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. מניפולציה של המתח interfacial של מתכת נוזלית באלקטרוליט <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> חִמצוּן <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> יוצקים אלקטרוליט המימי (חומצי או הבסיסי) לתוך צלחת פטרי. כדי להבטיח שהתחמוצת נמחקה לחלוטין, להשתמש חומצה או בסיס בריכוז העולה על 0.1 M 24 (לדוגמא: 1 M NaOH או 1 M HCl). השתמש בנפח שימלא את הצלחת עד לעומק של כ 1-3 מ&quot;מ. הימנע פנייה העור עם פתרונות אלה. </li><li style=";text-align:right;direction:rtl"> השתמש במזרק למקום טיפה (בצורה אופטימלית בין 10-500 μl) של סגסוגת מבוססת גליום באלקטרוליט. דוגמאות כוללות אינדיום גליום eutectic (EGaIn) או פח אינדיום גליום (Galinstan). אם נעשה שימוש בגליום טהור, לחמם את האלקטרוליט ללפחות 30 מעלות צלזיוס כדי למנוע הקפאה. </li><li style=";text-align:right;direction:rtl"> מניחים חוטי נחושת למתכת הנוזלית להקים את האלקטרודה העבודה. השתמש בחוט נחושת בקוטר פחות מזה של הירידה, ולהשתמש מודד דיגיטלי על פי הוראות יצרן לדוארNsure שיש חוט התנגדות של &lt;Ω 1. בחומצה או בסיס, המתכת הנוזלית תהיה להרטיב את הנחושת ובכך ליצור מגע חשמלי מצוין. </li><li style=";text-align:right;direction:rtl"> הנח האלקטרודה נגדית ביצוע (למשל נחושת, גרפיט, פלטינה, וכו &#39;) בפתרון, אך לא במגע עם המתכת הנוזלית. אם האלקטרודה הנגדית יש התנגדות של &lt;1 Ω, ממדיה אינם רלוונטיים. </li><li style=";text-align:right;direction:rtl"> חבר את החוטים למקור מתח ולהחיל פוטנציאל חיובי למתכת הנוזלית. לעיוות צורה קטנה, תחול מתח חיובי &lt;V. 1 לעיוות גדולה יותר צורה (ותנועה של המתכת הנוזלית לכיוון האלקטרודה הנגדית), תחול&gt; V. 1 הערה: הריכוז של הפתרון והמרחק של הירידה מהאלקטרודה הנגדית להכתיב את המתח הדרוש כדי לגרום לשינויים במתח interfacial מאז קצב חמצון משטח אלקטרוכימיים מתחרה בשיעור של פירוק תחמוצת על ידי אלקטרוליט. </li></ol></li&gt; <li style=";text-align:right;direction:rtl"> צִמצוּם <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> לוותר על ירידה (10-500 μl) של המתכת הנוזלית ממזרק לתוך צלחת פטרי ריקה. </li><li style=";text-align:right;direction:rtl"> יוצקים אלקטרוליט המימי ניטראלי לצלחת פטרי (פלואוריד למשל 1 M נתרן (NAF) או 1 M נתרן כלורי (NaCl)) לרמה שמטביעה מתכת. הערה: השימוש בחומצי (pH &lt;3) או פתרון בסיסי (pH&gt; 10) יגרום תחמוצת לפזר באופן ספונטני. </li><li style=";text-align:right;direction:rtl"> מניחים חוטי נחושת למתכת הנוזלית לפעול כאלקטרודה עבודה, וחוט ביצוע (למשל, נחושת) לאלקטרוליט לפעול כהאלקטרודה הנגדית. </li><li style=";text-align:right;direction:rtl"> חבר את החוטים למקור מתח ולהחיל פוטנציאל שלילי למתכת הנוזלית. החל כ -1 V כדי להסיר את משטח תחמוצת ולגרום המתכת לdewet מהמצע. המתכת צריכה dewet בצד הקרוב להאלקטרודה הנגדית. </li><li style=";text-align:right;direction:rtl"> החל פוטנציאלים שליליים יותר (&lt;-1 V) כדי להסיר את שכבת תחמוצת לחלוטין. הימנע החלת excesמתח שלילי גדול בלעדית על מנת למנוע בועות מימן מלהופיע במתכת הנוזלית בשל הפחתה של אלקטרוליט. </li></ol></li></ol> מדידת מתח 2. שטח באמצעות נייחים אגל <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> באמצעות חותך לייזר או כלי כרסום, לחתוך נתיב ישיר מהמרכז לקצה של פיסת polymethylmethacrylate (PMMA) (~ 1 מ&quot;מ עובי) לא לחתוך את הנתיב לאורך כל דרך העובי של PMMA.; לחתוך על רק באמצע. קטע זה ישמש כמצע למתכת הנוזלית. חומרים אחרים שטוחים ובידוד חשמלי כגון זכוכית, קרמיקה, או פולימרים יכולים לשמש גם כמצע. </li><li style=";text-align:right;direction:rtl"> עם אותו הכלי, לחתוך 1 מ&quot;מ 2 חור במרכז של PMMA. </li><li style=";text-align:right;direction:rtl"> שימוש בנתיב כמדריך, לרוץ חוטי נחושת מבודדים עם רק הקצה החשוף למרכז PMMA. מקם את החוט כך שהוא בולט מעל פני שטח PMMA. חותם את החוט במקום עם דבק leakproof. גְזִירָההחוט רק מעל פני השטח של PMMA, אבל אל תתנו לזה להאריך יותר מדי (מעבר ~ 100 מיקרומטר) או שזה יפריע את הצורה של הטיפה. </li><li style=";text-align:right;direction:rtl"> סרט החתיכה למטה PMMA לתוך מיכל שקוף שדרכו ניתן לקבל תמונה ברורה. מלא את המכל עם 1 M NaOH, ולמקם את ירידת 25-50 μl של מתכת נוזלית על חוטי נחושת הבולטות. חוט זה ישמש כהאלקטרודה העבודה ולהרטיב את הטיפה. </li><li style=";text-align:right;direction:rtl"> הנח האלקטרודה נגדית רשת פלטינה וכסף / כלוריד כסף רווי אלקטרודה התייחסות (Ag / AgCl) בפתרון. לחבר את כל האלקטרודות לpotentiostat. </li><li style=";text-align:right;direction:rtl"> מניחים את המכל במד זוית זווית מגע, כך שהפרופיל של ירידת פני השטח הוא נראה בבירור. השתמש בpotentiostat לשלוט המתח ביחס לאלקטרודה ההתייחסות, ולהשתמש במד זוית למדוד את הצורה ובכך מתח interfacial של הירידה. ודא שהמד זוית מסוגל tensi interfacial ירידה הנייח מדידהעַל; אפשר גם להשתמש בניתוח צורת axisymmetric המותאם אישית של תמונות שנלקחו מירידת מצלמה התקנה אופקית 25. </li></ol> 3. הזרקת נימים <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> מלא נימי זכוכית עם תמיסה של 1 M NaOH. קוטר הנימים צריך להיות ~ 1 מ&quot;מ. </li><li style=";text-align:right;direction:rtl"> מניחים בקצה אחד של רצף הנימים נגד ירידה של מתכת נוזלית. יישר את הנימים, כך שהוא מקביל עם המשטח של השולחן (כלומר, בניצב לכוח המשיכה). למנוע פערי אוויר בין ירידת המתכת הנוזלית ונימים מלאות אלקטרוליט. באמצעות לנגב, להספיג את כל האלקטרוליטים עודפים שאולי דלפו במהלך הרכבה. </li><li style=";text-align:right;direction:rtl"> מניחים חוטי נחושת (אלקטרודה עבודה) במתכת הנוזלית, והאלקטרודה נגדי מוליך (חוט נחושת למשל) בקצה הפתוח של נימים, כך שקשר זה הפתרון. </li><li style=";text-align:right;direction:rtl"> חבר את החוטים למקור מתח ולהחיל פוטנציאל חיובי למתכת הנוזלית. המתכת הנוזלית צריכה להתחיל למלא את גapillary (להימנע פוטנציאלים גדולים שיגרמו היווצרות בועה עודפת על האלקטרודה הנגדית). </li></ol> 4. נימי נסיגה <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> להשתמש בטכניקות דפוס ליתוגרפי 26 והעתק רכים לפברק ערוצי microfluidic מורכבים מpolydimethylsiloxane (PDMS). לפברק ערוצים שהם רחבים כ -100 עד 1,000 מיקרומטר, 100 מיקרומטר גבוהים, ו25-65 מ&quot;מ ארוך. הערה: ערוץ ממדי 1,000 מיקרומטר הרחב, 100 מיקרומטר גבוה, וערוץ 65 מ&quot;מ ארוך הניב תוצאות עקביות, אבל אחרים יכולים גם לעבוד. לחלופין, להשתמש בנימי זכוכית (למשל, בקוטר 1 מ&quot;מ זכוכית בורוסיליקט,) במקום microchannels PDMS. </li><li style=";text-align:right;direction:rtl"> הזרק מתכת נוזלית באופן ידני או באמצעות משאבת מזרק כדי למלא את הערוץ לחלוטין (כלומר, 6.5 מ&quot;מ 3 לערוץ ארוך 1,000 מיקרומטר רחב, 100 מיקרומטר גבוה, ו 65 מ&quot;מ). </li><li style=";text-align:right;direction:rtl"> באמצעות מקלון צמר גפן שנטבל ב1 M NaOH או 1 M HCl, להסיר כמויות עודפות של לילירות מתכת מהכניסה (ואם יש צורך, השקע) של הערוץ, כך שהמתכת נשארה מיושר עם פני השטח העליונים של PDMS. </li><li style=";text-align:right;direction:rtl"> לצלול קצה אחד של הערוץ באלקטרוליט (למשל, 1 M NaCl), ולמקם את האנודה (למשל, חוטי נחושת, פלטינה, או טונגסטן) כך שהוא נוגע באלקטרוליט אבל לא המתכת. </li><li style=";text-align:right;direction:rtl"> בקצה השני של הערוץ, פנה אלקטרודה נפרדת (למשל, חוט Cu) למשטח המתכת, כך שנוזל מתכת עצמה פועלת כקתודה. </li><li style=";text-align:right;direction:rtl"> חבר החוטים האלה (כלומר, האנודה וקתודה) למקור מתח או potentiostat, ולהשלים את המעגל החשמלי. למערכת שלוש אלקטרודה, למקם את האלקטרודה ההתייחסות כזו שבקושי מטביע לירידה של אלקטרוליט. </li><li style=";text-align:right;direction:rtl"> לפני יישום מתח צמצום, הר מצלמת וידאו על חצובה או במיקרוסקופ כדי להקליט את הניסויים. השתמש במצב פוקוס אוטומטי כדי לקבל את כל מה בפוקוס. לנצל פוקוס ידני יש שליטה טובה יותר עלעומק שדה, איזון לבן, ו- ISO. במידת צורך, להשתמש בתחנה גבוהה יותר F (כלומר, 11 או גבוהים יותר), 1/100 צמצם ה, איזון לבן אוטומטי ו- ISO האוטומטית. </li><li style=";text-align:right;direction:rtl"> להתחיל להקליט את הניסוי. החל כ -1 V למשוך את המתכת הנוזלית מmicrochannels. כבה את המתח לגרום המתכת להפסיק לנוע באלקטרוליט הניטרלי. </li></ol>

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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrahigh+contrast+light+valve+driven+by+electrocapillarity+of+liquid+gallium.">Ultrahigh contrast light valve driven by electrocapillarity of liquid gallium.</a> Appl. Phys. Lett. 95 (25), 251110 (2009).</li><li>Khan, M. R., Trlica, C., Dickey, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recapillarity:+Electrochemically+Controlled+Capillary+Withdrawal+of+a+Liquid+Metal+Alloy+from+Microchannels.">Recapillarity: Electrochemically Controlled Capillary Withdrawal of a Liquid Metal Alloy from Microchannels.</a> Adv. Funct. Mater. 25 (5), 671-678 (2015).</li><li>Saltman, W., Nachtrieb, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Electrochemistry+of+Gallium.">The Electrochemistry of Gallium.</a> J. Electrochem. Soc. 100, 126-130 (1953).</li><li>Perkins, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anodic-Oxidation+of+Gallium+in+Alkaline-Solution.">Anodic-Oxidation of Gallium in Alkaline-Solution.</a> J. Electroanal. Chem. 101, 47-57 (1979).</li><li>Xu, Q., Oudalov, N., Guo, Q., Jaeger, H. M., Brown, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+oxidation+on+the+mechanical+properties+of+liquid+gallium+and+eutectic+gallium-indium.">Effect of oxidation on the mechanical properties of liquid gallium and eutectic gallium-indium.</a> Phys. Fluids. 24, 063101 (2012).</li><li>Rotenberg, Y., Boruvka, L., Neumann, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+surface+tension+and+contact+angle+from+the+shapes+of+axisymmetric+fluid+interfaces.">Determination of surface tension and contact angle from the shapes of axisymmetric fluid interfaces.</a> J. Colloid Interface Sci. 93, 169-183 (1983).</li><li>Xia, Y., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Soft+Lithography.">Soft Lithography.</a> Annu. Rev. Mater. Sci. 28 (1), 153-184 (1998).</li><li>Pourbaix, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Atlas of Electrochemical Equilibria in Aqueous Solutions. , (1974).</li><li>Gough, R. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+electrocapillary+deformation+of+liquid+metal+with+reversible+shape+retention.">Rapid electrocapillary deformation of liquid metal with reversible shape retention.</a> Micro Nano Syst. Lett. 3 (1), 1-9 (2015).</li><li>Wang, M., Trlica, C., Khan, M. R., Dickey, M. D., Adams, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+reconfigurable+liquid+metal+antenna+driven+by+electrochemically+controlled+capillarity.">A reconfigurable liquid metal antenna driven by electrochemically controlled capillarity.</a> J. Appl. Phys. 117 (19), 194901 (2015).</li></ol>

The authors have nothing to disclose.

<html> שיטה זו שולטת במתח של מתכות נוזליים מבוסס גליום באמצעות מתח קטן לנהוג בתצהיר והסרת משטח תחמוצת פני השטח. למרות שהשיטה עובדת רק בפתרונות אלקטרוליט, זה פשוט, ועובד במגוון רחב של מצבים שונים, אבל יש דקויות ראוי לציין. בהיעדר הפוטנציאל חשמלי, שתי תמיסות החומציות והבסי?...

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

שליטה מתח interfacial היא שיטה יעילה לטיפול בצורה, מיקום, והזרימה של נוזלים בסולמות אורך תת מילימטר, שבו מתח interfacial הוא כוח דומיננטי. מגוון שיטות קיימות לשליטה במתח interfacial של נוזלים מימיים ואורגניים בקנה מידה זה; עם זאת, טכניקות אלה כלי למתכות נוזליים מוגבלות בשל מתח interfacial הגדול שלהם. מתכות נוזליים יכולות ליצור רכיבים רכים, מתיחה, וצורה-reconfigurable במכשירים אלקטרוניים ואלקטרו-מגנטיים. למרות שניתן לתפעל נוזלים אלה באמצעות שיטות מכאניות (למשל, שאיבה), שיטות חשמליות קלות יותר למזער, שליטה, וליישם. עם זאת, רוב טכניקות חשמל האילוצים שלהם: הרטבה חשמלית-על-דיאלקטרי דורשת פוטנציאלים גדולים (ק) להפעלה ללא צנועה, electrocapillarity יכול להשפיע על שינויים קטנים יחסית במתח interfacial, וele הרציףctrowetting מוגבל לתקעים של המתכת הנוזלית בנימים. כאן, אנו מציגים שיטה לactuating גליום וסגסוגות מתכת נוזלית מבוסס גליום באמצעות תגובת משטח אלקטרוכימיים. שליטה הפוטנציאל אלקטרוכימי על פני השטח של המתכת הנוזלית באלקטרוליט במהירות והפיך משנה את מתח interfacial על ידי יותר משני סדרי הגודל (̴500 MN / מ &#39;כמעט לאפס). יתר על כן, שיטה זו דורשת רק פוטנציאל מאוד צנוע (&lt;1 V) מיושם ביחס לאלקטרודה דלפק. השינוי וכתוצאה מכך המתח נובע בעיקר מהתצהיר אלקטרוכימיים של שכבת תחמוצת פני השטח, הפועל כחומרים פעילי שטח; הסרת תחמוצת מגבירה את מתח interfacial, ולהיפך. טכניקה זו יכולה להיות מיושמת במגוון רחב של אלקטרוליטים ואינו תלוי במצע שעליו הוא מונח.

איור 1 מציג דוגמא של טכניקת שתי אלקטרודות הפשוטה לחמצון והפחתה. במקרה זה, ירידה של 70 μl של המתכת הנוזלית להציב 1 מגעים M NaOH פתרון חוטי נחושת כדי ליצור חיבור חשמלי. M NaOH 1 מסיר את משטח תחמוצת מהמתכת ומאפשר למתכת חרוז עד בשל מתח interfacial. ?...

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

שיטה למניפולציות מתח פנים של מתכת נוזלית באמצעות חמצון פני שטח והפחתה

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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15.2K Views.  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.

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

Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow

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This manuscript highlights the experimental techniques, work-up, and analysis towards affecting the existing stable radical nature in the carbon structures. It is hoped that it will help towards further development and understanding of these interactions in the community at large.

Stable radicals that are present in carbon substrates interact with paramagnetic oxygen through a Heisenberg spin exchange. This interaction can be significantly reduced under STP conditions by flowing a diamagnetic gas over the carbon system. This manuscript describes a simple method to characterize the nature of those radicals.

היכרות עם הטבע הרדיקלי של משטח פחמן על ידי אלקטרונים פאראמגנטיים תהודה ומכוילת גז Flow

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Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

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Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

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The lack of a well-defined procedure that consistently cleaned coupon surfaces was identified as the major contributor to low and variable recoveries in cleaning verification. This manuscript describes the correct protocol of cleaning stainless steel coupons.

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Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. However, the main issue limiting their applicability is their poor stability in humid conditions. The common methods to overcome this problem involve the formation of strong metal-linker bonds by using highly charged metals, which is limited to a number of structures, the introduction of alkylic groups to the framework by post-synthetic modification (PSM) or chemical vapour deposition (CVD) to enhance overall hydrophobicity of the framework. These last two usually provoke a drastic reduction of the porosity of the material. These strategies do not permit to exploit the properties of the MOF already available and it is imperative to find new methods to enhance the stability of MOFs in water while keeping their properties intact. Herein, we report a novel method to enhance the water stability of MOF crystals featuring Cu2(O2C)4&#160;paddle-wheel units, such as HKUST (where HKUST stands for Hong Kong University of Science &#38; Technology), with the catechols functionalized with alkyl and fluoro-alkyl chains. By taking advantage of the unsaturated metal sites and the catalytic catecholase-like activity of CuII ions, we are able to create robust hydrophobic coatings through the oxidation and subsequent polymerization of the catechol units on the surface of the crystals under anaerobic and water-free conditions without disrupting the underlying structure of the framework. This approach not only affords the material with improved water stability but also provides control over the function of the protective coating, which enables the development of functional coatings for the adsorption and separations of volatile organic compounds. We are confident that this approach could also be extended to other unstable MOFs featuring open metal sites.

Robust functional catechol coatings were produced in one step by direct reaction of the material known as HKUST with synthetic catechols under anaerobic conditions. The formation of homogeneous coatings surrounding the entire crystal is ascribed to the biomimetic catalytic activity of Cu(II) dimers on the external surface of the crystals.

Functionalization פני השטח של מסגרות מתכת-אורגנית להתנגדות לחות משופר

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

מאפייני משטח של פחמן Nanoporous מסונתז סיליקה מטריצות

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 &#181;g/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

A facile protocol is presented to functionalize the surfaces of nanodiamonds with polydopamine.

שינוי בהשראה ביו השטח Polydopamine של Nanodiamonds והצמצום שלה של סילבר חלקיקים

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a ...

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part of the Properties of Actinides under Extreme Conditions laboratory (PAMEC), allows the preparation of films and studies of sample surfaces using surface analytical techniques such as X-ray and ultra-violet photoemission spectroscopy (XPS and UPS, respectively). All studies are made in situ, and the films, transferred under ultra-high vacuum from their preparation to an analyses chamber, are never in contact with the atmosphere. Initially, a film of UO2 is prepared by direct current (DC) sputter deposition on a gold (Au) foil then oxidized by atomic oxygen to produce a UO3 film. This latter is then reduced with atomic hydrogen to U2O5. Analyses are performed after each step involving oxidation and reduction, using high-resolution photoelectron spectroscopy to examine the oxidation state of uranium. Indeed, the oxidation and reduction times and corresponding temperature of the substrate during this process have severe effects on the resulting oxidation state of the uranium. Stopping the reduction of UO3 to U2O5 with single U(V) is quite challenging; first, uranium-oxygen systems exist in numerous intermediate phases. Second, differentiation of the oxidation states of uranium is mainly based on satellite peaks, whose intensity peaks are weak. Also, experimenters should be aware that X-ray spectroscopy (XPS) is a technique with an atomic sensitivity of 1% to 5%. Thus, it is important to obtain a complete picture of the uranium oxidation state with the entire spectra obtained on U4f, O1s, and the valence band (VB). Programs used in the Labstation include a linear transfer program developed by an outside company (see Table of Materials) as well as data acquisition and sputter source programs, both developed in-house.

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

This protocol presents the preparation of U2O5 thin films obtained in situ under ultra-high vacuum. The process involves oxidation and reduction of UO2 films with atomic oxygen and atomic hydrogen, respectively.

U2O5 הסרט הכנה באמצעות התצהיר2 אז פרט להתמחות על ידי זרם ישיר Sputtering וחמצון רצופים וצמצום עם אטומי חמצן ומימן אטומי

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part ...