Μm Radius Research Articles

Compact titanium dioxide waveguides with high nonlinearity at telecommunication wavelengths.

Dense integration of photonic integrated circuits demands waveguides simultaneously fulfilling requirements on compactness, low loss, high nonlinearity, and capabilities for mass production. In this work, titanium dioxide waveguides with a thick core of 380 nm exhibiting a compact mode size (0.43 μm2) and a low loss (5.4 ± 1 dB/cm) at telecommunication wavelengths around 1550 nm have been fabricated and measured. A microring resonator having a 50 μm radius has been measured to have a loaded quality factor of 53500. Four-wave mixing experiments reveal a nonlinear parameter for the waveguides of 21-34 W-1 m-1 corresponding to a nonlinear index around 2.3-3.6 x 10-18 m2/W, which results in a wavelength conversion efficiency of -36.2 dB. These performances, together with the potentially simple dispersion engineering to the fabricated waveguides by the post processes, yield a strong promise for the titanium dioxide waveguides applied in photonic integrated circuits, especially for nonlinear implementations.

Microfluidic High-Q Circular Substrate-Integrated Waveguide (SIW) Cavity for Radio Frequency (RF) Chemical Liquid Sensing.

In this study, a high-Q circular substrate-integrated waveguide (SIW) cavity resonator is proposed as a non-contact and non-invasive radio frequency (RF) sensor for chemical sensing applications. The design of the structure utilizes SIW technology along with a circular shape to achieve a high unloaded Q factor, which is one of the important requirements for RF sensors. The resonant frequency of the proposed circular SIW cavity sensor changes when a liquid material or a chemical (microliters) is inserted in the sensitive area of the structure. The sensing of liquid materials with different permittivities is accomplished via the perturbation of the electric fields in the SIW configuration. When a microwell that is 4 mm in radius is installed vertically through the center of the bare circular SIW cavity, the operating frequency varies from 5.26 to 5.34 GHz. Similarly, when the microwell contains ethanol, the frequency shifts from 5.26 to 5.18 GHz, and the amplitude of reflection coefficient is shifted from −29 dB to −17 dB; when the microwell contains mixing deionized (DI)-water, the frequency moves from 5.26 to 4.98 GHz (which is also 0% Ethanol in our study), and the amplitude of reflection coefficient is shifted from −29 dB to −8 dB. A high unloaded Q factor is maintained throughout all experimental results. To demonstrate our idea, different concentrations of ethanol are tested and recorded. The experimental validation yields a close agreement between the simulations and the measurements.

Magnetically assisted intraperitoneal drug delivery for cancer chemotherapy

Intraperitoneal (IP) chemotherapy has revived hopes during the past few years for the management of peritoneal disseminations of digestive and gynecological cancers. Nevertheless, a poor drug penetration is one key drawback of IP chemotherapy since peritoneal neoplasms are notoriously resistant to drug penetration. Recent preclinical studies have focused on targeting the aberrant tumor microenvironment to improve intratumoral drug transport. However, tumor stroma targeting therapies have limited therapeutic windows and show variable outcomes across different cohort of patients. Therefore, the development of new strategies for improving the efficacy of IP chemotherapy is a certain need. In this work, we propose a new magnetically assisted strategy to elevate drug penetration into peritoneal tumor nodules and improve IP chemotherapy. A computational model was developed to assess the feasibility and predictability of the proposed active drug delivery method. The key tumor pathophysiology, including a spatially heterogeneous construct of leaky vasculature, nonfunctional lymphatics, and dense extracellular matrix (ECM), was reconstructed in silico. The transport of intraperitoneally injected magnetic nanoparticles (MNPs) inside tumors was simulated and compared with the transport of free cytotoxic agents. Our results on magnetically assisted delivery showed an order of magnitude increase in the final intratumoral concentration of drug-coated MNPs with respect to free cytotoxic agents. The intermediate MNPs with the radius range of 200–300 nm yield optimal magnetic drug targeting (MDT) performance in 5–10 mm tumors while the MDT performance remains essentially the same over a large particle radius range of 100–500 nm for a 1 mm radius small tumor. The success of MDT in larger tumors (5–10 mm in radius) was found to be markedly dependent on the choice of magnet strength and tumor-magnet distance while these two parameters were less of a concern in small tumors. We also validated in silico results against experimental results related to tumor interstitial hypertension, conventional IP chemoperfusion, and magnetically actuated movement of MNPs in excised tissue.

A study on the performance of an electrostatic focusing mirror for Rydberg positronium

Recently, we demonstrated an electrostatic mirror that focuses a beam of Rydberg positronium atoms over a 6 m path to a 32 ± 1 mm FWHM diameter spot on a position sensitive detector. The mirror is comprised of 360 wires arranged in the shape of a nearly-cylindrical revolved truncated ellipse ~96 mm in radius, with potentials of equal and opposite magnitude applied to alternating wires to create a short-ranged electric field that decreases in magnitude exponentially with e-folding length = 0.53 mm. Here, we explore in detail the observed resolution and discuss the factors contributing to its broadening from the ideal point focus of a perfect embodiment of the mirror. Improvements to the design are considered, with the aim to achieve a mirror with a resolution of <0.5 mm, which is necessary for a proposed measurement of the gravitational deflection of positronium.

Spatial-Temporal Cellular Bioeffects from Acoustic Droplet Vaporization.

One of the major challenges in developing acoustic droplet vaporization (ADV)-associated therapy as an effective and safe strategy is the precise determination of the spatial cellular bioeffects after ADV (cell death or cell membrane permeabilization). In this study, we combined high-speed camera imaging and live-cell microscopic imaging to observe the transient dynamics of droplets during ADV and to evaluate the mechanical force on cells.Methods: C6 glioma cells were co-incubated with DiI-labeled droplets (radius: 1.5, 2.25, and 3.0 μm). We used an acousto-optical system for high-speed bright-field (500 kfps) and fluorescence (40 kfps) microscopic imaging in order to visualize the dynamics of droplets under ultrasound excitation (frequency = 5 MHz, pressure = 5-8 MPa, cycle number = 3, pulse number = 1). Live-cell microscopic imaging was used to monitor the cell morphology, cell membrane permeabilization, and cell viability by membrane-anchored Lyn-yellow fluorescence protein, propidium Iodide staining, and calcein blue AM staining, respectively.Results: We discovered that the spatial distribution of ADV-induced bioeffects could be mapped to the physical dynamics of droplet vaporization. For droplets with a 1.5 μm radius, the distance threshold for ADV-induced cell death (5.5±1.9 μm) and reversible membrane permeabilization (11.3±3.5 μm) was well correlated with the distance of ADV-bubble pressing downward to the floor (5.7±1.3 μm) and maximum distance of droplet expansion (11.5±2.6 μm), respectively. These distances were enlarged by increasing the droplet sizes and insonation acoustic pressures. The live-cell imaging results show that ADV-bubbles can directly disrupt the cell membrane layer and induce intensive intracellular substance leakage. Further, the droplets shed the payload onto nearby cells during ADV, suggesting ADV could directly induce adjacent cell death by physical force and enhancement of chemotherapy to distant cells.Conclusion: This study provide new insights into the ADV-mediated physicochemical synergic effect for medical applications.

Analysis of interfacial joint strength of microwave and conventionally brazed alumina ceramic joints using scratch test method

The present investigation demonstrated the comparative studies on interfacial joint strength of the alumina-alumina joints fabricated by conventional and microwave-assisted brazing techniques using scratch test method. Scratch tests were performed on cross-sectional surfaces of the alumina joints under steadily increasing normal loads up to 140 N. The scratches were made with a Rockwell C hardness tester stylus with 200 µm radius. The response of the joints was investigated by measuring the fluctuations in the tangential force during scratch test as well as by the examination of the scratch tracks. It was observed that microwave brazed joint had better interfacial joint strength in comparison to the conventionally brazed joint.

A study on the machining accuracy of dental digital method focusing on dental inlay.

PURPOSEThe purpose of this study was to compare the cutting method and the lamination method to investigate whether the CAD data of the proposed inlay shape are machined correctly.MATERIALS AND METHODSThe Mesial-Occlusal shape of the inlay was modeled by changing the stereolithography (STL). Each group used SLS (metal powder) or SLA (photocurable resin) in the additive method, and wax or zirconia in the subtractive method (n=10 per group, total n=40). Three-dimensional (3D) analysis program (Geomagic Control X inspection software; 3D systems) was used for the alignment and analysis. The root mean square (RMS) in the 2D plane state was measured within 50 µm radius of eight comparison measuring points (CMP). Differences were analyzed using one-way analysis of variance and post-hoc Tukey's test were used (α=.05).RESULTSThere was a significant difference in RMS only in SLA and SLS of 2D section (P<.05). In CMP mean, CMP 4 (−5.3±46.7 µm) had a value closest to 0, while CMP 6 (20.1±42.4 µm) and CMP 1 (−89.2±61.4 µm) had the greatest positive value and the greatest negative value, respectively.CONCLUSIONSince the errors obtained from the study do not exceed the clinically acceptable values, the lamination method and the cutting method can be used clinically.

Ultra-precision machining of grayscale pixelated micro images on metal surface

In this paper, a novel machining technique, diamond micro lithography (DML), is developed to provide a possible solution to generate grayscale micro images on metal surfaces. This technique is capable of converting a grayscale image into a pixelated array of customized micro features. The micro feature cell is designed to be a micro inverted pyramid structure as the constituent pixel, which can be engraved by a V-shape sharp diamond tool using a multi-axis ultra-precision machine. Based on an assumption that the perceived luminance by the observer is directly related with the size and geometry of the respective pyramid structure machined, the cell size of each micro feature is designed to have a value linearly related with the grayness value of the corresponding pixel. The distribution of feature-based pixels is determined by superimposed projection algorithm, a customized image processing technique developed in this study to convert the grayscale image to CNC machining codes. A series of machining tests are conducted to evaluate the effect of cell aperture size and cell aspect ratio on the grayness of pixels as well as to prove the assumption made on the relationship between cell geometry and pixel grayness. To explore the performance of DML, the size of machined grayscale image on metal surface is continuously scaled down from 2 mm to 100 μm radius, which is still able to be recognized with the aid of a microscope, demonstrating the capability of DML in transferring pixelated image on metal surface with high fidelity and intelligibility in a wide range of image size. The machined metal workpiece has the potential to be used as mold to replicate the vivid grayscale images onto polymer products for anti-counterfeiting purpose.

Effect of Glucose on the Mobility of Membrane-Adhering Liposomes.

Enclosed lipid bilayer structures, referred to as liposomes or lipid vesicles, have a wide range of biological functions, such as cellular signaling and membrane trafficking. The efficiency of cellular uptake of liposomes, a key step in many of these functions, is strongly dependent on the contact area between a liposome and a cell membrane, which is governed by the adhesion force w, the membrane bending energy κ, and the osmotic pressure Δp. Herein, we investigate the relationship between these forces and the physicochemical properties of the solvent, namely, the presence of glucose (a nonionic osmolyte). Using fluorescence microscopy, we measure the diffusivity D of small (∼50 nm radius), fluorescently labeled liposomes adhering to a supported lipid bilayer or to the freestanding membrane of a giant (∼10 μm radius) liposome. It is observed that glucose in solution reduces D on the supported membrane, while having negligible effect on D on the freestanding membrane. Using well-known hydrodynamic theory for the diffusivity of membrane inclusions, these observations suggest that glucose enhances the contact area between the small liposomes and the underlying membrane, while not affecting the viscosity of the underlying membrane. In addition, quartz crystal microbalance experiments showed no significant change in the hydrodynamic height of the adsorbed liposomes, upon adding glucose. This observation suggests that instead of osmotic deflation, glucose enhances the contact area via adhesion forces, presumably due to the depletion of the glucose molecules from the intermembrane hydration layer.

Influence of indenter geometry on the frictional sliding resistance of tooth enamel

Abstract Indentation force-displacement and sliding scratch resistance measurements have been conducted on orangutan tooth enamel. Tests were made with a corner-cube (CC), Berkovich, as well as spherical (nominally 1 μm and 5 μm radius) indenters. Indentation loads ranged from 100 to 5000 μN and were also made on fused silica to calibrate the indenter tips. The frictional force as a function of sliding distance was measured with the atomic force microscope (AFM) option on the indenter system as well as using a high precision AFM and scanning electron microscope (SEM). The frictional resistance was found to be almost constant with indenter load for the CC and Berkovich indenters; for the CC, it depended upon the orientation of the sliding indenter. For the spherical indenters, the 1 μm showed a sharp increase in frictional resistance with increasing load whereas for the 5 μm tip there was minimal change. Observations of the resultant scratches showed ploughing/cutting with the sharp indenters and a transition from an “ironing” like deformation for all the 5 μm tests and for the low load 1 μm tip with ploughing at the heaviest load. In the case of the sharp tips a “metallic” like discontinuous swarf removal process was evident. It was found that the frictional resistance force scaled with the effective rake angle of the indenter tips. Implications of the current observations for understanding tooth wear are considered.

Insight into the Pore Structure of Tight Gas Sandstones: A Case Study in the Ordos Basin, NW China

A wide spectrum of pore size distributions (PSD) exists in tight gas sandstones, ranging from several nanometers to several hundred micrometers in radius, which controls both the physical rock-flow capacity and storage capacity. Thin-section, scanning electron microscope (SEM), field emission scanning electron microscope (FE-SEM), high-pressure mercury intrusion (HPMI), constant-rate mercury intrusion (CRMI) and micro-CT scanning experiments are performed on tight sandstone samples from the eighth member of the Middle Permian Shihezi Formation (P2h8) in the Ordos Basin to better understand the pore-system characteristics of a tight gas sandstone. The results of this case study show that various types of pores exist in the P2h8 sandstones: residual intergranular pores, intraparticle dissolution pores, intercrystalline pores, and small micro-cracks are observed. We combine HPMI and CRMI to determine the PSD; the pore sizes range from 3.7 nm to 600 μm in radius. The multimodal PSD is characterized by two bro...

Model of Intraperitoneal Targeted α-Particle Therapy Shows That Posttherapy Cold-Antibody Boost Enhances Microtumor Radiation Dose and Treatable Tumor Sizes.

Intraperitoneally administered radiolabeled monoclonal antibodies (mAbs) have been tested in several clinical trials, often with promising results, but have never proven curative. Methods: We have previously presented simulations of clinically relevant amounts of intraperitoneal 90Y-mAbs for treatment of minimal disease and shown that such treatments are unlikely to eradicate microtumors. Our previous model simulated the kinetics of intraperitoneally infused radiolabeled mAbs in humans and showed the benefit of instead using α-emitters such as 211At. In the current work, we introduce penetration of mAbs into microtumors with radii of up to 400 μm. Calculations were performed using dynamic simulation software. To determine the radiation dose distribution in nonvascularized microtumors of various sizes after intraperitoneal 211At-radioimmunotherapy, we used an in-house-developed Monte Carlo program for microdosimetry. Our aim was to find methods that optimize the therapy for as wide a tumor size range as possible. Results: Our results show that high-specific-activity radiolabeled mAbs that are bound to a tumor surface will penetrate slowly compared with the half-lives of 211At and shorter-lived radionuclides. The inner-core cells of tumors with radii exceeding 100 μm may therefore not be sufficiently irradiated. For lower specific activities, the penetration rate and dose distribution will be more favorable for such tumors, but the dose to smaller microtumors and single cells will be low. Conclusion: Our calculations show that the addition of a boost with unlabeled mAb 1-5 h after therapy results in sufficient absorbed doses both to single cells and throughout microtumors up to approximately 300 μm in radius. This finding should also hold for other high-affinity mAbs and short-lived α-emitters.

Effects of Endwall Fillet and Bulb on the Temperature Uniformity of Pin-Fined Microchannel

Endwall fillet and bulb structures are proposed in this research to improve the temperature uniformity of pin-fined microchannels. The periodical laminar flow and heat transfer performances are investigated under different Reynolds numbers and radius of fillet and bulb. The results show that at a low Reynolds number, both the fillet and the bulb structures strengthen the span-wise and the normal secondary flow in the channel, eliminate the high temperature area in the pin-fin, improve the heat transfer performance of the rear of the cylinder, and enhance the thermal uniformity of the pin-fin surface and the outside wall. Compared to traditional pin-fined microchannels, the flow resistance coefficient f of the pin-fined microchannels with fillet, as well as a bulb with a 2 μm or 5 μm radius, does not increase significantly, while, f of the pin-fined microchannels with a 10 μm or 15 μm bulb increases notably. Moreover, Nu has a maximum increase of 16.93% for those with fillet and 20.65% for those with bulb, and the synthetic thermal performance coefficient TP increases by 16.22% at most for those with fillet and 15.67% at most for those with bulb. At last, as the Reynolds number increases, heat transfer improvement of the fillet and bulb decreases.

A tabletop, ultrashort pulse photoneutron source driven by electrons from laser wakefield acceleration

Relativistic electron beams driven by laser wakefield acceleration were utilized to produce ultrashort neutron sources. The experiment was carried out on the 38 fs, ∼0.5 J, 800 nm Ti:Sapphire laser in the 10 TW UT3 laser lab at University of Texas at Austin. The target gas was a high density pulsed gas jet composed of 90% He and 10% N2. The laser pulse with a peak intensity of 1.5 × 1018 W/cm2 interacted with the target to create a cylindrical plasma channel of 60 μm radius (FWHM) and 1.5 mm length (FWHM). Electron beams of ∼80 pC with the Gaussian energy distribution centered at 37 MeV and a width of 30 MeV (FWHM) were produced via laser wakefield acceleration. Neutron fluences of ∼2.4 × 106 per shot with hundreds of ps temporal length were generated through bremsstrahlung and subsequent photoneutron reactions in a 26.6 mm thick tungsten converter. Results were compared with those of simulations using EPOCH and GEANT4, showing agreement in electron spectrum, neutron fluence, neutron angular distribution and conversion rate.

벤더 디스크형 저주파 수중 음향 발생기의 특성분석

We have performed characteristic analysis on developed bender-disc type underwater sound projector which is used for producing low frequency and high power sound source. The circular unit bender- disc is 60 mm in radius and 27 mm in hight and both sides of the unit disc are radiating surfaces which vibrate in flexural mode of unimorph bender disc. The thickness and radius of piezoelectric layers of the bender disc are 2.5 mm and 60 mm respectively. PZT4 and PZT5A were used for the piezoelectric layer to compare its characteristics. The array projector consists of 12 unit discs which are aligned in a normal direction of the radiating surface with gap size of 13 mm. Transmitting voltage responses (TVR) and source level (SL) of the unit disc was analysed by lumped parameter models and 2d axisymmetric finite element models varying design parameters. The acoustic performance of the projector was experimently evaluated and analyzed on TVR, SL, horizontal beam pattern, and linearity.

Exploring Chemistry in Microcompartments Using Guided Droplet Collisions in a Branched Quadrupole Trap Coupled to a Single Droplet, Paper Spray Mass Spectrometer.

Recent studies suggest that reactions in aqueous microcompartments can occur at significantly different rates than those in the bulk. Most studies have used electrospray to generate a polydisperse source of highly charged microdroplets, leading to multiple confounding factors potentially influencing reaction rates (e.g., evaporation, charge, and size). Thus, the underlying mechanism for the observed enhancement remains unclear. We present a new type of electrodynamic balance-the branched quadrupole trap (BQT)-which can be used to study reactions in microdroplets in a controlled environment. The BQT allows for condensed phase chemical reactions to be initiated by colliding droplets with different reactants and levitating the merged droplet indefinitely. The performance of the BQT is characterized in several ways. Sub-millisecond mixing times as fast as ∼400 μs are measured for low velocity (∼0.1 m/s) collisions of droplets with <40 μm diameters. The reaction of o-phthalaldehyde (OPA) with alanine in the presence of dithiolthreitol is measured using both fluorescence spectroscopy and single droplet paper spray mass spectrometry. The bimolecular rate constant for reaction of alanine with OPA is found to be 84 ± 10 and 67 ± 6 M-1 s-1 in a 30 μm radius droplet and bulk solution, respectively, which demonstrates that bimolecular reaction rate coefficients can be quantified using merged microdroplets and that merged droplets can be used to study rate enhancements due to compartmentalization. Products of the reaction of OPA with alanine are detected in single droplets using paper spray mass spectrometry. We demonstrate that single droplets with <100 pg of analyte can easily be studied using single droplet mass spectrometry.

Region and species dependent mechanical properties of adolescent and young adult brain tissue

Traumatic brain injuries, the leading cause of death and disability in children and young adults, are the result of a rapid acceleration or impact of the head. In recent years, a global effort to better understand the biomechanics of TBI has been undertaken, with many laboratories creating detailed computational models of the head and brain. For these models to produce realistic results they require accurate regional constitutive data for brain tissue. However, there are large differences in the mechanical properties reported in the literature. These differences are likely due to experimental parameters such as specimen age, brain region, species, test protocols, and fiber direction which are often not reported. Furthermore, there is a dearth of reported viscoelastic properties for brain tissue at large-strain and high rates. Mouse, rat, and pig brains are impacted at 10/s to a strain of ~36% using a custom-built micro-indenter with a 125 μm radius. It is shown that the resultant mechanical properties are dependent on specimen-age, species, and region, under identical experimental parameters.

Detection of micron size phantom of biological cell using concentric square ring metamaterial at microwave frequency

ABSTRACTThis paper presents simulation studies and theoretical analysis of sensing property of concentric square ring metamaterial biological materials. Phantom of dielectric cell having dimension 100 µm long and 25 µm in radius is considered. Sensor is designed using periodic arrays of split ring resonators and wires having negative permittivity and permeability at 16.694 GHz. Transmission parameters are extracted using CST MWS software. Change in resonance is observed on placing phantom close to the sensor due to the change in capacitance and inductance. Designed sensor can sense single phantom cell with 133 MHz of shift in resonance. Study shows that sensor has good sensitivity for detecting micron size dielectric objects.

Initiation of basal slip and tensile twinning in magnesium alloys during nanoindentation

The present study addresses the challenge of determining the stress required for the initiation of deformation modes in Mg alloys. Nanoindentation is employed to detect the onset of basal slip and tensile twinning. A Mg-6 wt. % Zn alloy and a series of Mg-Gd binary alloys with concentrations between 0.3 and 4 wt. % Gd are examined in the extruded state. Nanoindentation tests were conducted on {101¯0} and {112¯0} crystal planes using a 5 μm radius spherical indenter. It is shown that the initial yielding point in the load trace corresponds to the appearance of basal slip lines on the sample surface. A pop-in event is seen to accompany the appearance of twinning. We find that the addition of Zn strengthens the basal slip but shows mild influence on twin initiation. For alloying with Gd, an impact on basal slip and twinning is only seen at the highest solute levels. A means of examining the alloying effect on twin growth is proposed and revealed that solute Zn has a greater impact on twin growth than initiation.

Fragment Impacts Into Concrete

Massive concrete withstand blast wave and fragment impacts effectively, and consequently, reinforced concrete is commonly used for protective structures. An important issue is how the fragment impacts influences the concrete. It is well known that the behaviour of concrete exposed to fragment impacts leads to damage in the form of severe cracking as well as spalling. When fragment penetrates concrete deeply, scabbing may occur at the reverse side of the wall, or even perforation. However, the knowledge of how the fragment impacts influences the material properties of concrete are not well known. To study this, experiments have been carried out, in order to examine to what extent the concrete, at various distances, is affected by the fragments. The fragments, which were spherical and 4 mm in radius, were shot against concrete blocks with dimensions of 750 x 750 x 500 mm3 at a speed of approximately 1 650 m/s. The depth of penetration and crater size was measured. Thereafter, the concrete blocks were cut in two halves and the global macro cracking observed. Uniaxial compressive and splitting tests were made from cylinders, which were drilled out from various positions of the block. Furthermore, specimen from the blocks were thin grinded and micro cracking was analyzed with microscope. Experiments presented here shows that the damage from fragment impacts is localized in the very front of the impact zone. The concrete strength below this zone, though, was hardly affected at all. This indicates that is possible to distinguish between the global load effects and the local damage effects, which is caused by the fragment impacts. Consequently, it might be possible to separate the loads from blast wave and fragment impacts, in design; and hence, the structure could be analyzed as a pre-damaged structure with decreased effective depth or width.