<br>表面活性剂对碳纳米管悬浮液中咖啡环形成的控制,Langmuir

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表面活性剂对碳纳米管悬浮液中咖啡环形成的控制
Langmuir ( IF 3.7 ) Pub Date : 2023-01-06 , DOI: 10.1021/acs.langmuir.2c01691
N S Howard ₁ , A J Archer _{2,

3} , D N Sibley _{2,

3} , D J Southee ₄ , K G U Wijayantha _{1,

5}

Affiliation

咖啡环效应在胶体液滴蒸发过程中经常发生，并且通常是不希望的。在这里，我们表明添加特定浓度的表面活性剂可以减轻这种影响。我们对碳纳米管的水悬浮液进行了实验，该悬浮液是用阳离子表面活性剂十二烷基三甲基溴化铵以临界胶束浓度的0.2、0.5、1、2、5和10倍添加来制备的。将胶体液滴沉积在具有不同润湿特性的印刷电子候选基材上：玻璃、聚对苯二甲酸乙二醇酯、氟乙烯丙烯共聚物和聚二甲基硅氧烷。干燥后，在最终沉积物中观察到四种图案类型：点状、均匀、咖啡环沉积物和组合图案（具有点状中央沉积物的咖啡环）。对于大多数图案类型，蒸发主要发生在恒定接触半径模式下，除了一些导致均匀沉积的情况，其中发生接触线的早期后退。图像分析和轮廓测量得出沉积物厚度，使我们能够识别所有均匀沉积物中的咖啡环子特征，并推断所有情况下的覆盖百分比。重要的是，确定了在所有基材上生成高度均匀沉积物的关键表面活性剂浓度。这种浓度导致视觉上均匀的沉积物，由咖啡环子特征和密集的中心组成，由两个不同的蒸发相产生。

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Surfactant Control of Coffee Ring Formation in Carbon Nanotube Suspensions

The coffee ring effect regularly occurs during the evaporation of colloidal droplets and is often undesirable. Here we show that adding a specific concentration of a surfactant can mitigate this effect. We have conducted experiments on aqueous suspensions of carbon nanotubes that were prepared with cationic surfactant dodecyltrimethylammonium bromide added at 0.2, 0.5, 1, 2, 5, and 10 times the critical micelle concentration. Colloidal droplets were deposited on candidate substrates for printed electronics with varying wetting characteristics: glass, polyethylene terephthalate, fluoroethylene propylene copolymer, and polydimethylsiloxane. Following drying, four pattern types were observed in the final deposits: dot-like, uniform, coffee ring deposits, and combined patterns (coffee ring with a dot-like central deposit). Evaporation occurred predominantly in constant contact radius mode for most pattern types, except for some cases that led to uniform deposits in which early stage receding of the contact line occurred. Image analysis and profilometry yielded deposit thicknesses, allowing us to identify a coffee ring subfeature in all uniform deposits and to infer the percentage coverage in all cases. Importantly, a critical surfactant concentration was identified for the generation of highly uniform deposits across all substrates. This concentration resulted in visually uniform deposits consisting of a coffee ring subfeature with a densely packed center, generated from two distinct evaporative phases.

更新日期：2023-01-06

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