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液态Ga及其合金的熔点低、毒副作用小、导电率高,使得这类液态金属能像石墨烯一样被广泛应用于微流器件、柔性电子器件中,制备这些器件的关键在于有效控制各生产环节中液态金属在固体界面上的润湿性及形貌特征.基于Lennard-Jones(L-J)势函数,利用分子动力学模拟方法研究了金属Ga在石墨烯表面的润湿性,根据模拟结果拟合的L-J势参数能正确描述Ga原子与衬底之间的相互作用并得到了与实验值极为接近的润湿角,发现衬底与液膜间相互作用的微小改变都会对最终润湿形态产生极大影响,平衡态的润湿角和脱离衬底速度随着Ga-C间势能的减小而增大,并成功获得了不同厚度的Ga液膜在石墨烯表面的形态演变规律,极为符合液态Ga的基本特性.利用所得L-J势函数参数模拟了液态Ga在粗糙度相同但纳米柱尖端形貌不同的C材料表面的润湿演变,发现纳米柱尖端形貌对液态Ga的润湿过程及状态影响极大.
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关键词:
- 分子动力学模拟 /
- 液态镓 /
- 石墨烯 /
- Lennard-Jones势
Liquid gallium and its alloy with low melting point, low toxic and high electrical conductivity are used extensively in burgeoning microfluidic and flexible electronic devices. The key to producing these devices is to effectively control the wettability and morphology of liquid metal on the solid interface in different manufacturing processes. Based on the Lennard-Jones (L-J) potential describing the solid-liquid interaction, the wettabilities of liquid gallium film on the smooth and rough graphene surfaces are effectively investigated by molecular dynamics simulation which is an available and powerful option in this field. Different regimes of wetting are discovered by changing the depth of the L-J potential, and the stable contact angle increases with Ga-C potential depth decreases. The results show that the equilibrium contact angle and the retraction velocity increase with the decrease of the L-J potential between the gallium and graphene, showing that some properties change from complete wetting to hydrophilic and to hydrophobic. The L-J potential depth obtained from the simulation results can be effectively employed to describe the interaction between the liquid gallium and the substrate because the resulting wetting angle is extremely close to the experimental value. When employing the most appropriate L-J potential, it is found that although the initial retraction velocity increases with the proportional decrease of the thickness of the liquid Ga film, there are a few of differences in equilibrium contact angle and final retraction velocity in virtue of the competition between the surface tension of the Ga film and Ga-C interaction. It means that for the wetting state the film thickness is not the crux for changing the equilibrium contact angle and retraction velocity based on a similar conversion of potential energy into kinetic energy. Finally, we investigate the effects of the L-J potential on three rough surfaces which are patterned into three types of nanopillars with different top morphologies respectively. Specifically, it is shown that in spite of similar surface roughness, the wetting morphologies of liquid gallium deposited on various nano-textured graphene surfaces range from hydrophobic to dewetting state, suggesting that not only the roughness but also the morphology of surface can exert an available influence on the wettability of liquid. The wetting transition between the wetting and dewetting state can be achieved dynamically by adjusting the morphologies of nanopillars involved although we still need to go into more detail on the configurable way to fulfill the changing requirements.-
Keywords:
- molecular dynamics simulation /
- liquid gallium /
- graphene /
- Lennard-Jones potential
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[23] Blake T D, Clarke A J, de Coninck J, de Ruijter M J, Belgium M 1997 Langmuir 13 2164
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[26] NaidichJu J V, Chuvashov N 1983 J. Mater. Sci. 18 2071
[27] Stukowski A 2009 Model. Simul. Mater. Sci. Eng. 18 15012
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[1] Worthington A M 1876 Proc. R. Soc. 25 261
[2] Josserand C, Thoroddsen S T 2016 Annu. Rev. Fluid Mech. 48 365
[3] Nishimoto S, Bhushan B 2013 RSC Adv. 3 671
[4] Höcker H 2002 Pure Appl. Chem. 74 423
[5] Boreyko J B, Chen C H 2009 Phys. Rev. Lett. 103 184501
[6] Chu K H, Joung Y S, Enright R, Buie C R, Wang E N 2013 Appl. Phys. Lett. 102 151602
[7] Choi C H, Kim C J 2006 Phys. Rev. Lett. 96 066001
[8] Geim A K, Novoselov K S 2007 Nature Mater. 6 183
[9] Hu L, Wang L, Ding Y, Zhan S, Liu J 2016 Adv. Mater. 28 9210
[10] Ordonez R C, Yashi C K H, Torres C M, Hafner N, Adleman J R, Acosta N M, Melcher J, Kamin N M, Garmire D 2016 IEEE Trans. Electron Devices 63 4018
[11] Secor E B, Ahn B Y, Gao T Z, Lewis J A, Hersam M C 2015 Adv. Mater. 27 6683
[12] Gozen B A, Tabatabai A, Ozdoganlar O B, Majidi C 2014 Adv. Mater. 26 5211
[13] Dickey M D 2014 ACS Appl. Mater. Interfaces 6 18369
[14] So J H, Thelen J, Qusba A, Hayes G J, Lazzi G, Dickey M D 2009 Adv. Funct. Mater. 19 3632
[15] Paik J K, Kramer R K, Wood R J 2011 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS2011) San Francisco, CA, USA, 25-30 September, 2011 p414
[16] Zhang J, Yao Y Y, Sheng L, Liu J 2015 Adv. Mater. 27 2648
[17] Fuentes-Cabrera M, Rhodes B H, Fowlkes J D, López-Benzanilla A, Terrones H, Simpson M L, Rack P D 2011 Phys. Rev. E 83 041603
[18] Plimpton S 1995 J. Comput. Phys. 7 1
[19] Baskes M I, Chen S P, Cherne F J 2002 Phys. Rev. B 66 104107
[20] Lee T, Taylor C D, Lawson A C, Conradson S D, Chen S P, Caro A, Valone S M, Baskes M I 2014 Phys. Rev. B 89 174114
[21] Ren W 2014 Langmuir 30 2879
[22] de Coninck J, Blake T D 2008 Annu. Rev. Mater. Res. 38 1
[23] Blake T D, Clarke A J, de Coninck J, de Ruijter M J, Belgium M 1997 Langmuir 13 2164
[24] Bertrand E, Blake T D, de Coninck J 2009 Eur. Phys. J.: Spec. Top. 166 173
[25] Li K, He H Y, Xu B, Pan B C 2009 J. Appl. Phys. 105 054308
[26] NaidichJu J V, Chuvashov N 1983 J. Mater. Sci. 18 2071
[27] Stukowski A 2009 Model. Simul. Mater. Sci. Eng. 18 15012
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