The authors acknowledge support from Samsung, the NC State Chancellors Innovation Funds, NSF (CAREER CMMI-0954321 and Triangle MRSEC DMR-1121107), and Air Force Research Labs.

1. Manipulation der Grenzflächenspannung des flüssigen Metalls in Electrolyte <ol><li> Oxidation <ol><li> Gießen einer wässrigen Elektrolyten (sauer oder basisch) in eine Petrischale. Um sicherzustellen, daß das Oxid vollständig entfernt wird, verwenden eine Säure oder Base mit einer Konzentration von mehr als 0,1 M 24 (beispielsweise 1 M NaOH oder 1 M HCl). Verwenden Sie ein Volumen, das die Schale bis zu einer Tiefe von ca. 1-3 mm füllen wird. Vermeiden Sie Kontakt mit der Haut mit diesen Lösungen. </li><li> Mit einer Spritze, um einen Tropfen (optimal zwischen 10-500 ul) einer Gallium-Basis-Legierung im Elektrolyt zu platzieren. Beispiele hierfür sind eutektische Gallium-Indium (eGain) oder Gallium-Indium-Zinn (Galinstan). Wenn reinem Gallium verwendet wird, zu erwärmen, daß der Elektrolyt mindestens 30 ° C, um ein Einfrieren zu verhindern. </li><li> Platzieren eines Kupferdrahtes in das flüssige Metall auf die Arbeitselektrode herzustellen. Einen Kupferleiter mit einem Durchmesser kleiner als der der Tropfen, und mit einem Digital-Multimeter nach den Anweisungen des Herstellers, um ENsure, dass der Draht einen Widerstand von &lt;1 Ω. In Säure oder Base, wird das flüssige Metall der Kupfer benetzen und dadurch ein ausgezeichneter elektrischer Kontakt. </li><li> Platzieren eines leitenden Gegenelektrode (beispielsweise Kupfer, Graphit, Platin, etc.) in die Lösung, jedoch nicht in Kontakt mit dem flüssigen Metall. Wenn die Gegenelektrode einen Widerstand von &lt;1 Ω, sind seine Abmessungen irrelevant. </li><li> Verbinden Sie die Kabel mit einer Spannungsquelle und wenden ein positives Potential an das flüssige Metall. Für kleine Form Verformung gelten positive Spannungen &lt;1 V. Bei größeren Form Deformation (und die Bewegung des flüssigen Metalls in Richtung der Gegenelektrode), gelten&gt; 1 V. Anmerkung: Die Konzentration der Lösung und die Entfernung des Abfalls von der Gegenelektrode die Spannung erforderlich, Veränderungen der Grenzflächenspannung zu induzieren, da die Rate der elektrochemischen Oberflächenoxidation konkurriert mit der Rate von Oxidauflösung durch den Elektrolyten zu diktieren. </li></ol></li&gt; <li> Die Ermäßigung <ol><li> Ausgeben einer Abfall (10-500 ul) des flüssigen Metalls von einer Spritze in eine leere Petrischale. </li><li> Gießen einer neutralen wässerigen Elektrolyten in die Petrischale (beispielsweise 1 M Natriumfluorid (NaF) oder 1 M Natriumchlorid (NaCl)) auf ein Niveau, das Metall eintaucht. Anmerkung: Die Verwendung eines sauren (pH &lt;3) oder basischen Lösung (pH&gt; 10) bewirkt, dass das Oxid, spontan zu lösen. </li><li> Platzieren eines Kupferdrahtes in das flüssige Metall als eine Arbeitselektrode und eine stromführende Leitung (beispielsweise Kupfer) in den Elektrolyten, die als Gegenelektrode fungieren zu handeln. </li><li> Verbinden Sie die Kabel mit einer Spannungsquelle und wenden Sie ein negatives Potential an das flüssige Metall. Gelten etwa -1 V, um die Oberflächenoxide zu entfernen, und daß das Metall aus dem Substrat entnetzen. Das Metall sollte auf der Seite, die der Gegenelektrode entnetzen. </li><li> Gelten negativeren Potentialen (&lt;-1 V), um die Oxidschicht vollständig zu entfernen. Vermeiden Sie die Anwendung exceslich große negative Spannungen an Wasserstoffblasen auf das flüssige Metall erscheinen aufgrund der Reduktion des Elektrolyten zu verhindern. </li></ol></li></ol> 2. Oberflächenspannungsmessung über Trauben Droplet <ol><li> Mit Hilfe eines Laser-Cutter oder Fräswerkzeug, schneiden einen direkten Weg von der Mitte bis zum Rand ein Stück Polymethylmethacrylat (PMMA) (~ 1 mm dick) Sie den Pfad zu schneiden nicht den ganzen Weg durch die Dicke der PMMA. nur etwa zur Hälfte geschnitten. Dieses Stück wird als Substrat für das Flüssigmetall zu dienen. Andere flach und elektrisch isolierende Materialien, wie Glas, Keramik oder Polymere können auch als Substrat dienen. </li><li> Mit dem gleichen Werkzeug, schneiden Sie ein 1 mm 2 Loch durch die Mitte des PMMA. </li><li> Verwenden Sie den Pfad als Leitfaden, führen Sie einen isolierten Kupferdraht nur mit der Spitze in die Mitte des PMMA ausgesetzt. Positionieren des Drahtes, so daß er über die PMMA-Oberfläche vorsteht. Verschließen Sie den Draht an Ort und Stelle mit einem dichten Klebstoff. Schneidender Draht gerade über die Oberfläche des PMMA, aber lassen Sie es nicht zu weit zu verlängern (über ~ 100 &amp; mgr; m), oder es wird die Form der Tropfen stören. </li><li> Kleben Sie die PMMA-Stück nach unten in einem transparenten Behälter, durch die ein klares Bild erhalten werden kann. Füllen Sie den Behälter mit 1 M NaOH, und legen Sie eine 25-50 ul Tropfen flüssigen Metalls auf dem hervorstehenden Kupferdraht. Dieser Draht wird als Arbeitselektrode dienen und das Tröpfchen benetzen. </li><li> Platzieren eines Platinnetzes Gegenelektrode und einer gesättigten Silber / Silberchlorid (Ag / AgCl) Referenzelektrode in der Lösung. Verbinden alle Elektroden mit einem Potentiostaten. </li><li> Platzieren des Behälters in einem Kontaktwinkel-Goniometer, so dass das Oberflächenprofil des Tropfens deutlich sichtbar ist. Verwenden des Potentiostaten, um die Spannung in Bezug auf die Referenzelektrode zu steuern, und Verwenden des Goniometers um die Form und damit die Grenzflächenspannung des Tropfens zu messen. Stellen Sie sicher, dass die Winkelmesser für die Messung von ruhenden Tropfens Grenz Tensi istam; es ist auch möglich, benutzerdefinierte achsensymmetrischen Formanalyse Drop Bilder aus einem horizontal angebrachten Kamera 25 aufgenommen zu verwenden. </li></ol> 3. Kapillarinjektion <ol><li> Füllen einer Glaskapillare mit einer Lösung von 1 M NaOH. Kapillardurchmesser sollte ~ 1 mm. </li><li> Platzieren eines Endes der Kapillare bündig mit einem Tropfen des flüssigen Metalls. Ausrichten der Kapillaren, so daß sie parallel zur Oberfläche des Tisches (dh senkrecht zur Schwerkraft) ist. Keine Luftspalten zwischen dem flüssigen Metall Abfall und Elektrolyt-gefüllten Kapillare. Mit einem Wischen, Tupfen Sie überschüssiges Elektrolyt, der während der Montage ausgetreten sein könnten. </li><li> Platzieren eines Kupferdrahtes (Arbeitselektrode) in dem flüssigen Metall und einer leitenden Gegenelektrode (zB Kupferdraht) in das offene Ende der Kapillare, so dass er in Kontakt mit der Lösung. </li><li> Verbinden Sie die Kabel mit einer Spannungsquelle und wenden ein positives Potential an das flüssige Metall. Das flüssige Metall sollte Füllen des c beginnenapillary (vermeiden Sie große Potenziale, die überschüssige Blasenbildung auf der Gegenelektrode verursacht). </li></ol> 4. Kapillar Widerrufsrecht <ol><li> Nutzen softlithographischer 26 und Replika Formtechniken zur mikrofluidischen Kanälen aus Polydimethylsiloxan (PDMS) besteht herzustellen. Herzustellen Kanäle, die etwa 100 bis 1.000 &amp; mgr; m breit sind, 100 um groß, und 25 bis 65 mm lang. Hinweis: Kanalabmessungen 1000 um breit, 100 &amp; mgr; m groß und 65 mm langen Kanal produziert konsistente Ergebnisse, aber andere können auch funktionieren. Alternativ können Glaskapillaren (beispielsweise 1 mm Durchmesser, Borosilikatglas) anstelle des PDMS Mikrokanälen. </li><li> Injizieren Flüssigmetall entweder manuell oder mit Hilfe einer Spritzenpumpe, um den Kanal vollständig zu füllen (dh 6,5 mm 3 für eine 1000 um breit, 100 &amp; mgr; m groß und 65 mm langen Kanal). </li><li> Mit einem Wattestäbchen, das in 1 M NaOH oder 1 M HCl eingetaucht worden ist, entfernen Sie überschüssigen Mengen an liquid Metall von dem Einlass (und, falls erforderlich, der Auslass) des Kanals, so dass das Metall weiterhin bündig mit der oberen Oberfläche der PDMS. </li><li> Unterzutauchen einem Ende des Kanals in dem Elektrolyten (beispielsweise 1 M NaCl) und legen die Anode (beispielsweise Drähte aus Kupfer, Platin oder Wolfram), daß sie den Elektrolyt aber nicht das Metall berührt. </li><li> Am anderen Ende des Kanals, an einen getrennten Elektrode (zB Cu-Draht) auf die Metalloberfläche, so daß flüssiges Metall selbst als Kathode wirkt. </li><li> Verbinden Sie diese Leitungen (dh Anode und Kathode) mit einer Spannungsquelle oder Potentiostaten, und füllen Sie den Stromkreis. Für einen Drei-Elektroden-System, legen Sie die Referenzelektrode, so dass er kaum taucht in den Tropfen des Elektrolyten. </li><li> Vor der Anwendung eines Reduktionsspannung, montieren Sie eine Videokamera auf einem Stativ oder in einem Mikroskop, um die Experimente zu erfassen. Verwenden Sie Autofokus-Modus, um alles im Blick zu bekommen. Nutzen Sie den manuellen Fokus, um eine bessere Kontrolle zu haben überSchärfentiefe, Weißabgleich und ISO. Nutzen Sie gegebenenfalls höhere F Anschlag (dh 11 oder höher), 1/100 Shutter, automatischer Weißabgleich und Auto ISO. </li><li> Starten Sie die Aufnahme des Experiments. Gelten etwa -1 V, um das Flüssigmetall aus den Mikrokanälen zu entziehen. Schalten Sie die Spannung ab, um das Metall verursachen Bewegung in neutralen Elektrolyten zu stoppen. </li></ol>

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The authors have nothing to disclose.

<html> Dieses Verfahren steuert die Oberflächenspannung von Gallium basierenden flüssigen Metallen mit kleinen Spannungen, um die Abscheidung und Entfernung einer Oberflächenoxidschicht zu fahren. Obwohl das Verfahren funktioniert nur in Elektrolytlösungen, es ist einfach und arbeitet in einer Vielzahl von verschiedenen Bedingungen, aber es gibt Feinheiten erwähnenswert. In Abwesenheit von elektrischem Potential, sowohl saure als auch basische Lösungen Wegätzen des Oxids 27. Die Anwendung eines Oxidatio...

This method provides a simple way to control the surface tension of liquid metals containing gallium. The method uses modest voltages (~1 V) applied directly to the liquid metal (relative to a counter electrode in the presence of electrolyte) to achieve enormous and reversible changes to the surface tension of the metal1. 
Surface tension is a dominant force for liquids at small length scales and is important for a number of capillary phenomena including wetting, spreading, and surface-tension driven flow. Consequently, the ability to control surface tension is a sensible way to manipulate the shape, position, and flow of liquids at sub-mm length scales. The most common way to alter surface tension between two fluids is to use a surfactant, which is a molecule that spans the interface between the fluids. Surfactants lower surface tension, but in a way that is not easy to reverse since it is difficult to remove surfactants from the interface. Surface tension can also be altered using a variety of techniques, including temperature gradients2,3, light4, surface chemistry5-7,and voltage8. But most of these methods result in modest changes to surface tension, particularly for liquid metals, which have notably large surface tensions.
The ability to control the surface tension of liquid metal could enable new opportunities for creating shape reconfigurable structures with metallic properties for electronic, thermal, and optical applications9-14. The most common liquid metal is Hg, which is noted for its toxicity. The methods described here are relevant for liquid metals based on gallium. These metals have low viscosity, large surface tension, low volatility (low vapor pressure), and low toxicity15. Importantly, these metals form surface oxides composed of gallium oxide that are a few nm thick in air16. This oxide layer creates a physical skin that historically has been a nuisance for electrochemical and fluid dynamic applications17. The method here utilizes the oxide in new ways to control surface tension.
The most common way to manipulate liquid metals in electrolyte is to apply a potential to the metal relative to a counter electrode18. Oppositely charged ions from the electrolyte match the charges on the metal, causing the interfacial tension to drop. This phenomenon-termed electrocapillarity-has been known since the 1870s as described by Lippman19and has been utilized for alloys of gallium20. Typically, electrocapillarity achieves modest changes to surface tension, since undesirable electrochemical reactions limit the range of voltages applied to the metal. In contrast, the method described here utilizes the surface oxidation of the metal (or conversely, the reduction of the surface oxide) as a way to achieve enormous changes in surface tension above and beyond changes resulting from electrocapillarity. The leading explanation for this phenomenon is that the oxide is asymmetric; that is, the outer surface of the oxide terminates with hydroxyl groups (making a low interfacial tension interface with the aqueous electrolyte), and the interior surface of the oxide terminates with gallium atoms (making a low interfacial tension interface with the metal). In contrast, the removal of the oxide via electrochemical reduction results in a bare metal-electrolyte interface, which returns the metal back to a state of high surface tension. We characterize the interfacial tension of the metal by analyzing the shape of sessile droplets as a function of voltage while assuming that gravity and surface tension are the dominant forces that define the curvature of its surface. 
The advantage of this technique relative to classic electrocapillarity is that it can reversibly tune the tension of low toxicity liquid metals over enormous ranges (from ~500 mN/m to near zero). This delta change in surface tension may be the largest ever reported in literature for any fluid and it can be accomplished in a tunable and reversible manner. These large changes in surface tension are useful for manipulating the capillary behavior of metals; for example, it can induce the metal to spread on a surface, withdraw the metal from microchannels, fill microchannels with metal, and overcome the Rayleigh instabilities to form liquid metal fibers1,21. 
A drawback of this technique is that it requires electrolyte. It works best in acidic or basic conditions, because these electrolytes remove excess surface oxide that would otherwise contaminate the surface of the metal and mechanically restrict the movement of the metal. The simultaneous removal and deposition of the oxide layer complicates the analysis of the interfacial phenomena and it is our hope the methods described in this paper empowers additional analysis. Another disadvantage is that the electrochemical reactions at the surface of the metal must be matched by complimentary half-reactions at the counter electrode22,23. This can lead to hydrogen bubbles forming at the counter electrode.

<table><tbody><tr><td>Eutectic Gallium Indium</td><td>Indium Corporation</td><td></td><td></td></tr><tr><td>Sodium Hydroxide</td><td>Fisher Scientific</td><td>2318-3</td><td></td></tr><tr><td>Hydrochloric Acid</td><td>Fisher Scientific</td><td>A481-212</td><td></td></tr><tr><td>Sodium Fluoride</td><td>Sigma-Aldrich</td><td>201154</td><td></td></tr><tr><td>Optical Adhesive</td><td>Norland</td><td>NOA81</td><td></td></tr><tr><td>Polydimethylsiloxane (Sylgard-184)</td><td>Dow Corning</td><td></td><td>Silicone Elastomer Kit</td></tr><tr><td>Borosilicate Glass Capillaries</td><td>Friedrich and Dimmoch</td><td>B41972</td><td></td></tr><tr><td>Ag/AgCl Reference Electrode</td><td>Microelectrodes Inc.</td><td>MI-401F</td><td></td></tr><tr><td>Voltage Source</td><td>Keithley</td><td>3390</td><td></td></tr><tr><td>Potentiostat</td><td>Gamry</td><td>Ref 600</td><td></td></tr><tr><td>Laser Cutter</td><td>Universal Laser Systems</td><td>VLS 3.50</td><td></td></tr></tbody></table>

a method to manipulate surface tension of a liquid metal via surface oxidation and reduction

Steuern der Grenzflächenspannung ist eine wirksame Methode zur Manipulation der Form, Position und den Fluss von Fluiden bei Submillimeterbereich Längenskalen, wobei die Grenzflächenspannung ist eine dominierende Kraft. Eine Vielzahl von Verfahren existieren zur Steuerung der Grenzflächenspannung von wässrigen und organischen Flüssigkeiten auf dieser Skala; Jedoch wurden diese Techniken Dienstprogramm für flüssige Metalle aufgrund ihrer großen Grenzflächenspannung begrenzt. Flüssige Metalle weich, elastisch und form rekonfigurierbare Komponenten in elektronischen und elektromagnetischer Geräte bilden. Obwohl es möglich ist, um diese Flüssigkeiten durch mechanische Verfahren (zB Pumpen) zu manipulieren, sind elektrische Verfahren einfacher zu miniaturisieren, zu steuern und zu realisieren. Allerdings haben die meisten elektrischen Techniken ihre eigenen Einschränkungen: Electrowetting-on-dielektrischen groß (kV) Potentiale für bescheidene Betätigung kann Elektrokapillarität relativ kleine Änderungen in der Oberflächenspannung beeinflussen und erfordert kontinuierliche electrowetting an Steckern des flüssigen Metalls in Kapillaren beschränkt. Hier stellen wir ein Verfahren zum Betätigen Gallium und Gallium basierenden flüssigen Metalllegierungen mittels einer elektrochemischen Oberflächenreaktion. Steuerung des elektrochemischen Potentials an der Oberfläche des flüssigen Metalls in Elektrolyten schnell und reversibel ändert die Grenzflächenspannung um mehr als zwei Grßenordnungen (̴500 mN / m, um in der Nähe von Null). Weiterhin erfordert dieses Verfahren nur eine sehr bescheidene Potential (&lt;1 V) relativ zu einer Gegenelektrode angelegt. Die resultierende Änderung in der Spannung ist im Wesentlichen auf die elektrochemische Abscheidung einer Oxidschicht auf der Oberfläche, die als ein oberflächenaktives Mittel wirkt; Entfernung des Oxids steigt die Grenzflächenspannung, und umgekehrt. Diese Technik kann in einer Vielzahl von Elektrolyten angewendet werden und ist unabhängig von dem Substrat, auf dem sie ruht.

Figur 1 A zeigt ein Beispiel eines einfachen Zwei-Elektroden-Verfahren für die Oxidation und Reduktion. In diesem Fall wird ein 70 ul Tropfen des flüssigen Metalls in einer 1 M NaOH-Lösung in Kontakt gebracht einen Kupferdraht eine elektrische Verbindung zu etablieren. Das 1 M NaOH beseitigt die Oberflächenoxidschicht von dem Metall und ermöglicht es dem Metall zu perlen aufgrund ihrer Grenzflächenspannung. Aufbringen einer 2,...

Watch this Scientific Journal Video about A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction at JoVE.com

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Eine Methode, die Oberflächenspannung eines Liquid Metal manipulieren via Oberfläche Oxidation und Reduktion

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

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Chemistry

Liquids, Solids, and Intermolecular Forces

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15.2K Aufrufe.  North Carolina State University. We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Serie: A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique.
Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives.
Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation.

The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

Vorteilhafte Reduzierte Droplet-Oberflächen-Wechselwirkung, um den Transport Bioanalyten in Digitale Mikrofluidik Optimieren

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; ...

Forschung

Ingenieurwesen

Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

Ultraschall-Geschwindigkeitsmessung in einem Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

Selektive Bereichsänderung des Siliziumoberfläche Benetzbarkeit durch gepulste UV-Laser-Bestrahlung in flüssigen Umgebung

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

A protocol to avoid the oxidation of metallic substrates during sample transfer from an inhibited acidic solution to an X-ray photoelectron spectrometer is presented.

Die Bestimmung der chemischen Zusammensetzung von Corrosion Inhibitor / Metal-Schnittstellen mit XPS: Minimierung Beitrag Tauch Oxidation

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, ...

Chemie

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

Aerosol-assisted Chemical Vapor Deposition von Metall-Oxid-Strukturen: Zinkoxid-Stangen

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

Vorbereitung und Hochtemperatur-Anti-Adhäsion Verhalten einer rutschigen Oberfläche Edelstahl

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental sciences and industrial applications owing to their periodic arrangement of nanopores with relatively high aspect ratio. However, the techniques reported so far, which could be only valid for mono-surface anodization, show critical disadvantages, i.e., time-consuming as well as complicated procedures, requiring toxic chemicals, and wasting valuable natural resources. In this paper, we demonstrate a facile, efficient, and environmentally clean method to fabricate nanoporous AAOs in sulfuric and oxalic acid electrolytes, which can overcome the limitations that result from conventional AAO fabricating methods. First, plural AAOs are produced at one time through simultaneous multi-surfaces anodization (SMSA), indicating mass-producibility of the AAOs with comparable qualities. Second, those AAOs can be separated from the aluminum (Al) substrate by applying stair-like reverse biases (SRBs) in the same electrolyte used for the SMSAs, implying simplicity and green technological characteristics. Finally, a unit sequence consisting of the SMSAs sequentially combined with SRBs-based detachment can be applied repeatedly to the same Al substrate, which reinforces the advantages of this strategy and also guarantees the efficient usage of natural resources.

A protocol for fabricating nanoporous anodic aluminum oxides via simultaneous multi-surfaces anodization followed by stair-like reverse biases detachments is presented. It can be applied repeatedly to the same aluminum substrate, exhibiting a facile, high-yield, and environmentally clean strategy.

Gleichzeitige Multi-Oberfläche Anodizations und Treppe-wie umgekehrte Vorurteile Ablösung der anodische Aluminium Oxide in Schwefelsäure und Oxalsäure-Elektrolyten

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental ...

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in industry. The wettability of the produced surface was analyzed by bouncing drop experiments and the topography was analyzed by confocal microscopy. In addition, we show various methodologies to measure its durability and anti-icing properties. Superhydrophobic surfaces hold a special texture that must be preserved to keep their water-repellency. To fabricate durable surfaces, we followed two strategies to incorporate a resistant texture. The first strategy is a direct incorporation of roughness to the metal substrate by acid etching. After this surface texturization, the surface energy was decreased by silanization or fluoropolymer deposition. The second strategy is the growth of a ceria layer (after surface texturization) that should enhance the surface hardness and corrosion resistance. The surface energy was decreased with a stearic acid film.
The durability of the superhydrophobic surfaces was examined by a particle impact test, mechanical wear by lateral abrasion, and UV-ozone resistance. The anti-icing properties were explored by studying the ability to repeal subcooled water, freezing delay, and ice adhesion.

We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

Herstellung von Superhydrophob Metalloberflächen für Anti-Icing-Anwendungen

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in ...

Metal-Assisted Electrochemical Nanoimprinting of Porous and Solid Silicon Wafers

Metal-assisted electrochemical imprinting (Mac-Imprint) is a combination of metal-assisted chemical etching (MACE) and nanoimprint lithography that is capable of direct patterning 3D micro- and nanoscale features in monocrystalline group IV (e.g., Si) and III-V (e.g., GaAs) semiconductors without the need of sacrificial templates and lithographical steps. During this process, a reusable stamp coated with a noble metal catalyst is brought in contact with a Si wafer in the presence of a hydrofluoric acid (HF) and hydrogen peroxide (H2O2) mixture, which leads to the selective etching of Si at the metal-semiconductor contact interface. In this protocol, we discuss the stamp and substrate preparation methods applied in two Mac-Imprint configurations: (1) Porous Si Mac-Imprint with a solid catalyst; and (2) Solid Si Mac-Imprint with a porous catalyst. This process is high throughput and is capable of centimeter-scale parallel patterning with sub-20 nm resolution. It also provides low defect density and large area patterning in a single operation and bypasses the need for dry etching such as deep reactive ion etching (DRIE).

A protocol for metal-assisted chemical imprinting of 3D microscale features with sub-20 nm shape accuracy into solid and porous silicon wafers is presented.

Metallgestützte elektrochemische Nanoimprintierung von porösen und festen Siliziumwafern

Metal-assisted electrochemical imprinting (Mac-Imprint) is a combination of metal-assisted chemical etching (MACE) and nanoimprint lithography that is ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.