Supporting Information
Title page
Title:
Ordering Ag nanowire arrays by spontaneous spreading of volatile
droplet on solid surface
Han Dai1, , Ruiqiang Ding1, , Meicheng Li1, 2*, Jinjer Huang3, Yingfeng Li1, and Mwenya
‡
‡
Trevor1
1
State Key Laboratory of Alternate Electrical Power System with Renewable Energy
Sources, School of Renewable Energy, North China Electric Power University, Beijing
102206, China.
2
Suzhou Institute, North China Electric Power University, Suzhou 215123, China.
3
Harbin University of Science and Technology, Harbin 150006, China.
Correspondence to Meicheng Li (mcli@ncepu.edu. cn)
‡ These authors contributed equally to this work.
Contents
1. Arrangements of Ag nanowires in the central regions
2. The orientation process of Ag nanowires
3. The influence of the length effect on the arrangement of Ag nanowires on silicon
(glass) surfaces
4. Images of the transferred Ag nanowires on the tape
1. Arrangements of Ag nanowires in the central region
Figure S1. Optical images of Ag nanowires in the central region.
The thermal convection which is more obvious in thick violate liquid could lead
circumfluence inside the liquid. Obviously, the circumfluence of the suspension
cannot order Ag nanowires on the solid surface. The thickness of the film in the
central region is largest. Obvious circumfluence can be observed in this region. Thus,
Ag nanowires in the central region shows random shaped arrangement due to the
circumfluence in the centre. Outside the central region, the circumfluence can be
suppressed by the thin suspension film.
2. The orientation process of Ag nanowires
Due to the fast movement of the mirofluid in the initial of the spreading, the
trajectory of Ag nanowires in the suspension are hard to catch. We choose the
middle stage of the spreading process which has a relatively stable mirofluid to
study the influence of the mirofluid on the orientation of Ag nanowires. During the
spreading process, the movements of Ag nanowires near the surface of the
substrate are captured using the CCD device as shown in video file S2. The
movements of Ag nanowires follow the spreading mirofluid and are ordered in the
suspension during the spreading process.
3. The influence of the length effect on the arrangement of Ag nanowires
on silicon (glass) surfaces
Based on previous studies (J. Fluid Mech. (1971), vol. 46, part 4, pp. 813-829 &J.
Fluid Mech. (1992), vol. 238, pp. 277-296), it is known that longer Ag nanowires
(the radius of Ag nanowires approximately the same) provide larger moment of
torsion which is beneficial to the orientation of Ag nanowires in suspension in a short
time. Meanwhile, due to the van der waas force between Ag nanowires and solid
surfaces, the adhesion force mainly depends on the contact area between Ag
nanowires and solid surfaces. Thus, longer Ag nanowires are more easily adhered
and ordered onto the solid surface.
However, too large aspect ratio of Ag nanowires and too high concentration of the
suspension would cause serious hydrodynamic interactions between nanowires (J.
Non-Newtonian Fluid Mech. (1997) vol.73, pp.205–239). These nanowires
interactions induce a significant amount of extra nanowire flipping which would
increase the chances of irregular arrangement of Ag nanowires along the flow
directions. Meanwhile, there are insufficient rotations of Ag nanowires which directly
adhere on solid surface as shown in Fig. 2. If Ag nanowires are too long, the
irregular adhesion of Ag nanowires can lead to serious reunion on solid surface.
Thus, the lengths of Ag nanowires on the orientation have a suitable scope. In this
work, we mainly focused on the spreading phenomena for Ag nanowires orientation.
For our future work, we intend to optimize the length of Ag nanowires for suitable
density nanowires suspension.
4. Images of the transferred Ag nanowires on the tape
Figure S2. Orientation image of Ag nanowires on the tape. (a) Optical microscopy
image of Ag nanowires on the tape (originally in the ring region); (b) Optical
microscopy image of Ag nanowires on the tape (originally in the edge region).
The orientation of Ag nanowires on the tape in a small scope is similar with that on
the solid surface. However, some bending can be found on Ag nanowires which is
caused by the pressure of Ag nanowires on roughness tape surface. This bending
could be improved by using a more smooth tape.