnetometry With the Quantum Diamond Microscope

AbstractInterest in magnetic fields on the ancient Earth and other planetary bodies has motivated the paleomagnetic analysis of complex rocks such as meteorites that carry heterogeneous magnetizations at &lt;&lt;1 mm scales. The net magnetic moment of natural remanent magnetization (NRM) in such small samples is often below the detection threshold of common cryogenic magnetometers. The quantum diamond microscope (QDM) is an emerging magnetic imaging technology with ~1 μm resolution and can, in principle, recover magnetizations as weak as 10−17 Am2. However, the typically 1–100 μm sample‐to‐sensor distance of QDM measurements can result in complex (nondipolar) magnetic field maps, from which the net magnetic moment cannot be determined using a simple algorithm. Here we generate synthetic magnetic field maps to quantify the errors introduced by sample nondipolarity and by map processing procedures such as upward continuation. We find that inversions based on least squares dipole fits of upward continued data can recover the net moment of complex samples with &lt;5% to 10% error for maps with signal‐to‐noise ratio (SNR) in the range typical of current generation QDMs. We validate these error estimates experimentally using comparisons between QDM maps and between QDM and SQUID microscope data, concluding that, within the limitations described here, the QDM is a robust technique for recovering the net magnetic moment of weakly magnetized samples. More sophisticated net moment fitting algorithms in the future can be combined with upward continuation methods described here to improve accuracy.

A MEMS lens scanner based on serpentine electrothermal bimorph actuators for large axial tuning.

Confocal microscopes and two-photon microscopes are powerful tools for early cancer diagnosis because of their high-resolution 3D imaging capability, but applying them for clinical use in internal organs is hindered by the lack of axially tunable lens modules with small size, high image quality and large tuning range. This paper reports a compact MEMS lens scanner that has the potential to overcome this limitation. The MEMS lens scanner consists of a MEMS microstage and a microlens. The MEMS microstage is based on a unique serpentine inverted-series-connected (ISC) electrothermal bimorph actuator design. The microlens is an aspheric glass lens to ensure optical quality. The MEMS microstage has been fabricated and the lens scanner has been successfully assembled. The entire lens scanner is circular with an outer diameter of 4.4 mm and a clear optical aperture of 1.8 mm. Experiments show that the tunable range reaches over 200 µm at only 10.5 V and the stiffness of the microstage is 6.2 N/m. Depth scan imaging by the MEMS lens scanner has also been demonstrated with a 2.2 µm resolution, only limited by the available resolution target.

Micro-computed tomography evaluation of root canal filling quality with apical negative pressure

ObjectivesThe objective of the present study was to compare, using micro-computed tomography (micro-CT), the location and volume percentage of voids in root canals that were obturated with a premixed tricalcium silicate sealer and a single gutta-percha master cone, in the presence or absence of apical negative pressure. MethodsTwenty extracted human mandibular premolars were cleaned and shaped. The teeth were assigned to 2 groups (n = 10) according to the filling technique: apical negative pressure sealer application combined with the single-cone technique (NPS) or syringe-assisted sealer application combined with the single-cone technique (SS). Each specimen was scanned using micro-CT at 10 μm resolution. The percentages of voids were calculated from segmental regions of interest. Data were analysed using nonparametric statistical methods, with statistical significance pre-set at α = 0.05. ResultsSignificant difference was identified (p < 0.05) in the overall percentage of voids between the NPS group (0.33 %; interquartile range 0.25 %) and the SS group (6.29 %; interquartile range 5.57 %). In the NPS group, the percentages of voids in the coronal-third or middle-third of the canal space were statistically lower than that in apical-third (p < 0.0167, Bonferroni adjustment), with no significant difference between the former two groups. In the SS group, no significant difference in the percentages of voids was identified among the coronal-third, middle-third and apical-third of the canal space. ConclusionsApical negative pressure sealer application combined with the single-cone technique produces fewer voids in root canal fillings than the conventional single-cone technique. Clinical significanceThe apical negative pressure sealer application technique combined with single-cone filling constitutes a novel root canal obturation technique that improves the quality of root canal filling by minimising the volume of voids within the three-dimensional canal space.

Printable highly transparent natural fiber composites

In this study, we report the development of printable highly transparent natural fiber-reinforced composites based on raw flax fibers. The prepared composites exhibit superior transparency (>90% light transmittance), and the tensile performance is competitive to synthetic fiber-based counterparts. They also reveal excellent printability (<300 µm resolution) in additive manufacturing (AM) processes, allowing the fabrication of functional devices in multiplex geometries using plant-based materials. The findings indicate a novel and sustainable method to engineer transparent composites with excellent mechanical and processing characteristics.

Fiber directional position sensor based on multimode interference imaging and machine learning.

A fiber directional position sensor based on multimode interference and image processing by machine learning is presented. Upon single-mode injection, light in multimode fiber generates a multi-ring-shaped interference pattern at the end facet, which is susceptible to the amplitude and direction of the fiber distortions. The fiber is mounted on an automatic translation stage, with repeating movement in four directions. The images are captured from an infrared camera and fed to a machine-learning program to train, validate, and test the fiber conditions. As a result, accuracy over 97% is achieved in recognizing fiber positions in these four directions, each with 10 classes, totaling an 8 mm span. The number of images taken for each class is merely 320. Detailed investigation reveals that the system can achieve over 60% accuracy in recognizing positions on a 5 µm resolution with a larger dataset, approaching the limit of the chosen translation stage.

Fabrication of Paper-based Microfluidic Devices Using a Laser Beam Scanning Technique.

This paper describes a novel method for fabricating paper-based microfluidic devices using a laser beam scanning technique. Cellulose chromatography papers were treated with octadecyltrichlorosilane (OTS) to make them entirely hydrophobic. A photoacid generator (CPI-410S) was soaked into the paper, and irradiated with a 405-nm laser beam to induce acid generating reactions. Since the silyl ether bond between cellulose and OTS was cleaved by the hydrolysis reaction, the photo-irradiated area changed to hydrophilic. By scanning the laser beam using a Galvo mirror system, arbitrary shaped hydrophilic patterns were successfully created on the paper in 50 μm resolution. To the best of our knowledge, this is the first report on the fabrication of hydrophilic channels on the OTS-treated paper using photo-induced acid generation processes coupled with the laser beam scanning technique. Quantification of nitrite was demonstrated with the paper device made by this method.

Evidence of radial Weibel instability in relativistic intensity laser-plasma interactions inside a sub-micron thick liquid target

Super-intense laser plasma interaction has shown great promise as a platform for next generation particle accelerators and sources for electron, x-rays, ions and neutrons. In particular, when a relativistic intense laser focus interacts with a thin solid density target, ionized electrons are accelerated to near the speed of light (c) within an optical cycle and are pushed in the forward and transverse directions away from focus, carrying a significant portion of the laser energy. These relativistic electrons are effectively collisionless, and their interactions with the ions and surrounding cold electrons are predominantly mediated by collective electromagnetic effects of the resulting currents and charge separation. Thus, a deeper understanding of subsequent high energy ions generated from various mechanisms and their optimization requires knowledge of the relativistic electron dynamics and the fields they produce. In addition to producing MV/m quasi-static fields, accelerating the ions and confining the majority of the electrons near the bulk of the laser target, these relativistic electron currents are subject to plasma instabilities like the Weibel instability as they propagate through the thermal population in the bulk target. In this work, we present high temporal (100 fs) and spatial (1 μm) resolution shadowgraphy video capturing relativistic radial ionization front expansion and the appearance of filamentation radiating from the laser spot within a sub-micron thick liquid sheet target. Filamentation within the region persists for several picoseconds and seeds the eventual recombination and heating dynamics on the nanosecond timescale. A large scale three-dimensional particle-in-cell (PIC) simulation of the interaction revealed the presence of strong magnetic fields characteristic of Weibel Instability, and corroborated the relativistic radial expansion of the ionization front, whose speed was determined to be 0.77c. Both the experimental and simulation results strongly point towards the target field ionization and the outward expanding hot electron current as the cause of the radial expansion.