Low-volume liquid delivery and nanolithography using a nanopipette combined with a quartz tuning fork-atomic force microscope

Direct 3D-printed CdSe quantum dots via scanning micropipette

The micropipette, pencil-shaped with an aperture diameter of a few micrometers, is a potentially promising tool for the three-dimensional (3D) printing of individual microstructures based on its capability to deliver low volumes of nanomaterial solution on a desired spot resulting in micro/nanoscale patterning. Here, we demonstrate a direct 3D printing technique in which a micropipette with a cadmium selenide (CdSe) quantum dot (QD) solution is guided by an atomic force microscope with no electric field and no piezo-pumping schemes. We define the printed CdSe QD wires, which are a composite material with a QD-liquid coexistence phase, by using photoluminescence and Raman spectroscopy to analyze their intrinsic properties and additionally demonstrate a means of directional falling.

Sorting Gold and Sand (Silica) Using Atomic Force Microscope-Based Dielectrophoresis

Additive manufacturing-also known as 3D printing-has attracted much attention in recent years as a powerful method for the simple and versatile fabrication of complicated three-dimensional structures. However, the current technology still exhibits a limitation in realizing the selective deposition and sorting of various materials contained in the same reservoir, which can contribute significantly to additive printing or manufacturing by enabling simultaneous sorting and deposition of different substances through a single nozzle. Here, we propose a dielectrophoresis (DEP)-based material-selective deposition and sorting technique using a pipette-based quartz tuning fork (QTF)-atomic force microscope (AFM) platform DEPQA and demonstrate multi-material sorting through a single nozzle in ambient conditions. We used Au and silica nanoparticles for sorting and obtained 95% accuracy for spatial separation, which confirmed the surface-enhanced Raman spectroscopy (SERS). To validate the scheme, we also performed a simulation for the system and found qualitative agreement with the experimental results. The method that combines DEP, pipette-based AFM, and SERS may widely expand the unique capabilities of 3D printing and nano-micro patterning for multi-material patterning, materials sorting, and diverse advanced applications.

Efficacy of buffered hypertonic seawater in different phenotypes of chronic rhinosinusitis with nasal polyps after endoscopic sinus surgery: a randomized double-blind study

PURPOSE

Nasal douching is commonly used as a postoperative management strategy for chronic rhinosinusitis with nasal polyps (CRSwNP). Few studies to date have compared the effectiveness of nasal douching in CRSwNP phenotypes after endoscopic sinus surgery (ESS). We evaluated the efficacy of seawater types in eosinophilic CRSwNP (ECRSwNP) and noneosinophilic CRSwNP (nonECRSwNP) after ESS.

METHODS

Patients with bilateral CRSwNP who had undergone ESS were blindly randomized to receive buffered hypertonic seawater (BHS) (n = 48) or physiological seawater (PS) (n = 45). CRSwNP patients were stratified by phenotypes (ECRSwNP and nonECRSwNP) retrospectively according to whether tissue eosinophils exceeded 10%. Follow-up evaluations were conducted at 2, 8, 16, and 24 weeks after surgery. Evaluations included the 22-item Sino-Nasal Outcome Test (SNOT-22), visual analog scale (VAS), Lund-Kennedy endoscopic score (LKES), saccharine clearance time (SCT), and adverse events.

RESULTS

All of the patients experienced significant improvements in SNOT-22 scores, VAS scores, and LKES over time. BHS resulted in better improvement of LEKS and SCT relative to PS at 8 weeks postoperatively. Mucosal edema formation was significantly reduced with less crusting among HBS recipients at 8 weeks. After stratification, only patients in the nonECRSwNP + BHS subgroup showed a significant improvement in LEKS and SCT at 8 weeks postoperatively. Side effect profiles were not significantly different among the groups.

CONCLUSIONS

BHS has a better inhibitory effect on mucosal edema and crusting during the early postoperative care period of CRSwNP. Among all of the patients, nonECRSwNP patients showed a significant improvement in LEKS and SCT at 8 weeks.

Viscometry of single nanoliter-volume droplets using dynamic force spectroscopy

We present an atomic force microscope-based platform for viscometry of ‘nanoliter' volume fluids.

Simultaneous Scanning Ion Conductance Microscopy and Atomic Force Microscopy with Microchanneled Cantilevers

We combined scanning ion conductance microscopy (SICM) and atomic force microscopy (AFM) into a single tool using AFM cantilevers with an embedded microchannel flowing into the nanosized aperture at the apex of the hollow pyramid. An electrode was positioned in the AFM fluidic circuit connected to a second electrode in the bath. We could thus simultaneously measure the ionic current and the cantilever bending (in optical beam deflection mode). First, we quantitatively compared the SICM and AFM contact points on the approach curves. Second, we estimated where the probe in SICM mode touches the sample during scanning on a calibration grid and applied the finding to image a network of neurites on a Petri dish. Finally, we assessed the feasibility of a double controller using both the ionic current and the deflection as input signals of the piezofeedback. The experimental data were rationalized in the framework of finite elements simulations.

Mechanisms, Capabilities, and Applications of High-Resolution Electrohydrodynamic Jet Printing

This review gives an overview of techniques used for high-resolution jet printing that rely on electrohydrodynamically induced flows. Such methods enable the direct, additive patterning of materials with a resolution that can extend below 100 nm to provide unique opportunities not only in scientific studies but also in a range of applications that includes printed electronics, tissue engineering, and photonic and plasmonic devices. Following a brief historical perspective, this review presents descriptions of the underlying processes involved in the formation of liquid cones and jets to establish critical factors in the printing process. Different printing systems that share similar principles are then described, along with key advances that have been made in the last decade. Capabilities in terms of printable materials and levels of resolution are reviewed, with a strong emphasis on areas of potential application.

Fabrication and Characterization of Au Nanoparticle-aggregated Nanowires by Using Nanomeniscus-induced Colloidal Stacking Method

We fabricate and characterize Au nanoparticle-aggregated nanowires by using the nano meniscus-induced colloidal stacking method. The Au nanoparticle solution ejects with guidance of nanopipette/quartz tuning fork-based atomic force microscope in ambient conditions, and the stacking particles form Au nanoparticle-aggregated nanowire while the nozzle retracts from the surface. Their mechanical properties with relatively low elastic modulus are in situ investigated by using the same apparatus.

Dynamic and static measurement of interfacial capillary forces by a hybrid nanomechanical system

The forces resulting from the presence of interfacial liquids have mechanical importance under ambient conditions. For holistic understanding of the liquid-mediated interactions, we combine the force-gradient sensitivity of an atomic force microscope (AFM) with the force measuring capability of a micro-electromechanical force sensor. Simultaneous measurement of the viscoelasticity of the water nanomeniscus and the absolute capillary force shows excellent agreement in its entire length, which justifies the validity of the widely used AFM results. We apply the hybrid system to measure the stress and strain, whose hysteretic response provides the intrinsic quantities of the liquid nanocluster.

Nanopipette exploring nanoworld

Nanopipettes, with tip orifices on the order of tens to hundreds of nanometers, have been utilized in the fields of analytical chemistry and nanophysiology. Nanopipettes make nanofabrication possible at liquid/solid interfaces. Moreover, they are utilized in time-resolved measurements and for imaging biological materials, e.g., living cells, by using techniques such as scanning ion-conductance microscopy and scanning electrochemical microscopy. We have successfully fabricated ion-selective nanopipettes that can be used to identify targeted ions such as sodium and potassium in- and outside of living cells. In this review, we discuss the extent of utilization of nanopipettes in investigating the nanoworld. In addition, we discuss the potential applications of future nanopipettes.

Nanopipette combined with quartz tuning fork-atomic force microscope for force spectroscopy/microscopy and liquid delivery-based nanofabrication

This paper introduces a nanopipette combined with a quartz tuning fork-atomic force microscope system (nanopipette/QTF-AFM), and describes experimental and theoretical investigations of the nanoscale materials used. The system offers several advantages over conventional cantilever-based AFM and QTF-AFM systems, including simple control of the quality factor based on the contact position of the QTF, easy variation of the effective tip diameter, electrical detection, on-demand delivery and patterning of various solutions, and in situ surface characterization after patterning. This tool enables nanoscale liquid delivery and nanofabrication processes without damaging the apex of the tip in various environments, and also offers force spectroscopy and microscopy capabilities.

Effect of concentration gradient on ionic current rectification in polyethyleneimine modified glass nano-pipettes

Ion current rectification dependent on the concentration gradient of KCl solutions was systematically investigated in polyethyleneimine modified glass nano-pipettes with inner diameter of 105 nm. Peak shape dependence of the rectification factor on outer KCl solution concentration was observed when inner KCl solution with concentration from 1 mM to 500 mM was used. The peak shape dependence was also observed when the concentrations of the inner and outer KCl solutions were identically controlled. The peak shape in the ion current rectification could be explained by the ion conductance changes through the conical nano-pipette, which result from modulation of ion concentration.

Measurement of line tension on droplets in the submicrometer range

Wetting is a universal phenomenon in nature and of interest in fundamental research as well as in engineering sciences. Usually, wetting of solid substrates by liquid drops is described by Young's equation, which relates the contact angle between the liquid and the substrate to the three interfacial tensions. This concept has been widely used and confirmed for macroscopic droplets. On the contrary, it is still matter of debate to what extent this concept is able to explain relations on the micrometer scale and below. The so-called extended Young's equation, which takes account of the specific arrangement of the molecules in the three-phase contact line by implementing a term called "line tension", is frequently used to characterize deviations from the "ideal" Young's case. In this work we tried to look into the dependence of measured contact angles of droplets on their size for a close to ideal system. We measured contact angles of ionic liquid droplets with radii between some tens and some hundreds of nanometers by atomic force microscopy on an ideally flat silicon wafer. We found that the contact angles decreased with decreasing droplet size: smaller droplets showed stronger wetting. This dependence of the contact angle on the droplet radius could not be described with the concept of line tension or the modified Young's equation. We propose simple arguments for a possible alternative concept.