Supporting Information
Bioinspired TiO2 Nanostructure Films with Special Wettability and
Adhesion for Droplets Manipulation and Patterning
Yuekun Lai1,2*, Yuxin Tang3, Jianying Huang2, Fei Pan1, Zhong Chen3, Keqin Zhang2,
Harald Fuchs1 & Lifeng Chi1*
1
Physikalisches Institute and Center for Nanotechnology (CeNTech), Westfälische Wilhelms-
Universität Münster, Münster D-48149, Germany, 2National Engineering Laboratory of
Modern Silk, and College of Textile and Clothing Engineering,Soochow University, Suzhou
215123, PR China, 3School of Materials Science and Engineering, Nanyang Technological
University, 50 Nanyang Avenue, Singapore 639798, Singapore
Correspondence and requests for materials should be addressed to L.F.C. (Chi@unimuenster.de) or Y.K.L. (laiy@uni-muenster.de)
Supporting movie and figure captions:
Movie S1. Superoleophobic and superaerophobic performance of the superamphiphilic
surfaces in water.
Movie S2. The dynamic stability of the anti-oil strider fabricated by the as-prepared
superamphiphilic ATP plate floating at the oil/water interface.
Movie S3. The process of on-demand underwater manipulation of an oil droplet (1,2dichloroethane) by a pair of superoleophobic tweezers in water.
Movie S4. The typical oil droplet transportation process based on the extreme high adhesion
contrast of underwater superoleophobic surface.
Movie S5. Water/oil separation by using PFDS-modified ATP plate (superoleophobic in air
and superoleophilic underwater) as an “oil capture hand” to gather oil droplets in water.
Movie S6. High selective hexadecane surface assembling on the patterned superoleophobic
ATP film by a simple dipping process.
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Figure S1. (a) FTIR spectra and (b) corresponding enlarge FTIR spectra of the as-prepared
TNB powder with and without PFDS modification.
Figure S2. The process of on-demand underwater manipulation of an oil droplet (heavier than
water) by a pair of superoleophobic tweezers in water.
Figure S3. Underwater oil droplets transportation by taking advantage of the extreme high
adhesion contrast between two superoleophobic surfaces (top one is 5 min anodizing sample,
bottom one is 240 min anodizing sample) in water.
Figure S4. XPS survey spectra (a) of the hierarchical pinecone-like structure ATP surface
before (1) and after PFDS modification (2), following UV irradiation (3); (b), (c), and (d) are
corresponding high resolution XPS spectra of F1s, C 1s, and Si 2s.
Figure S5. Optical image of patterned superoleophobic ATP surface before and after
hexadecane assembly. The pattern can be reversibly erased and regenerated by ethanol
washing and hexadecane dipping.
Figure S6. Fluorescence microscope image of the self-assembly of fluorescein sodium probes
in ethylene glycol on patterned superamphiphobic ATP surface.
Figure S7. (a,b) SEM image of Cu nanoparticle pattern based on the patterned
superoleophobic ATP surface. High magnified SEM image of the superoleophilic region (c)
and superoleophobic region (d).
2
Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical
structure of the as-prepared ATP with or without PFDS modification. Figure S1 presents the
FTIR spectra of the as-prepared TNB powder before and after the PFDS decoration. The wide
absorption bank centered at about 3380 cm-1 is due to Si-OH or Ti-OH residues on the
hydroxylated surface. In the case of the PFDS modification, additional intense band at 1212
and 1242 cm-1 is attributed to the stretching vibration of C-F bonds, 1124 cm-1 is attributed to
the stretching vibration of Si-O bonds, whereas the bans at 1146 cm-1 is characteristic for the
formation of Si-O-C bonds (M. Peng, Z. J. Liao and Z. Zhou, Langmuir, 2010, 26, 13572; V.
Georgakilas, A. B. Bourlinos, R. Zboril and C. Trapalis, Chem. Mater., 2008, 20, 2884).
Figure S1. (a) FTIR spectra and (b) corresponding enlarge FTIR spectra of the as-prepared
TNB powder with and without PFDS modification.
In order to manipulate an oil droplet in water, a pair of tweezers was thus fabricated
consisting of two superoleophobic ATP plates on the tips (Figure S2a). We built a
superoleophobic system consisting of a pair of oil-repellent tweezers utilizing the same
superoleophobic ATP plates mentioned above. Owing to excellent superoleophobic and low
adhesive properties of hierarchical structured surfaces, the oil droplet (dyed with pink)
exbhited a spherical shape (Figure S2a). The oil droplet could be held intacty and lifted from
the bottom superoleophobic substrate after the superoleophobic tweezers reached and closed
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their tips (Figure S2b). Through these tweezers moving, stopping and opening their tips, the
droplet could be placed precisely on another superoleophobic substrate without oil
contamination due to a thin water layer between the oil and superhydrophilic substrate (Figure
S2b,c) and following captured by the superoleophilic substrate (Figure S2d,e) to achieve the
on-demand manipulation of oil droplets in water.
Figure S2. The process of on-demand underwater manipulation of an oil droplet (1,2dichloroethane) by a pair of superoleophobic tweezers in water. Each image shows a
photograph of the experiment representing that stage of the droplet motion. The oil droplet
can be moved from left to right without adhesive spots left. (a) An oil droplet (dyed pink) was
carefully placed on the superoleophobic plate. (b) The tweezers held and lifted the oil droplet
away from the substrate and moved in water. (c) The tweezers released the oil droplet by
opening their tips. (d-e) The oil droplet was further transferred by superoleophobic tweezers
and captured by superoleophilic plate.
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Surface structures and roughness have a great effect on oil wettability and adhesion at
the oil/water/solid three-phase interface. Herein, we describe a simple fabrication procedure
for creating artificial hierarchical microprotrusions with nanoflakes on titanium substrates that
allows an effective, precise control of the interfacial adhesion and surface wettabiltiy in air or
underwater. By adjusting the anodizing time to control the topographical morphology and the
critical height and size of the protrusions, it is possible to create hierarchical superoleophobic
surfaces with various wettability and adhesion. Thus, the hierarchical superhydrophobic
surfaces proposed and fabricated in this study are promising for mimicking either lotus leaves
with low adhesion or rose petals with high adhesion. It is expected that such special
superhydrophobic ATP with controllable adhesion to water/oil in air or underwater will have
many potential applications, such as liquid transportation without loss and micro-fluidic
channels with diminished resistance.
In the previous section, it was shown that 3D rough ATP substrates with special
wettability (low adhesive superoleophobicity) can be applied for mechanical hand to
manipulate oil drops underwater. In this section, we realized a structure-regulated oil adhesion
switching with a high contrast on superhydrophobic ATP surfaces, by which water droplets
could be rapidly adhered, stably transferred and precisely released at targeted places (Figure
S3). In brief, first, a superoleophobic plate with high adhesive surface is approaching to
contact and catch the oil droplet on superoleophobic surface with ultralow adhesion. In the
following, the plate with adhered oil droplet moves and releases the oil droplet to the targeted
place in water. Furthermore, we demonstrate the implementation of four basic functionalities
that are critical for any on demand microfluidic devices based on oil droplet manipulation:
transfer, splitting, mixing and collection. The complete list of possible functionalities is
certainly longer, especially when more complex manipulation processes are considered.
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Figure S3. Typical oil droplet transportation process based on the extreme high adhesion
contrast of the underwater superoleophobic surface. By taking advantage of the extreme high
adhesion contrast, oil droplets can be transferred from low adhesive superoleophobic surface
to high adhesive superoleophobic surface in water (a, b) following to release on the target
oleophilic places (c, d).
X-ray photoelectron spectroscope (XPS) was used to confirm the surface component
change of the ATP surface after PFDS modification and UV irradiation. The results
demonstrate the existence of element Ti, O, Si, C and some traces of fluorine on the surface
(Figure S4a). The presence of the strong F 1s peak and C 1s peak (due to C-F), together with
the Si 2p appearance and attenuation of the Ti 2p and Ti 2s peaks confirm that PFDS has been
successfully self-assembled onto the pinecone-like ATP surface (Figure S4a,b). Another
obvious character of the presence of PFDS monolayer is the large intensity increase of the F
1s peak at 689.0 eV and the sharp intensity decrease of the F 1s at 684.4 eV (Figure S4b). The
main peak corresponding to CFx indicates that the PFDS coating on the outermost surface
while the metal fluoride peak at 684.4 eV is due to the anion uptake into the oxide layers
during the anodizing process in fluoride containing solution. However, when UV light
irradiate the PFDS modified ATP film, the F 1s peak at 689.0 eV and Si 2p peak are greatly
weakened (Figure S4b) while a stronger C-H peak at 284.8 eV appears (Figure S4c).
Therefore, it is reasonable to conclude that the low surface energy fluorocarbon group has
been degraded by the photocatalytic activity of ATP film under UV light illumination. Such
surface chemical component change play vital role for the wettability response of the
corresponding surfaces.
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Figure S4. (a) XPS survey spectra of the hierarchical pinecone-like structure ATP surface
before (1) and after PFDS modification (2), following UV irradiation (3); (b), (c), and (d) are
corresponding high resolution XPS spectra of F1s, C 1s, and Si 2s.
The pattern can be reversibly erased and regenerated for many cycles by rapid ethanol
washing (Figure S5a) and hexadecane dipping (Figure S5b). This is primarily attributed to
the excellent patterned superoleophobic ATP film with good dynamic stability and high
wettability contrast.
Figure S5. Optical image of patterned superoleophobic ATP surface before and after
hexadecane surface assembling. The scale bar is 5 mm.
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Based on the high contrast wettability template, various well-defined surface patterns
were constructed on the patterned superoleophobic ATP surface, such as liquid micro-droplets,
semiconductor and metal nanoparticles, fluorecent probes in a highly selective manner. In a
proof-of-concept study, we prepared fluorescein sodium probes (Figure S6) and Cu
nanoparticles (Figure S7) on patterned superoleophobic ATP surface to obtain well defined
fluorescent pattern by a simple immersion process and Cu@ATP surface pattern by a rapid
electrochemical deposition process (2 min). It can be seen that fluorescent probes and Cu
nanoparticles are high selective to self-assembly and deposit on superoleophilic regions due to
the rough structure for air trapping and low surface energy chemicals to resist wetting. We
envision such 3D functional surface patterns would be a versatile platform in a wide range of
applications, especial for biomedical devices (e.g., high-throughput molecular sensing,
targeted antibacterial and drug delivery).
Figure S6. Fluorescence microscope image of the self-assembly of fluorescein sodium probes
in ethylene glycol on patterned superamphiphobic ATP surface.
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Figure S7. (a,b) SEM image of Cu nanoparticle pattern based on the patterned
superoleophobic ATP surface. High magnified SEM image of the superoleophilic region (c)
and superoleophobic region (d).
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