Standard Tip Research Articles

Integration of paper and micropipette tip to build a “sample-in, answer-out” point-of-care device

Significant progress has been achieved using paper-based microfluidics to provide low-cost analytical tools for point-of-care testing. To satisfy minimized liquid handling and biohazard contamination risks, we have innovatively integrated microfluidic paper-based analytical devices with a standard micropipette tip to build an economical “sample-in, answer-out” device, namely “strips-in-tip.” The device was assembled by loading multiple chromatography filter paper strips into a micropipette tip. One aspiration action of the pipette can accurately transfer solution samples into the paper strip, and the visual colorimetric results can be read by the naked eye. The multiplexing capability of the strips-in-tip device was demonstrated by assaying glucose, protein, and pH in a urine sample by one aspiration action. Owing to the simplicity of its fabrication and usage, it is anticipated that the strips-in-tip device can be used for biological and chemical assays to avoid contamination and infection.

Biomechanical Evaluation of a Growth-Friendly Rod Construct

BackgroundDistraction-type rods mechanically stabilize the thorax and improve lung growth and function by applying distraction forces at the rib, spine, pelvis, or a combination of locations. However, the amount of stability the rods provide and the amount the thorax needs is unknown. MethodsFive freshly frozen and thawed cadaveric thoracic spine specimens were tested for lateral bending, flexion/extension, and axial rotation in displacement control (1°/sec) to a load limit of ±5 Nm for five cycles after which a growth-friendly unilateral rod was placed in a simulated rib-to-lumbar attachment along the right side. The specimens were tested again in the same modes of bending. From the seven Optotrak Orthopedic Research Pin markers (Northern Digital Inc., Waterloo, Ontario, Canada) inserted into the top potting to denote T1, and the right pedicles at T2, T4, T5, T8, T9, and T11 and the Standard Needle Tip Pressure Transducers (Gaeltech, Isle of Skye, Scotland) inserted into the T4/T5 and T8/T9 discs, motion, stiffness, and pressure data were calculated. Parameters from the third cycle of the intact case and the construct case were compared using two-tailed paired t tests with 0.05 as the level of significance. ResultsWith the construct attached, the T1–T4 segment showed a 30% increase in neutral zone stiffness during extension (p = .001); the T8–T12 segment experienced a 63% reduction in the in-plane range of motion during flexion (p = .04); and the T8/T9 spinal motion unit had a significant decrease of 24% in elastic zone stiffness during left axial rotation (p = .04). ConclusionsIt is clear the device as tested here does not produce large biomechanical changes, but the balance between providing desired changes while preventing complications remains difficult.

Numerical investigation of a HPT with different rotor tip configurations in terms of pressure ratio and efficiency

The choice of the most appropriate rotor tip configuration is important, because it helps to avoid high blade tip losses due to the leakage flow that are responsible for efficiency and pressure ratio drops, mainly in High Pressure Turbine (HPT). This subject has been investigated to improve the axial turbines performance. The HPT used in this work is the turbine designed during the Energy Efficient Engine Program (E3 Program). This HPT was evaluated with different rotor tip geometry configurations: without tip clearance (hypothetical condition), with standard tip clearance geometry (flat-tip), with squealer, with winglet and squealer with winglet. Results were obtained based on the three-dimensional turbulent flow calculations making the use of a commercial CFD RANS equation-based solver with the addition of a two-equation turbulence model, in which the numerical solutions were compared with data available in the open literature for a HPT design-point operation. It was determined that for the HPT studied in this work, the machine efficiency can be improved using the rotor tip geometry equipped with winglet tip configuration. However, the rotor tip geometry equipped with squealer–winglet tip configuration presented a better pressure ratio compromise.

The double guidewire approach for transcoronary pacing in aporcine model.

Transcoronary pacing is used for treatment of unheralded bradycardias in the setting of percutaneous coronary interventions (PCI). In the present study we introduced anew concept - the double guidewire approach - for transcoronary pacing in aporcine model. Transcoronary pacing was applied in 16adult pigs under general anaesthesia in an animal catheterization laboratory. Aspecial guidewire with electrical insulation by PTFE coating except for the distal part of the guidewire was positioned in the periphery of acoronary artery serving as the cathode. As the indifferent anode, an additional standard floppy tip guidewire was advanced into the proximal part of the same coronary vessel. The efficacy of double guidewire transcoronary pacing was assessed by measurement of threshold and impedance data and the magnitude of the epicardial electrogram compared with unipolar transcoronary pacing using astandard cutaneous patch electrode as indifferent anode. Transcoronary pacing was effective in all cases. Pacing thresholds obtained with the double guidewire technique (1.5± 0.9 V) were similar to those obtained by standard unipolar transcoronary pacing with acutaneous patch electrode (1.2± 0.7 V) and unipolar transvenous pacing against the same cutaneous patch electrode (1.5± 1.0 V). Bipolar transvenous pacing yielded the lowest pacing threshold at 0.8± 0.4 V. Transcoronary pacing in the animal model with the novel "double guidewire approach" is asimple and effective pacing technique with comparable pacing thresholds obtained by standard unipolar transcoronary and transvenous pacing.

Alternative blade materials for technical and ecological optimization of a hydraulic pressure machine

The Hydraulic Pressure Machine (HPM) is an energy converter to exploit head differences between 0.5 and 2.5 m in small streams and irrigation canals. Previous investigations show that efficiencies above 60% are possible. Several case studies indicate good continuity for aquatic life (e.g. fish) and bed load for the technology. The technology is described as an economically and ecologically viable option for small scale hydropower generation. Primary goal of this research is to improve the HPM blade design regarding its continuity properties by maintaining good efficiency rates. This is done by modifying the blade tip and testing within a large physical model under laboratory condition. Blade tips from steel (conventional - reference case) and a combination of EPDM rubber and steel as sandwich construction (rubber, steel, rubber - adhesive layered) are tested and compared. Both materials reach similar values for hydraulic efficiency (approx. 58%) and mechanical power output (approx. 220 W). The variation of different gap sizes pointed out the importance of small clearance gaps to reach high efficiencies. For assessing the two blade tip materials regarding continuity for aquatic life, fish dummies were led through the wheel. Analysis of slow motion video of dummies hit by the blade show significant advantages for the EPDM blade tip. The EPDM rubber allows to bend and thus reduces the shock and the probability for cuts on the fish dummy. It was shown that blade tips from EPDM have certain advantages regarding continuity compared to standard blade tips from steel. No compromise regarding energy production had to be made. These results from the HPM can be transferred to breast shot water wheel and may be applied for new and retrofitting projects.

Sharp-Tip Silver Nanowires Mounted on Cantilevers for High-Aspect-Ratio High-Resolution Imaging.

Despite many efforts to fabricate high-aspect-ratio atomic force microscopy (HAR-AFM) probes for high-fidelity, high-resolution topographical imaging of three-dimensional (3D) nanostructured surfaces, current HAR probes still suffer from unsatisfactory performance, low wear-resistivity, and extravagant prices. The primary objective of this work is to demonstrate a novel design of a high-resolution (HR) HAR AFM probe, which is fabricated through a reliable, cost-efficient benchtop process to precisely implant a single ultrasharp metallic nanowire on a standard AFM cantilever probe. The force-displacement curve indicated that the HAR-HR probe is robust against buckling and bending up to 150 nN. The probes were tested on polymer trenches, showing a much better image fidelity when compared with standard silicon tips. The lateral resolution, when scanning a rough metal thin film and single-walled carbon nanotubes (SW-CNTs), was found to be better than 8 nm. Finally, stable imaging quality in tapping mode was demonstrated for at least 15 continuous scans indicating high resistance to wear. These results demonstrate a reliable benchtop fabrication technique toward metallic HAR-HR AFM probes with performance parallel or exceeding that of commercial HAR probes, yet at a fraction of their cost.

AFM tips on demand

Tips for atomic force microscopy can now be added to the list of custom lab ware that commercial three-dimensional printers can create. Using a technique known as two-photon polymerization, researchers led by Hendrik Holscher of Karlsruhe Institute of Technology have printed AFM tips of their own design with a resolution of about 25 nm (Appl. Phys. Lett. 2016, DOI: 10.1063/1.4960386). Scientists first created AFM tips with two-photon polymerization more than 10 years ago, but the Karlsruhe team is the first to couple the technique’s resolution with the design flexibility and on-demand capabilities of 3-D printing. In one demonstration, the team printed long, narrow tips that could better trace the steep peaks and valleys of a rose petal’s surface than some standard tips. Although commercial tip providers offer a range of tip geometries, getting the best tip for a unique specimen can be costly, Holscher explains. The two-photon printing technique is

High-resolution imaging of the nanostructured surface of polyacrylonitrile-based fibers

In our study, we present atomic force microscopy (AFM) investigations of the surface of Polyacrylonitrile-based carbon fibers utilizing two different AFM probes, a standard tip as used in literature up to now and a recently made available super sharp tip. Using the super sharp tip, we identified so far not reported pore-like nanostructures distributed homogeneously over the surface of the fibers. We show that such nanopores are already present on the surface of the corresponding precursor fiber, indicating that these structures are characteristic for the fiber along the production process. To investigate a possible correlation between the surface structures and the mechanical properties of carbon fibers, we further analyzed the surface of various carbon fibers showing different tensile strengths. All investigated fibers show characteristic nanoporous surface structures and a correlation was found between the Nanopore size and shape and the mechanical properties. The effective nanopore area and the aspect ratio of the nanopores decrease with increasing tensile strength of the fibers. In addition, the nanoroughness of the fiber surface is correlated to the nanopore size and also decreases with increasing tensile strength.

Long spin lifetime and large barrier polarisation in single electron transport through a CoFe nanoparticle.

We have investigated single electron spin transport in individual single crystal bcc Co30Fe70 nanoparticles using scanning tunnelling microscopy with a standard tungsten tip. Particles were deposited using a gas-aggregation nanoparticle source and individually addressed as asymmetric double tunnel junctions with both a vacuum and a MgO tunnel barrier. Spectroscopy measurements on the particles show a Coulomb staircase that is correlated with the measured particle size. Field emission tunnelling effects are incorporated into standard single electron theory to model the data. This formalism allows spin-dependent parameters to be determined even though the tip is not spin-polarised. The barrier spin polarisation is very high, in excess of 84%. By variation of the resistance, several orders of magnitude of the system timescale are probed, enabling us to determine the spin relaxation time on the island. It is found to be close to 10 μs, a value much longer than previously reported.

Comparison of a torsional and a standard tip with a monitored forced infusion phacoemulsification system

To compare the relative efficiency and chatter of the 30-degree 0.9mm Kelman tip (standard tip) and Ozil Intrepid Balanced tip (torsional tip) with identical optimum settings. John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. Experimental study. Porcine nuclei were fixed in formalin and cut into 2.0mm cubes. Lens cubes were phacoemulsified with standard and torsional tips at 60% and 100% torsional amplitude with 0%, 25%, 50%, 75%, and 100% longitudinal power with monitored forced infusion. Experiments were performed at a constant vacuum, aspiration rate, and intraocular pressure. Linear regression showed increased efficiency with up to 75% longitudinal power at 60% torsional amplitude for both tips (P=.046 standard; P=.0093 torsional). Longitudinal did not significantly increase efficiency at 100% torsional power for either tip. Torsional tips were on average 29% more efficient than standard tips throughout the range tested (P<.0001), and 100% torsional power was on average 45% more efficient than 60% torsional power (P=.0028). Chatter was minimal except at 100% longitudinal power, which was greater than at 75% longitudinal power (P<.0001). At 100% longitudinal power, torsional tips had more chatter than standard tips (at 60% torsional, P<.0001; at 100% torsional, P=.0022). Increasing up to 75% longitudinal power increased the efficiency at 60% torsional for standard and torsional tips. Torsional tips were more efficient than standard tips. Chatter was generally minimal. Torsional tips showed more chatter than standard tips at 100% longitudinal power. None of the authors has a financial or proprietary interest in any material or method mentioned.

Theoretical study of carbon-based tips for scanning tunnelling microscopy

Motivated by recent experiments, we present here a detailed theoretical analysis of the use of carbon-based conductive tips in scanning tunnelling microscopy. In particular, we employ ab initio methods based on density functional theory to explore a graphitic, an amorphous carbon and two diamond-like tips for imaging with a scanning tunnelling microscope (STM), and we compare them with standard metallic tips made of gold and tungsten. We investigate the performance of these tips in terms of the corrugation of the STM images acquired when scanning a single graphene sheet. Moreover, we analyse the impact of the tip-sample distance and show that it plays a fundamental role in the resolution and symmetry of the STM images. We also explore in depth how the adsorption of single atoms and molecules in the tip apexes modifies the STM images and demonstrate that, in general, it leads to an improved image resolution. The ensemble of our results provides strong evidence that carbon-based tips can significantly improve the resolution of STM images, as compared to more standard metallic tips, which may open a new line of research in scanning tunnelling microscopy.

The performance characteristics of a piezoelectric ultrasonic dental scaler

The objective of this work was to investigate the performance characteristics of a piezoelectric ultrasonic dental scaler using scanning laser vibrometry. The vibration characteristics of three standard piezoelectric tips were assessed with scanning laser vibrometry under various conditions: unconstrained, under a stream of flowing water, in a water tank, as well as subjected to loads to simulate clinical conditions. Subsequently, the tips were used to disrupt an in-vitro biofilm model of dental plaque, developed using a non-pathogenic Gram-negative species of Serratia (NCIMB40259).The laser vibrometry data showed that the oscillation pattern of the ultrasonic tip depends primarily on its shape and design, as well as on the generator power. Thin tips and high power settings induce the highest vibrations. Water irrigation of the tip and loads influence the tip performance by diminishing its vibration, while water volume increases it.Serratia biofilm was disrupted by the cavitation bubbles occurring around the scaler tip. The most effective biofilm removal occurred with the thinner tip.Understanding how the ultrasonic tip oscillates when in use and how it removes dental plaque is essential for gaining more knowledge regarding the cleaning mechanisms of the ultrasonic system. Cavitation may be used to remove plaque and calculus without a mechanical contact between the dental tip and the teeth. Better knowledge would enable dental specialists to understand and improve their techniques during routine cleaning of teeth. It will also lead to improving tip design and to the production of more effective instruments for clinical use.

Polymer optical fiber compound parabolic concentrator tip for enhanced coupling efficiency for fluorescence based glucose sensors.

We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip. We use Zemax modelling to find the optimum CPC tip profile and fiber length of a polymer optical fiber diabetes sensor for continuous monitoring of glucose levels. We experimentally verify the improved performance of the CPC tipped sensor and the predicted production tolerances. Due to physical size requirements when the sensor has to be inserted into the body a non-optimal fiber length of 35 mm is chosen. For this length an average improvement in efficiency of a factor of 1.7 is experimentally demonstrated and critically compared to the predicted ideal factor of 3 in terms of parameters that should be improved through production optimization.

Evaluation of Novel Ball-Tip Holmium Laser Fiber: Impact on Ureteroscope Performance and Fragmentation Efficiency

A novel ball tip (BT) holmium laser fiber has recently been developed, which features a modified rounded tip. The modification is purported to aid in insertion and minimize damage to the ureteroscope working channel. We evaluated this laser fiber with regard to stone comminution, tip degradation, insertional force into the ureteroscope, and impact on ureteroscope deflection. A 242 μm BT fiber and a standard flat tip (SF) fiber were compared. Four kilojoules was delivered to a BegoStone over a constant surface area using settings of 0.2/50, 0.6/6, 0.8/8, and 1 J/10 Hz. Fiber tip degradation was measured at 1 and 4 kJ. Ureteroscope deflection was measured with the Olympus URF-P5, URF-P6, and URF-V. Insertion force into a 270° angled ureteroscope sheath model was measured. A sample size of five fibers was used for each comminution energy setting. Comminution increased with pulse energy without significant difference between fibers. No significant differences in tip degradation were observed. Both fibers reduced deflection (10°-30°) in all ureteroscopes without significant differences between fibers. Four new fibers paired with new sheath models were used to test insertion force. The BT insertion forces were approximately one-third of the SF. One SF fiber caused significant damage to the sheath and could not be advanced completely. The BT fiber has comparable comminution, tip degradation, and ureteroscope deflection performance compared with the SF fiber while exhibiting reduced insertion force within an aggressively deflected working sheath. The new tip design is likely protective of the working channel without loss of performance.

Lithotripsy Performance of Specially Designed Laser Fiber Tips

We evaluated and compared a standard laser lithotripsy fiber to laser fibers claimed to have lithotripsy performance enhancing features. A special AccuMax™ 200 polished tip fiber and an AccuTrac™ ball-shaped tip fiber, each with an approximately 240 μm core, were compared to a standard 272 μm core fiber (Rocamed™). The polished and ball-shaped tip fiberswere used and reused without preparation. The standard fiber was stripped and cleaved according to manufacturer instructions after eachexperiment. An automated laser fragmentation testing system was used toperform multiple 30-second laser lithotripsy experiments. To mimic most typical lithotripsy conditions soft and hard stone materials were used with high frequency, low pulse energy (20 Hz and 0.5 J) or with low frequency, high pulse energy (5 Hz and 2.0J) lithotripter settings. Ablation volumes and laser fiber tip photographs before and after lithotripsy were compared. The standard and ball-shaped tip fibers did not differ in ablation volume (p = 0.72) but they ablated 174% and 188% more stone, respectively, than the polished tip fiber (p <0.0001). The ball-shaped tip showed remarkable fiber tip degradation after short-term use at low frequency, high pulse energy settings. When high pulse energy settings were applied first even for short-term use, the ablation volume achieved by the polished and ball-shaped tip fibers at high frequency, low pulse energy settings decreased more than 20%. The standard laser fiber was as good as and sometimes better than the specially designed fibers. Rapid degradation of the specially designed laser fiber tips strongly limits their general usefulness but ball-shaped tip fibers may be useful in specific situations.

Magnetic scanning gate microscopy of a domain wall nanosensor using microparticle probe

We apply the magnetic scanning gate microscopy (SGM) technique to study the interaction between a magnetic bead (MB) and a domain wall (DW) trapped in an L-shaped magnetic nanostructure. Magnetic SGM is performed using a custom-made probe, comprising a hard magnetic NdFeB bead of diameter 1.6µm attached to a standard silicon tip. The MB–DW interaction is detected by measuring changes in the electrical resistance of the device as a function of the tip position. By scanning at different heights, we create a 3D map of the MB–DW interaction and extract the sensing volume for different widths of the nanostructure's arms. It is shown that for 50nm wide devices the sensing volume is a cone of 880nm in diameter by 1.4µm in height, and reduces down to 800nm in height for 100nm devices with almost no change in its diameter.

PWE-008 Multicentre randomised trial comparing eus guided fine needle aspiration cytology (fnac) with fine needle aspiration biopsy (fna b) in sampling solid pancreatic mass lesions: preliminary results from the procore trial

Introduction EUS-guided FNA is the standard of care for tissue sampling of pancreatic lesions. The new Echo Tip ProCore biopsy needle (Cook Medical) was developed to obtain core tissue specimens for histological analysis improving the diagnostic yield and potentially obviating the need for onsite cytopathologist. Our aim was to compare the standard Echo tip ultra FNAC needle with the new Echo Tip Ultra ProCore FNAB needle in the sampling of solid pancreatic lesions. Method Randomised multicenter trial (REC Ref 12/EM/0189). All patients referred for EUS-guided tissue sampling of a solid pancreatic mass were invited to participate. Linear EUS (Aloka-Olympus/Hitachi-Pentax) was performed and patients were randomised to either FNAC or FNAB. Due to the nature of the study the endoscopist could not be blinded. A 22G needle was used when sampling from the stomach and a 25G from the duodenum. A maximum of 5 passes were allowed. Sampling time from first insertion of the needle into the lesion to the time the last tissue sample is transferred into the histology pot, number of passes and adequacy for diagnosis were recorded and included for analysis. Immediate and delayed complications were also recorded. Results 266 patients were recruited (median age 67 years, 52% men); 142 randomised to the FNAC group and 124 to the FNAB group. Two patients were excluded after randomization; no mass lesion was seen in 1 patient randomised to FNAC and the needle failed in 1 patient in the FNAB group and FNAC was performed. 264 patients were analysed, 141 in the FNAC group (22G=83 and 25G=58. Median max diameter of the lesion 34 mm, range 10–87 mm) and 123 in the FNAB group (22G=53 and 25G=71. Median max diameter 33 mm, range 8–85 mm). There was no statistical significant difference between groups in number of passes (median 4, range 1–5 in the FNAC group vs. median 3, range 1–5 in the FNAB group, p = 0.12), sampling time (median 13 min, range 1–32 min vs. median 13 min, range 2–42 min, p = 0.63) and adequacy of the specimen for diagnosis (90.8% vs. 87%, p = 0.33). Three technical failures were observed in the FNAB group and none in the FNAC cohort (1.6% vs. 0%, p = 0.99). No complications reported in either group. Conclusion FNAC and FNAB needles were comparable in terms of sampling time, number of passes, sample adequacy for diagnosis and safety. Technical failure was higher in the FNAB arm but not statistically significant. Disclosure of interest None Declared.

Forming reproducible non-lithographic nanocontacts to assess the effect of contact compressive strain in nanomaterials

The application of electrical nanoprobes to measure and characterize nanomaterials has become widely spread. However, the formation of quality electrical contacts using metallic probes on nanostructures has not been directly assessed. We investigate here the electrical behaviour of non-lithographically formed contacts to ZnO nanowires (NWs) and develop a method to reproducibly form Ohmic contacts for accurate electrical measurement of the nanostructures. The contacting method used in this work relies on an electrical feedback mechanism to determine the point of contact to the individual NWs, ensuring minimal compressive strain at the contact. This developed method is compared with the standard tip deflection contacting technique and shows a significant improvement in reproducibility. The effect of excessive compressive strain at the contact was investigated, with a change from rectifying to ohmic I–V behaviour observed as compressive strain at the contact was increased, leading to irreversible changes to the electrical properties of the NW. This work provides an ideal method for forming reproducible non-lithographic nanocontacts to a multitude of nanomaterials.

A refined tip correction based on decambering

AbstractA new tip correction for use in performance codes based on the blade element momentum (BEM) or the lifting‐line technique is presented. The correction modifies the circulation by taking into account the additional influence of the induction of the vortices in the wake, using the so‐called decambering effect and thin‐airfoil theory. A limitation of the standard Prandtl tip correction is that it represents the surface loading by a line distribution that does not take into account the actual shape of the rotor blade. Thus, the chord distribution does not appear as a parameter in the model, and the loading in the proximity of the tip is generally found to be overestimated. The new tip correction is implemented as an additional correction in order to represent the surface loading by a line distribution. Comparing computations using the new model with standard BEM results and computations using a 3D panel code show that the inclusion of the correction greatly improves the results. The new model also explains some of the discrepancies that earlier on have been observed when using a BEM technique based alone upon standard tip corrections. Copyright © 2015 John Wiley &amp; Sons, Ltd.

The effect of needle gauge, needle type, and needle orientation on the volume of a drop.

The purpose of this study was to determine impact of needle gauge, type, and orientation on average volume of drop dispensed. Five needle gauges (22G, 23G, 25G, 27G, and 30G) were examined. For each gauge, volume of drop delivered was determined for standard sharp beveled tip, blunt tip, and after breaking off of the sharp needle from the hub. Vertical and horizontal orientation of the needle was tested for effect on drop volume for 22-G and 30-G sharp beveled needles. Mean drop volume was affected by needle gauge, needle orientation, and whether the needle had been broken off from its hub. Mean drop volume scaled directly with needle diameter with drop volumes of 25.0μL (±20.2) and 83.9μL (±16.5) being found for 30-gauge and 22-gauge needles, respectively. Intermediate gauges (27, 25, 23G) yielded intermediate drop volumes. Blunt needles tended to produce larger drop volumes compared to sharp beveled needles, but these differences did not reach statistical significance. Breaking off of the needle from the hub produced substantially larger drop volumes with little difference being found between needle gauges. Average volumes of 1 drop from a 22-G vertical, 22-G horizontal, 30-G vertical, and 30-G horizontal sharp beveled needle were 20.2, 9.1, 10.1, and 3.3μL, respectively. These findings have relevance for controlled delivery of topical ophthalmic medications to patients.