Department of Life Science, University of Seoul, Seoul, 130-743, Republic of Korea.
Department of Mechanical Engineering, Sogang University, Seoul, 121-742, Republic of Korea.
Small. 2018 Nov;14(45):e1803055. doi: 10.1002/smll.201803055. Epub 2018 Oct 7.
Controlled assembly of colloidal nanoparticles onto solid substrates generally needs to overcome their thermal diffusion in water. For this purpose, several techniques that are based on chemical bonding, capillary interactions with substrate patterning, optical force, and optofluidic heating of light-absorbing substrates are proposed. However, the direct assembly of colloidal nanoparticles on generic substrates without chemical linkers and substrate patterning still remains challenging. Here, photothermal convection lithography is proposed, which allows the rapid placement of colloidal nanoparticles onto the surface of diverse solid substrates. It is based on local photothermal heating of colloidal nanoparticles by resonant light focusing without substrate heating, which induces convective flow. The convective flow, then, forces the colloidal nanoparticles to assemble at the illumination point of light. The size of the assembly is increased by either increasing the light intensity or illumination time. It is shown that three types of colloidal gold nanoparticles with different shapes (rod, star, and sphere) can be uniformly assembled by the proposed method. Each assembly with a diameter of tens of micrometers can be completed within a minute and its patterned arrays can also be achieved rapidly.
胶体纳米粒子在固体基底上的可控组装通常需要克服其在水中的热扩散。为此，提出了几种基于化学键合、与基底图案化的毛细相互作用、光镊和光吸收基底的光流体制动的技术。然而，在没有化学连接体和基底图案化的情况下，将胶体纳米粒子直接组装在通用基底上仍然具有挑战性。在这里，提出了光热对流光刻技术，它允许胶体纳米粒子快速放置在各种固体基底的表面上。它基于胶体纳米粒子的局部光热加热通过共振光聚焦而不加热基底，这会引起对流。然后，对流迫使胶体纳米粒子在光的照射点处组装。通过增加光强度或照射时间，可以增加组装的尺寸。结果表明，通过所提出的方法可以均匀地组装三种不同形状（棒状、星状和球状）的胶体金纳米粒子。每个直径数十微米的组装可以在一分钟内完成，其图案化的阵列也可以快速实现。
