Glass Microcapillary Research Articles

Comparison of decarboxylation rates of acidic cannabinoids between secretory cavity contents and air-dried inflorescence extracts in Cannabis sativa cv. ‘Cherry Wine’

Studies with secretory cavity contents and air-dried inflorescence extracts of the CBD-rich hemp strain, Cannabis sativa cv. ‘Cherry Wine’, were conducted to compare the decarboxylation rates of acidic cannabinoids between two groups. The secretory cavity contents acquired from the capitate-stalked glandular trichomes by glass microcapillaries, and inflorescence samples air-dried for 15 days of storage in darkness at room temperature were analysed by high-pressure liquid chromatography. The ratio of acidic cannabinoids to the total cannabinoids was ranging from 0.5% to 2.4% lower in the air-dried inflorescence samples compared to the secretory cavity samples as follows. In the secretory cavity content, the percentage of acidic cannabinoids to the total cannabinoids was measured as 86.4% cannabidiolic acid (CBDA), 6.5% tetrahydrocannabinolic acid (THCA), 4.3% cannabichromenic acid (CBCA), 1.4% cannabigerolic acid (CBGA), and 0.6% cannabidivarinic acid (CBDVA), respectively. In the air-dried inflorescence, however, the acidic cannabinoids were detected with 84% CBDA, 4.8% THCA, 3.3% CBCA, 0.8% CBGA, and 0.3% Δ9-tetrahydrocannabivarinic acid (Δ9-THCVA), respectively. The ratio of cannabidiol (CBD) to cannabidiolic acid (CBDA) was close to 1:99 (w/w) in secretory cavity contents, however, it was roughly 1:20 (w/w) in the air-dried inflorescence. In addition, Δ9-tetrahydrocannabivarin (Δ9-THCV) and Δ9-tetrahydrocannabivarinic acid (Δ9-THCVA) were only detected in the air-dried inflorescence sample, and the ratio of Δ9-THCV to Δ9-THCVA was about 1:20 (w/w). Besides, cannabidivarinic acid (CBDVA) was only observed in the secretory cavity content.

Experimental Analysis of Tear Fluid and Its Processing for the Diagnosis of Multiple Sclerosis.

A pilot analysis of the tear fluid of patients with multiple sclerosis (MS) collected by glass microcapillary was performed using various experimental methods: liquid chromatography-mass spectrometry, Raman spectroscopy, infrared spectroscopy, and atomic-force microscopy. Infrared spectroscopy found no significant difference between the tear fluid of MS patients and the control spectra; all three significant peaks were located at around the same positions. Raman analysis showed differences between the spectra of the tear fluid of MS patients and the spectra of healthy subjects, which indicated a decrease in tryptophan and phenylalanine content and changes in the relative contributions of the secondary structures of the polypeptide chains of tear proteins. Atomic-force microscopy exhibited a surface fern-shaped dendrite morphology of the tear fluid of patients with MS, with less roughness on both oriented silicon (100) and glass substrates compared to the tear fluid of control subjects. The results of liquid chromatography-mass spectrometry showed downregulation of glycosphingolipid metabolism, sphingolipid metabolism, and lipid metabolism. Proteomic analysis identified upregulated proteins in the tear fluid of patients with MS such as cystatine, phospholipid transfer protein, transcobalamin-1, immunoglobulin lambda variable 1-47, lactoperoxidase, and ferroptosis suppressor protein 1; and downregulated proteins such as haptoglobin, prosaposin, cytoskeletal keratin type I pre-mRNA-processing factor 17, neutrophil gelatinase-associated lipocalin, and phospholipase A2. This study showed that the tear proteome in patients with MS is modified and can reflect inflammation. Tear fluid is not a commonly used biological material in clinico-biochemical laboratories. Experimental proteomics has the potential to become a promising contemporary tool for personalized medicine, and it might be applied in clinical practice by providing a detailed analysis of the tear-fluid proteomic profile of patients with MS.

Isotope dilution mass spectrometry as an independent assessment method for mass measurements of milligram quantities of aqueous solution

Isotope dilution mass spectrometry was used to independently assess the accuracy of mass measurement methods developed to quantitatively dispense milligram quantities of aqueous solution. Solutions of isotopically enriched 158Gd and enriched 155Gd were prepared with the molality (mol g−1) of the 155Gd solution being approximately 400 times more dilute than the 158Gd solution. Aliquots of the 158Gd solution were flame sealed in glass ampoules and the 155Gd solution was quantitatively dispensed as a series of 1-g sample aliquots and larger (45 g–55 g) calibration aliquots. Calibration mixes of the solutions were prepared by mass and the Gd isotopic compositions of the 155Gd, 158Gd, and mixed Gd calibration solutions were measured using a high-resolution multi-collector inductively coupled plasma mass spectrometer. These data were used to calculate an elemental amount ratio for Gd in the solutions. Several 155Gd solution sample units were then spiked with small aliquots (0.25 mg–6 mg) of 158Gd solution for which the masses were determined using glass microcapillary and inkjet dispensing methods. The measured Gd isotopic compositions of these mixed solutions, along with the previously calibrated Gd elemental amount ratio and the known masses of the 155Gd aliquots, were used to calculate masses of dispensed 158Gd solution samples. These isotope dilution-based mass measurements have relative expanded uncertainties <0.1% (k = 2), which will allow solution masses measured by microcapillary and inkjet dispensing methods to be assessed for accuracy.

A simple and reliable microfabrication process for a programmable microvalve array

We describe our reliable methodology for fabricating a complex programmable microvalve array (PMA) and its integration with a glass microcapillary electrophoresis chip. This methodology is applicable to any device that requires multilayered PDMS, multiple alignment processes, selective PDMS bonding, and multilayered integration with downstream sensing systems. Along with the detailed step-by-step process, we discuss essential quality assurance checks that can be performed throughout fabrication to assist in troubleshooting and maximizing chip yield.•Comprehensive instructions for designing and fabricating a programmable microvalve array.•Selective bonding of PDMS and glass by microcontact printing.•Numerous quality control procedures to boost chip yield.

Liquid crystal microcapillary-based sensors for affordable analytical applications.

Stimuli-responsive properties of liquid crystals (LCs), when combined with their optical properties, offer sensitive and rapid sensing applications. Here, we propose and demonstrate a microcapillary-based method to be applied for the online detection of amphiphilic species, which can be further used for tracking biological and chemical species in aqueous media. Specifically, we used compartments (300-1400 μm) of nematic 4-cyano-4'-pentylbiphenyl (5CB) that were positioned into cylindrical glass microcapillaries that promote homeotropic anchoring. The flat surfaces of the cylindrical LC compartments were in contact with an aqueous media. We characterized the equilibrium and nonequilibrium response of LCs upon a change in their anchoring at the aqueous interfaces. Upon anchoring transition, we observed the formation of a positively charged defect at the proximity of the interface that moved to the center of the LC compartment and reached equilibrium, a four-petal configuration. This transition was observed to take an average of 41 ± 19 min., which we related to the motion of the defect due to the imbalance of the elastic forces. During the transition, we observed metastable states which could be removed via thermal treatment. We showed the capillary sensors to be useful considering their ease of additional quantification. We also show that the sensors are reversible that facilitate temporal and cumulative quantification. The findings reported in this study can further be used to develop sensors for specific purposes that require continuous tracking of the chemical and biological species that is critical for the health and safety of the individuals and society.

Refractive Index Sensing in Microfluidic Channels With Integrated Reflectors by Measuring Light Spot Displacement

As several optical properties of a fluid under test depend on its refractive index (RI), there is the need of new sensing approaches for its contactless detection on small sample volumes. To tackle this request, we report a micro-optofluidic sensing platform for measuring the bulk RI of liquid samples inside rectangular section glass microcapillaries with integrated reflectors. In the instrumental setup, a laser beam travels obliquely toward the fluidic channel and it is zigzag guided between the mirrors, crossing the fluid multiple times. When samples with different refractive indices are tested, the light beam is deflected at different angles inside the channel; as a consequence, the output beam position shifts along the microcapillary surface. The position change of the output light spot is then measured by means of a 1-D position-sensitive detector (PSD). Hence, by proper calibration, it is possible to retrieve volumetric RI variations with respect to a reference fluid. Experimental measurements showed a beam displacement per RI unit up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2669~\mu \text{m}$ </tex-math></inline-formula> /RIU, in agreement with the prediction of the theoretical model developed to study light traveling through the microcapillary. The proposed readout technique is contactless and noninvasive, being thus highly suitable for application in several fields, ranging from biology to chemistry to food and beverage industry.

Whispering-gallery-mode sensors for biological and physical sensing

The term whispering gallery mode (WGM) was first introduced to describe the curvilinear propagation of sound waves under a cathedral dome. The physical concept has now been generalized to include light waves that are continuously reflected along the closed concave surface of an optical cavity such as a glass microsphere. The circular path of the internally reflected light results in constructive interference and optical resonance, a morphology-dependent resonance that is suitable for interferometric sensing. WGM resonators are miniature micro-interferometers that use the multiple-cavity passes of light for very sensitive measurements at the microscale and nanoscale, including single-molecule and ion measurements. This Primer introduces various WGM sensors based on glass microspheres, microtoroids, microcapillaries and silicon microrings. We describe the sensing mechanisms, including mode splitting and resonance shift, exceptional-point-enhanced sensing and optomechanical and optoplasmonic signal transductions. Applications and experimental results cover in vivo and single-molecule sensing, gyroscopes and microcavity quantum electrodynamics. We also discuss data analysis methods and the limitations of WGM techniques. Finally, we provide an outlook for molecule, in vivo and quantum sensing.

Vapor Mapping in a Microscopic Space with a Scanning Nanoprobe Interferometer

Evaporation of a liquid inside a microscopic space plays a key role to drive various natural phenomena or chemical/thermal processes in microfluidic systems. So far, fundamental studies in such fields have been indirect due to the lack of techniques geometrically accessible in microscopic spaces. Here, we report on a nanoprobe interferometer that can directly visualize vapor in 3D (dimensions) in a microscopic space. We first optimize the tip geometry of the nanoprobe to enhance its sensitivity just by analyzing the interference patterns during the nanoprobe growth in real time. Based on scanning with the nanoprobe interferometer, vapor concentration from a water meniscus in a glass microcapillary is experimentally mapped, which leads to the measurement of the local evaporation flux from the meniscus. The evaporation flux increases from the capillary center to the wall and decreases with the capillary diameter, mostly due to the Kelvin effect and strong evaporation at the three-phase contact line. Specifically, the flux at the center follows Jv(center) ∝ e–7.7×10–4d, in sharp contrast to the power-law decrease reported. Our nanotechnological methodology would pave the way to explore various questions associated with microscopic, geometrically confined evaporation dynamics which has been experimentally inaccessible so far.

Whispering Gallery‐Mode Microdroplet Tensiometry

Droplets are ideally suited to support high‐Q‐factor whispering gallery modes (WGMs) due to their perfectly smooth surface. WGMs enable extremely precise measurements of the droplet properties such as size and shape. Herein, a simple, fast, and very precise technique to measure interfacial tension (IFT) between two immiscible liquids based on WGMs is demonstrated. A microdroplet is generated at the end of a glass microcapillary, submerged in a continuous liquid phase, and its size changes are monitored with nanometer precision via WGMs, while simultaneously applying finely tunable pressure through the microcapillary. IFT is determined from the size of the droplet and the pressure in the microcapillary at equilibrium. Droplets as small as 8 μm are used, thus requiring extremely small sample volume. The IFT measurements can be carried out also at nonequilibrium state when either the size of the droplet or the chemical composition of the continuous phase changes in time. Simultaneously, the WGMs enable very precise measurement of the refractive index of either the droplet or the continuous phase.

Near Infrared Absorption Spectroscopy in Microfluidic Devices With Selectable Pathlength

In this work we present a smart micro-opto-fluidic platform based on rectangular-section glass micro-capillaries with integrated reflectors. The micro-opto-fluidic setup was exploited for absorption spectroscopy measurements in the near infrared range from 1.0 to 1.7 μm. The external flat sides of the micro-capillaries are coated with thin Aluminum layers to create multipath micro-devices in which light can bounce multiple times. Broadband light provided by a Tungsten lamp is coupled into a multimode optical fiber and shone onto the flat surface of the micro-capillary. After travelling inside the micro-channel filled with the sample, radiation is directed towards an optical spectrum analyzer. The line-shape of the output light spectrum depends on the absorption features of the sample and, in particular, on the concentration of water in alcoholic solutions. Experimental results are in good agreement with the prediction given by the developed theoretical model that describes light transmission through the fluidic micro-channel. Moreover, a responsivity parameter, defined as the output power ratio at two wavelengths, is retrieved: water sensitivity is greatly enhanced by the multipath effect since it is proved to be directly proportional to the light bounces in the micro-channel.

The self-healing investigations on fiber-reinforced polymer composites through a novel compartmented microcapillary approach

This paper presents the experimental self-healing investigations on fiber-reinforced polymer (FRP) composites using a novel in-situ healing approach. During the preparation of polymer composites, the monomer Dicyclopentadiene (DCPD) was embedded as the healing agent. The compartment hollow glass microcapillaries were used to serve the localized distribution of the healing agent. To determine the viability of the proposed microcapillary approach, several flexural tests were conducted to initiate the damage and subsequent realization of self-repair activity. The healing was initiated through the polymerization of DCPD in the presence of Grubb’s catalyst (first and second generation). Once healed, the specimens were tested cyclically to evaluate the recovery of flexural strength. A post-failure healing efficiency as high as 72% has been observed. SEM and XRD investigations have been conducted for the microstructural investigations. These investigations support the potential applications of the proposed concept of embedding the bulk with the microcapillaries.

Spectral Interferometric Detection of NIR Optical Resonances of Rectangular Microcapillaries for Refractive Index Sensing

In this work, we propose a spectral interferometric technique for detecting the wavelength position of the resonances of low-cost optical resonators, consisting in rectangular glass microcapillaries. Moreover, we exploited these microdevices as core elements of a microoptofluidic sensing platform designed for the measurements of the refractive index (RI) of fluid samples, based on spectral phase shift interferometry. A detailed theoretical model was implemented to simulate the spectral shape of the interferometric signal in a wavelength range where cavity resonances of the capillary-based optical resonator occur. For experimental verification, the microdevice was placed at the end of the measurement arm of a Michelson interferometer and illuminated using a light source emitting broadband radiation in the near infrared region around 1.55 μm. The resonances of the empty capillary (i.e., filled with air) were successfully detected as steep phase jumps of the interferometric cosine signal recorded as a function of the wavelength, in good agreement with the theoretical predictions. Finally, further experimental measurements were carried out by filling the capillary channel with water-glucose dilutions with different concentrations to prove the suitability of the phase shift detection method to monitor RI variations with respect to a reference fluid.

X-ray tomography with multiple ultranarrow cone beams.

Hollow glass microcapillaries or x-ray waveguides very efficiently confine x-rays to submicron or nanospots, which can be used for point projection imaging. However, x-ray beams exiting from such devices have ultranarrow cones that are limited by the critical angle for the total external reflection to a few milliradians. Narrow cone beams result in small fields of view, and the application of multiple-reflection optics to cone beam tomography is challenging. In this work, we describe a new nonconventional tomographic geometry realized with multiple confocal ultranarrow cone beams. The geometry enables an increase in the effective radiation cone to over 10° without resolution reduction. The proposed tomographic scans can be performed without truncations of the field of view or limitations of the angular range and do not require sample translations, which are inherent to other multibeam x-ray techniques. Volumetric imaging is possible with a simultaneous iterative reconstruction technique or with a fast approximate noniterative two-step approach. A proof-of-principle experiment was performed in the multipoint projection geometry with polycapillary optics and a multi-pinhole mask inserted upstream of the optics. The geometry is suited for phase-contrast tomography with polychromatic laboratory and synchrotron sources.

Drop-on-demand cell bioprinting via Laser Induced Side Transfer (LIST)

We introduced and validated a drop-on-demand method to print cells. The method uses low energy nanosecond laser (wavelength: 532 nm) pulses to generate a transient microbubble at the distal end of a glass microcapillary supplied with bio-ink. Microbubble expansion results in the ejection of a cell-containing micro-jet perpendicular to the irradiation axis, a method we coined Laser Induced Side Transfer (LIST). We show that the size of the deposited bio-ink droplets can be adjusted between 165 and 325 µm by varying the laser energy. We studied the corresponding jet ejection dynamics and determined optimal conditions for satellite droplet-free bioprinting. We demonstrated droplet bio-printing up to a 30 Hz repetition rate, corresponding to the maximum repetition rate of the used laser. Jet ejection dynamics indicate that LIST can potentially reach 2.5 kHz. Finally, we show that LIST-printed human umbilical vein endothelial cells (HUVECs) present negligible loss of viability and maintain their abilities to migrate, proliferate and form intercellular junctions. Sample preparation is uncomplicated in LIST, while with further development bio-ink multiplexing can be attained. LIST could be widely adapted for applications requiring multiscale bioprinting capabilities, such as the development of 3D drug screening models and artificial tissues.

Small But Powerful Optically: Glass Microcapillaries for Studying Complex Fluids or Biological Systems with Submicrolitre Samples under Harsh Conditions

Small But Powerful Optically: Glass Microcapillaries for Studying Complex Fluids or Biological Systems with Submicrolitre Samples under Harsh Conditions

Spectral Phase Shift Interferometry for Refractive Index Monitoring in Micro-Capillaries.

In this work, we demonstrate spectral phase-shift interferometry operating in the near-infrared wavelength range for refractive index (RI) monitoring of fluidic samples in micro-capillaries. A detailed theoretical model was developed to calculate the phase-sensitive spectral reflectivity when low-cost rectangular glass micro-capillaries, filled with samples with different refractive indices, are placed at the end of the measurment arm of a Michelson interferometer. From the phase-sensitive spectral reflectivity, we recovered the cosine-shaped interferometric signal as a function of the wavelength, as well as its dependence on the sample RI. Using the readout radiation provided by a 40-nm wideband light source with a flat emission spectrum centered at 1.55 µm and a 2 × 1 fiberoptic coupler on the common input-output optical path, experimental results were found to be in good agreement with the expected theoretical behavior. The shift of the micro-capillary optical resonances, induced by RI variations in the filling fluids (comparing saline solution with respect to distilled water, and isopropanol with respect to ethanol) were clearly detected by monitoring the positions of steep phase jumps in the cosine-shaped interferometric signal recorded as a function of the wavelength. By adding a few optical components to the instrumental configuration previously demonstrated for the spectral amplitude detection of resonances, we achieved phase-sensitive detection of the wavelength positions of the resonances as a function of the filling fluid RI. The main advantage consists of recovering RI variations by detecting the wavelength shift of “sharp peaks”, with any amplitude above a threshold in the interferometric signal derivative, instead of “wide minima” in the reflected power spectra, which are more easily affected by uncertainties due to amplitude fluctuations.

Mechano-Optical Analysis of Single Cells with Transparent Microcapillary Resonators.

The study of biophysical properties of single cells is becoming increasingly relevant in cell biology and pathology. The measurement and tracking of magnitudes such as cell stiffness, morphology, and mass or refractive index have brought otherwise inaccessible knowledge about cell physiology, as well as innovative methods for high-throughput label-free cell classification. In this work, we present hollow resonator devices based on suspended glass microcapillaries for the simultaneous measurement of single-cell buoyant mass and reflectivity with a throughput of 300 cells/minute. In the experimental methodology presented here, both magnitudes are extracted from the devices' response to a single probe, a focused laser beam that enables simultaneous readout of changes in resonance frequency and reflected optical power of the devices as cells flow within them. Through its application to MCF-7 human breast adenocarcinoma cells and MCF-10A nontumorigenic cells, we demonstrate that this mechano-optical technique can successfully discriminate pathological from healthy cells of the same tissue type.

One-step deposition and in-situ reduction of graphene oxide in photonic crystal fiber for all-fiber laser mode locking

Films of graphene oxide (GO) were produced on the inner walls of the glass microcapillaries of photonic crystal fibers via insertion of a GO water suspension followed by quick drying with a hot finger (no previous surface functionalization required). Individual capillaries from an array could also be selectively GO coated. Raman hyperspectral images revealed the films to be continuous along tens of centimeters. Furthermore, the films were thermally reduced and, through an annealing process, the concentration of defects in the resulting reduced graphene oxide (rGO) could be decreased. In particular, the two larger microcapillaries of a polarization maintaining photonic crystal fibers were covered with an rGO film, leading to the demonstration of fibers with polarization dependent loss, which were used as mode lockers for pulsed fiber lasers. Pulses as short as 350 fs, with a spectral bandwidth of 8.1 nm, were generated, being shorter than those previously obtained with GO- or rGO-coated non-polarization maintaining photonic crystal fibers.

An instance of intergeneric copulation in the family Rhopalidae (Heteroptera): structure, functioning and congruence of the genitalia in two different species from the standpoint of the lock-and-key hypothesis

n event of mating between specimens of Corizus hyoscyami and Rhopalus parumpunctatus, registered in the Novgorod Province of Russia is considered. The structure of the aedeagi in their completely inflated state and the female genitalia, as well as the functioning of the genitalia, are described and illustrated. The process of unfolding and swelling of the aedeagi is traced using the method of hydraulic inflation of the membranous parts with glass microcapillaries. The congruence of the genitalia is discussed for each species, and also for the interspecific crosses in both combinations of sexes and species. Structures of insect terminalia are divided into three groups according to their functions: 1) auxiliary structures; 2) structures providing the mutual fixation of the genitalia; and 3) structures directly performing the function of transferring seminal fluid. It is shown that in the considered variants of interspecific crosses, the parts of the genitalia belonging to the second group have almost the same structure and functioning, and most likely cannot perform the function of structural isolation. The structures of the third group have taxon-specific morphological and functioning traits and a high degree of congruence within each species. Schemes of the functioning of the genitalia in interspecific crosses, speculatively showing the impossibility of normal insemination, are proposed.

Real-time optofluidic surface-enhanced Raman spectroscopy based on a graphene oxide/gold nanorod nanocomposite.

We demonstrate a glass microcapillary fiber as an optofluidic platform for surface enhanced Raman spectroscopy (SERS), the inner walls of which are coated with a graphene oxide (GO)/gold nanorod (AuNR) nanocomposite. A simple thermal method is used for the coating, allowing for the continuous deposition of the nanocomposite without surface functionalization. We show that the AuNRs can be directly and nondestructively identified on the GO inside the capillaries via identification of the Au-Br SERS peak, as Br- ions from the AuNR synthesis remain on their surface. The coated microcapillary platform is, then, used as a stable SERS substrate for the detection of Rhodamine 6G (R6G) and Rhodamine 640 (RH640) at concentrations down to 10-7 and 10-9 M, respectively. As the required sample volumes are as low as a few hundred nanoliters, down to ~75 femtograms of analyte can be detected. The fiber also allows for the detection of the molecules at acquisition times as low as 0.05 s, indicating the platform's suitability for real-time sensing.