Hydrophilic Tip Research Articles

Stable Air Retention under Water on Artificial Salvinia Surfaces Enabled by the Air Spring Effect: The Importance of Geometrical and Surface‐Energy Barriers, and of the Air Spring Height

AbstractSuperhydrophobic surfaces that can remain dry under water have a high potential as nontoxic antifouling coatings or for drag‐reducing ship coatings. The Salvinia effect leads to impressive stable air layers on underwater submerged floating plants Salvinia, decisively determined by the hydrophilic tips of the otherwise hydrophobic Salvinia hairs (Salvinia paradox). The water adheres to these hydrophilic tips, stabilizing the water–air interface. An even more important contribution to the stability of the air layer is provided by the air spring, which is formed by the air volume bound by the hydrophilic leaf edge and the leaf base. Using an artificial Salvinia model with hydrophobic pillars (syn‐trichomes), how the stability against pressure changes in water depends on the height of the artificial hair is systematically shown: a reduction of the air spring height from 3 mm to 300 µm increases the stability against negative pressure by 500% from 72 to 380 mbar. Thicker air layers react much more strongly when subjected to overpressure (1000 mbar). It is also shown that the presence of a boundary is essential for the function of the air spring: removing the limiting hydrophilic edge around the hydrophobic air spring reduces the stability against negative pressure by 300%.

Atomic wetting of oil droplets into hexagons and stripes

HypothesisPrevious studies showed that liquid droplets can be spherical caps or polygonal shapes on patterned surfaces. We hypothesize that these phenomena can be narrowed down to nanoscale and affecting liquid molecular wetting. We anticipate observing preferential wetting on the underlying substrate with atomic crystalline lattice. ExperimentsThis study explores the wetting behavior of oil nanodroplets deposited on highly ordered pyrolytic graphite (HOPG) with atomic force microscope (AFM). Oil droplets were scanned with hydrophobic and hydrophilic AFM tips in water in peak force mode AFM, carefully controlling the scanning force. Simple modeling was carried out using Surface Evolver to simulate how oil droplets wet on HOPG with molecular lattice. FindingsThe results showed two distinct wetting behaviors: the hexagonal nanodroplets and stripe nanometric films. In both cases, the droplets appear to wet preferentially along preferred orientations which reflect the atomic periodicity of the underlying substrate. This preferential wetting occurs because the atomic roughness is significant at the length scale of the nanodroplets, while the eventual outcome of the wetting (i.e. whether the droplet settles to a finite contact angle, or wets completely into a nanometric film) is dependent on the spreading parameter of the droplet-substrate system, independent of scanning direction.

Changes in cell surface properties of Pseudomonas fluorescens by adaptation to NaCl induced hypertonic stress.

Determination of the effect of water stress on the surface properties of bacteria is crucial to study bacterial induced soil water repellency. Changes in the environmental conditions may affect several properties of bacteria such as the cell hydrophobicity and morphology. Here, we study the influence of adaptation to hypertonic stress on cell wettability, shape, adhesion, and surface chemical composition of Pseudomonas fluorescens. From this we aim to discover possible relations between the changes in wettability of bacterial films studied by contact angle and single cells studied by atomic and chemical force microscopy (AFM, CFM), which is still lacking. We show that by stress the adhesion forces of the cell surfaces towards hydrophobic functionalized probes increase while they decrease towards hydrophilic functionalized tips. This is consistent with the contact angle results. Further, cell size shrunk and protein content increased upon stress. The results suggest two possible mechanisms: Cell shrinkage is accompanied by the release of outer membrane vesicles by which the protein to lipid ratio increases. The higher protein content increases the rigidity and the number of hydrophobic nano-domains per surface area.

A Novel Suction-Irrigation Cannula-Guided Hydrophilic Tip Guidewire Technique of Intraoperative Ureteral Stent Placement During Robot-Assisted Radical Prostatectomy

Background: Patients with large median lobe, history of pelvic radiotherapy, or transurethral resection of the prostate are on the verge of ureteral orifice (UO) injury during robot-assisted radical prostatectomy (RARP). Not all aforementioned patients require ureteral stent placement. Intraoperative findings justify whether to proceed with ureteral stent placement or not. Previously described techniques of intraoperative stent placement involve use of transurethral cystoscopy or suprapubic skin incision, which makes procedure further difficult especially with robotic arms in place.1 Herein, we describe a simple and efficacious method Suction-Irrigation cannula-Guided Hydrophilic Tip guidewire (SIGHT) technique for intraoperative ureteral stent placement. Technique: The case shown here is a 64-year-old gentleman with Gleason 8 prostate cancer and opted for RARP. After division of bladder neck, the interior of the bladder was routinely inspected and the UOs were found too close to the bladder margins. The decision was made to proceed with bilateral ureteral stents placement. To facilitate stent placement, bladder margin is held up using 4th arm of the robot. The bedside assistant inserted laparoscopic suction irrigation cannula from 5 mm assistant trocar. Cannula tip was held a couple of centimeters away from respective UO. A 0.038 Inch diameter, 150 cm long hydrophilic straight tip guidewire is fed into the abdomen through shaft of the cannula. The surgeon on console (A.T.) places the wire into UO and feeds it proximally until the resistance is met. The bedside assistant (R.B.) then feeds the stent over the wire into the abdomen, and the surgeon threads the stent over the wire. The assistance held back-tension on the wire. A pusher is then guided over the wire in similar manner and stent is advanced until distal end of the stent is seen. The wire is pulled out by the bedside assistant, and the distal end of the stent is confirmed with use of robot and secure inside the bladder. Surgery proceeded as usual. Stent placement was verified postoperatively by plain kidney, ureter and bladder radiograph. Patient was discharged next day. Catheter removal was done at postoperative day 7. Ureteral stents were removed under local anesthesia in the office at 4 weeks postoperative visit without complication. Conclusions: Our SIGHT technique is safe, effective, and easily adaptable method for intraoperative ureteral stent placement during robotic procedures. It avoids intraoperative cystoscopy or suprapubic skin incision or use of additional guidewires thereby saving time during which patient is under anesthesia during surgery. Patient Consent Statement: Authors have received and archived patient consent for video recording/publication in advance of video recording of procedure. Music Source:www.epidemicsound.com Copyright: Author owns copyright/license for the music used in the video. A.T. has served as a site-PI on pharma/industry-sponsored clinical trials from Kite Pharma, Lumicell Inc., Dendreon, and Oncovir Inc. He has received research funding (grants) to his institution from Department of Defence, National Institute of Health, Axogen, Intuitive Surgical, Arthur M. Blank Family Foundation, and other philanthropy. A.T. has served as an unpaid consultant to Roivant Biosciences and advisor to Promaxo. He owns equity in Promaxo. Rest of the authors do not have conflict of interests. Runtime of video: 3 mins 21 secs

Effects of the Wettability of a Probing Tip on the Hydration Layer Imaged in Atomic Force Microscopy

Utilizing a fully atomistic molecular dynamics simulation, we uncovered the molecular structure of a hydration layer formed on a hydrophobic carbon sample. By varying the wettability of a probe tip, we investigated how the hydration layer manifests as an image (force) measured in atomic force microscopy. With approaching a tip within 1 nm, the intrinsic hydration layer was significantly perturbed. A hydrophobic tip eventually evaporated the hydration layer at a closer distance, giving an attractive force characteristic of a hydrophobic force. With a hydrophilic tip, the hydration layer persisted with some compression, giving an oscillating force with a period close to the molecular diameter of water.

Rose Pistil Stigma: Hierarchical Superhydrophobic Surfaces with Hydrophilic Microtips for Microdroplet Manipulation.

Finger-like radial hierarchical micropillars with folded tips are observed on the surface of the rose pistil stigma (RPS). Impressively, a water droplet on the surface of the RPS presents a spherical shape and it still hangs on the surface even when the RPS is turned over. Superhydrophobicity and high adhesion to water are demonstrated on the RPS, which is beneficial for the RPS to remain clean and fresh. The special wetting behavior of the RPS is highly related to its hierarchical microstructures and surface chemistry. Finger-like hierarchical micropillars with a high aspect ratio are capable of retaining air to support superhydrophobicity while the microgap between the micropillars and on the hydrophilic tips enables the RPS to retain a high adhesion to water. These findings about the unique wetting behaviors of the RPS may provide inspiration for the design and fabrication of functional wetting surfaces for diverse applications such as microdroplet manipulation, three-dimensional cell culture, and microfluidics.

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

Differences in surface chemistry of regenerated lignocellulose fibers determined by chemically sensitive scanning probe microscopy

Tuning the composition of regenerated lignocellulosic fibers in the production process enables targeting of specific material properties. In composite materials, such properties could be manipulated by controlled heterogeneous distribution of chemical components of regenerated fibers. This attribute requires a visualization method to show their inherent chemical characteristics. We compared complementary microscopic techniques to analyze the surface chemistry of four differently tuned regenerated lignocellulosic fibers. Adhesion properties were visualized with chemical force microscopy and showed contrasts towards hydrophilic and hydrophobic atomic force microscopy tips. Fibers containing xylan showed heterogeneous adhesion properties within the fiber structure towards hydrophilic tips. Additionally, peak force infrared microscopy mapped spectroscopic contrasts with nanometer resolution and provided point infrared spectra, which were consistent to classical infrared microscopy data. With this setup, infrared signals with a spatial resolution below 20 nm reveal chemical gradients in specific fiber types.

Air Retention under Water by the Floating Fern Salvinia: The Crucial Role of a Trapped Air Layer as a Pneumatic Spring.

The ability of floating ferns Salvinia to keep a permanent layer of air under water is of great interest, e.g., for drag-reducing ship coatings. The air-retaining hairs are superhydrophobic, but have hydrophilic tips at their ends, pinning the air-water interface. Here, experimental and theoretical approaches are used to examine the contribution of this pinning effect for air-layer stability under pressure changes. By applying the capillary adhesion technique, the adhesion forces of individual hairs to the water surface is determined to be about 20 µN per hair. Using confocal microscopy and fluorescence labeling, it is found that the leaves maintain a stable air layer up to an underpressure of 65 mbar. Combining both results, overall pinning forces are obtained, which account for only about 1% of the total air-retaining force. It is suggested that the restoring force of the entrapped air layer is responsible for the remaining 99%. This model of the entrapped air acting is verified as a pneumatic spring ("air-spring") by an experiment shortcircuiting the air layer, which results in immediate air loss. Thus, the plant enhances its air-layer stability against pressure fluctuations by a factor of 100 by utilizing the entrapped air volume as an elastic spring.

Superhydrophobic needles tipped with 2‐dimensional arrays of plasmonic colloidal nanoparticles for microdroplet SERS analysis

AbstractAqueous microdroplets strongly attach to metallic needles with superhydrophobic sides and flat hydrophilic tips. Such needles can be made surface‐enhanced Raman spectroscopy (SERS)‐active by adsorbing a layer of densely packed and uniform plasmonic nanoparticles onto the hydrophilic tip. The resulting particle‐tipped needles allow dual enhancement of the Raman signals from microdroplets of low concentration analytes by combining analyte enrichment through solvent evaporation and plasmonic SERS enhancement. The combination of small sample volume, preconcentration, and SERS allows extremely low total amounts of analytes to be detected. Here, we show that with crystal violet as the model analyte, the limit of detection can reach 2 pg. The method can be readily used to fabricate superhydrophobic needles tipped with different types of plasmonic colloidal nanoparticles for enhanced Raman analysis, for example, silver cube tipped needles could be used to detect as little as 2.5 ng of trinitrotoluene.

One-step fabrication of Salvinia-inspired superhydrophobic surfaces with High adhesion

Superhydrophobic surfaces with either low or high adhesion have great significance in numerous engineering domains. Salvinia, a common aquatic plant which has hydrophobic micro hair with a hydrophilic tip on the top, is a nature superhydrophobic surface with high adhesion. Here, inspired by salvinia, a superhydrophobic surface with high adhesion is fabricated by simple polymerization of dopamine (DA) onto nanotips of micro/nanostructured superhydrophobic surface. When the rough superhydrophobic surface is immersed in the DA solution, air is trapped in valley between the micro/nanostructures and discontinuous three-phase contact line (TCL) forms immediately. The polydopamine (PDA) adhesion only occurs on very tips of the micro/nanostructures, while the other ravine part of the micro/nanostructures remained hydrophobic, what endows the superhydrophobic surface numerous hydrophilic tiny tips like the hairs of salvinia leaf. The salvinia-like surface showed superhydrophobic but high adhesive property. This work unfolds more applicabilities of superhydrophobic surface and promotes the application of the superhydrophobic surface.

A simple liquid chromatography-high resolution mass spectrometry method for the determination of glyphosate and aminomethylphosphonic acid in human urine using cold-induced phase separation and hydrophilic pipette tip solid-phase extraction

Recently, the phenomenon of acute poisoning events caused by glyphosate (GLY) had frequently occurred all over the world. The present work reported a simple liquid chromatography-high resolution mass spectrometry (LC-HRMS) method for direct determination of GLY and its metabolite aminomethylphosphonic acid (AMPA) in human urine by combining cold-induced phase separation (CIPS) with hydrophilic pipette tip solid-phase extraction (PTSPE). First, a urine sample was mixed with acetonitrile at a 80% concentration to precipitate proteins. After centrifugation, the mixture was performed a CIPS at −20 °C to enrich GLY and AMPA (six-fold) in the lower water phase which was further performed PTSPE procedure. PTSPE as a miniaturized procedure of SPE, combined with a manual accu-jet® Pro Pipette Controller, was used to extract GLY and AMPA, in which a new type of hydrophilic adsorbent (HILIC powder) based on amide-modified silica was selected as the adsorption of GLY and AMPA. The key factors including the type and the amount of adsorbent, the loading extraction solution, the type and volume of eluent, and the number of aspirating/dispensing cycles were investigated in detail. Meanwhile, the selectivity and sensitivity of GLY and AMPA analysis were improved by the use of LC-HRMS based on targeted single ion monitoring (tSIM) mode without tedious derivatization. This method made a full use of the advantages of these techniques by combining efficient enrichment, effective extraction and selective separation in a simple way. Finally, a comprehensive validation of the method was rigorously executed and the results indicated that the validated method afforded desired linearity, precision, accuracy, and sensitivity.

Hybrid guidewires: Analysis and comparison of the mechanical properties and safety profiles.

Hybrid guidewires are commonly used in urology due to the advantage of an atraumatic hydrophilic tip, which facilitates negotiating tight areas, coupled with an unkinkable nitinol core shaft that is easy to work over due to the Teflon coating. Our aim was to compare the physical and mechanical properties of five commercially available hybrid guidewires to assess their characteristics and functionality. In vitro testing was performed on the following straight-tipped 0.035 inch guidewires: Sensor™ (Boston Scientific), Solo™ Plus (Bard), UltraTrack (Olympus), Rio Tracer™ (Rocamed), and Motion™ (Cook). We evaluated characteristics impacting function (tip flexibility, shaft stiffness, lubricity) and safety (perforation force). Measurements included tip flexibility, lubricity, shaft buckling, and force required to perforate a sheet of aluminum foil. The Motion had the highest tip-bending force (p<0.00001). The Rio Tracer had the stiffest shaft (p<0.00001), followed by the Solo Plus and the Motion, which were significantly stiffer than the Sensor and UltraTrack (p<0.00001). The Solo Plus and UltraTrack had the greatest perforation force (p=0.00023), and the Rio Tracer had the lowest perforation force (p=0.016) when compared to the Sensor. There was no significant difference in frictional force between the five guidewires (p=0.1516). The Solo Plus and UltraTrack required the greatest force to perforate, which conveys a higher safety margin. The RioTracer is the stiffest guidewire, which may be beneficial for instrument insertion with the tradeoff of having a lower perforation force. The clinical significance of higher tip-bending forces (unfavourable) and higher shaft-bending forces (favourable) deserve further investigation.

Three-Dimensional Characterization of Layers of Condensed Gas Molecules Forming Universally on Hydrophobic Surfaces.

Understanding the solvation layer of hydrophobic surfaces is essential for elucidating the interaction between hydrophobic surfaces in aqueous solutions. Despite their importance, little is known on these layers due to the lack of lateral resolution in spectroscopic or scattering experiments and probe instability in the static scanning probe methods used in most experiments. Using a high-resolution FM-AFM with stiff cantilevers and hydrophilic tips, we overcome this instability to provide the first detailed 3d maps of the solvation/hydration layer of two archetypal hydrophobic surfaces: graphite (HOPG) and self-assembled fluoro-alkane monolayer (FDTS). In degassed solutions we find different tip-surface interactions for the two surfaces; hydration oscillations superimposed on van der Waals attraction with HOPG and electrostatic repulsion with FDTS. Both are similar to interactions observed with hydrophilic surfaces. In solutions equilibrated with atmospheric air or high-pressure nitrogen, the tip-surface interaction changes dramatically, disclosing the formation of a 2-5 nm thick layer of condensed gas molecules adsorbed to the hydrophobic surfaces. This layer leads to strikingly similar tip-surface interactions for HOPG and FDTS with only weak dependence upon the concentration of dissolved gas molecules, indicating universality in the way hydrophobic surfaces present themselves to nondegassed aqueous solutions. Measurements at low cantilever oscillation amplitudes reveal the inner structure of the layer of condensed gas molecules with an average distance between its constituents, 0.5-0.8 nm, agreeing with recent molecular dynamics calculations. In addition to the uniform condensed layers, we probe sparse nanobubbles found on the surface. Those show distinct interaction with the tip, different from that with the flat layer.

Wettability of AFM tip influences the profile of interfacial nanobubbles

To accurately characterize the shape of interfacial nanobubbles using atomic force microscopy (AFM), we investigated the effect of wettability of the AFM tip while operating in the peak force tapping (PFT) mode. The AFM tips were made hydrophobic and hydrophilic by Teflon AF coating and oxygen plasma treatment, respectively. It was found that the measured base radius of nanobubbles differed between AFM height images and adhesion images, and that this difference depended on the tip wettability. The force curves obtained during the measurements were also different depending on the wettability, especially in the range of the tip/nanobubble interaction and in the magnitude of the maximum attractive force in the retraction period. The difference suggests that hydrophobic tips penetrate the gas/liquid interface of the nanobubbles, with the three phase contact line being pinned on the tip surface; hydrophilic tips on the other hand do not penetrate the interface. We then quantitatively estimated the pinning position and recalculated the true profiles of the nanobubbles by comparing the height images and adhesion images. As the AFM tip was made more hydrophilic, the penetration depth decreased and eventually approached zero. This result suggests that the PFT measurement using a hydrophilic tip is vital for the acquisition of reliable nanobubble profiles.

Salvinia-Effect-Inspired "Sticky" Superhydrophobic Surfaces by Meniscus-Confined Electrodeposition.

Inspired by the Salvinia effect, we report the fabrication and characterization of a novel "sticky" superhydrophobic surface sustaining a Cassie-Baxter wetting state for water droplets with high contact angles but strong solid-liquid retention. Unlike superhydrophobic surfaces mimicking the lotus or petal effect, whose hydrophobicity and droplet retention are typically regulated by hierarchical micro- and nanostructures made of a homogeneous material with the same surface energy, our superhydrophobic surface merely requires singular microstructures covered with a hydrophobic coating but creatively coupled with hydrophilic tips with different surface energy. Hydrophilic tips are selectively formed by meniscus-confined electrodeposition of a metal (e.g., nickel) layer on top of hydrophobic microstructures. During the electrodeposition process, the superhydrophobic surface retains its plastron so that the electrolyte cannot penetrate into the cavity of hydrophobic microstructures, consequently making the electrochemical reaction between solid and electrolyte occur only on the tip. In contrast to typical superhydrophobic surfaces where droplets are highly mobile, the "sticky" superhydrophobic surface allows a water droplet to have strong local pinning and solid-liquid retention on the hydrophilic tips, which is of great significance in many droplet behaviors such as evaporation.

Amphiphilic self-assembly of semiconductor nanocrystals with heterogeneous compositions(a)(a)Contribution to the Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Paule Pileni.

We describe herein that amphiphilic semiconductor nanocrystals (NCs) self-assembled into network structures with heterogeneous compositions. The semiconductor nanorods and tetrapods were subjected to ligand exchange with short-chained water-soluble thiolates, giving an amphiphilic surface pattern with a hydrophilic wall and hydrophobic tips. The amphiphilic NCs self-assembled through hydrophobic effects between tip-surfaces in water. The hydrophobic effect-facilitated self-assembly of NCs was well reproduced by a dissipative particle dynamics simulation. The amphiphilic self-assembly of NCs was demonstrated regardless of NC-shapes and compositions to give semiconductor NC-network structures with heterogeneous compositions. The tandem connection of luminescent core/shell nanorods demonstrated energy transfer between the nanorods in the self-assembly.

How to Improve Cannulation Rates During Endoscopic Retrograde Cholangiopancreatography

How to Improve Cannulation Rates During Endoscopic Retrograde Cholangiopancreatography

Modern flexible ureteroscopy in Cohen cross-trigonal ureteral reimplantations

We describe a feasible flexible ureteroscopy (fURS) technique with the latest instruments to and to discuss their advantages. Three patients underwent a fURS for stone treatment. A 7F angled orifice catheter and a hydrophilic angled tip stiff wire is used to guide the wire in the proper ureteral direction sighting the ureter allowing the use of a 10/12 ureteral access sheath. A single use ureteroscope was used. All of them had successful ureteral access and laser lithotripsy being stone free endoscopically. No complications reported. The modern fURS technique was found feasible and safe in patients with cross-trigonal ureteroneocystostomy.

Nanometer-Sized Water Bridge and Pull-Off Force in AFM at Different Relative Humidities: Reproducibility Measurement and Model Based on Surface Tension Change.

This article deals with the analysis of the relationship between the pull-off force measured by atomic force microscopy and the dimensions of water bridge condensed between a hydrophilic silicon oxide tip and a silicon oxide surface under ambient conditions. Our experiments have shown that the pull-off force increases linearly with the radius of the tip and nonmonotonically with the relative humidity (RH). The latter dependence generally consists of an initial constant part changing to a convex-concave-like increase of the pull-off force and finally followed by a concave-like decrease of this force. The reproducibility tests have demonstrated that the precision limits have to be taken into account for comparing these measurements carried out under atmospheric conditions. The results were fitted by a classical thermodynamic model based on water-bridge envelope calculations using the numerical solution of the Kelvin equation in the form of axisymmetric differential equations and consequent calculation of adhesive forces. To describe the measured data more precisely, a decrease of the water surface tension for low RH was incorporated into the calculation. Such a decrease can be expected as a consequence of the high surface curvature in the nanometer-sized water bridge between the tip and the surface.