ChemistryWorld報道仿生研究工作進展
http://www.rsc.org/chemistryworld/2014/08/interview-yongmei-zheng-spider-silk-water-droplet
Yongmei Zheng:
Spider silk and butterfly wings
7 August 2014
by Jennifer Newton
Yongmei Zheng is a
professor of chemistry at Beihang University in
China. Research in the Zheng group looks at biological and bioinspired surfaces
with wettability functions.
Yongmei Zheng
Who or what inspired you to become a scientist?
Nature – there is
so much we can learn from it. Biological materials have a range of unimaginable
but smart functions. It is my aim to reveal these biological phenomena to
better the lives of human beings.
Can you give me a bit more detail on your overall
research aims?
I hope to
understand the natural laws of wettability on biological and bioinspired
material surfaces. We use physical, chemical and nanotechnology methods to
fabricate bioinspired functional surfaces with unique effects resulting from
gradients in micro- and nanostructures, to find wetting mechanisms such as
water repellency or water collection. We hope to develop these properties for
possible applications.
You’ve done a lot of work trying to recreate the
properties of spider silk – why is this such an interesting material?
Shiny water droplets on a spider''''s
web
After millions of
years, many creatures have evolved ways of making filamentous fibres. These
materials have been used in all sorts of applications including fabrics,
medical wound dressings and military applications. Silks have excellent
mechanical properties and chemical compositions. Spider silks are praised as
unique natural biomaterials with characteristics at both the chemical and
physical levels. They are undoubtedly the most excellent structural and
functional materials in nature.
We discovered that
the capture silk of the cribellate spider, Uloborus
walckenaerius, collects water from air.1 Its unique micro- and nanostructure, which is
characterised by periodic spindle-knots made of random nanofibrils that are
separated by joints made of aligned nanofibrils, gives rise to a combination of
gradients to achieve this cooperative effect that drives tiny water droplets
(under 100μm in diameter) toward the spindle-knots for highly efficient water
collection.
What is your research group working on at the moment?
Our group is
working to reveal the cooperative effect of multi-gradient micro- and nanostructured
(MN) interfaces on the surface of wettable materials – for example, how to use
chemical gradients, physical gradients, geometric gradients and responsive
wettability gradients, to control droplet behaviour.
We have found that
a multi-gradient MN cooperative effect can break through unsolved problems
regarding function on material surfaces, such as condensed droplet transport,
hysteresis limitations and water repellency at low temperatures.
We are pursuing
two main research routes regarding functional materials. One is characterising
water collection in materials like spider silk by looking at droplet transport,
droplet gathering and fogdrop harvesting from air. The other is characterising
water repellency on materials like butterfly wings by looking at
superhydrophobicity, anti-icing and ice-phobic effects.
Inspired by the
role that micro- and nanostructures (MNs) play in the water collecting ability
of spider silk we have designed and made a series of fibres2 by integrating fabrication methods and
technologies, such as dip-coating, Rayleigh instability to break-up droplets
and phase separation, alongside strategies that combine electrospinning and
electrospraying, fluid-coating and wet-assembly.
Our structures can
be tailored to demonstrate the mechanism of multiple gradients in driving tiny
water droplets. Rough and smooth fibre surfaces, together with a chemical
gradient, can generate movement and control water droplets.
Ways to fabricate bioinspired fibres and
applications of bioinspired fibres with unique wettability
In the case of
larger water droplets, geometrically-engineered thin fibres have a much greater
water capturing ability than previously thought. This is due to the increased
stability of the phase contact line that combines ‘slope’ and ‘curvature’
effects on spindle-knots, providing sufficient capillary adhesion to retain the
hanging droplets. To extend this functionality, we have made bead-on-string
heterostructured fibres (BSHFs) out of poly-(methyl methacrylate) (PMMA) and
titanium tetrachloride (TiCl4) hydrolysed nanoparticles, via a one-step
electrohydrodynamic method that combines electrospinning and electrospraying
strategies. BSHFs can collect water by intelligently responding to
environmental changes in humidity. We are also developing a wet-assembly
technique that integrates electrospinning, particle fog and water condensation
to createheterostructured nanofibres.3
Can you explain where your work looking at butterfly
wings could be applied?
Butterfly wings
have multi-level oriented, anisotropic, or step-like micro- and nanostructures
on their surface to repel water in a particular direction.4 We have modelled the micro- and nanostructures of
butterfly wings to obtain a bioinspired surface. The excellent water repellency
of these bioinspired surfaces could have promising applications for controlling
droplets in micro-fluidics as self-cleaning, anti-adhesion, anti-icing and
anti-fogging surfaces.
What is the greatest challenge you face in your research
at the moment?
The greatest
challenge is developing ways to make robust and wettable materials on a large
enough scale to actually be applied.
REFERENCES
-
Y Zheng et al, Nature,
2010, 463, 640 (DOI: 10.1038/nature08729)
-
Y Chen and Y Zheng, Nanoscale,
2014, 6, 7703 (DOI: 10.1039/c4nr02064b)
-
L Zhao et al, Chem.
Commun., 2014, DOI: 10.1039/c4cc05156d
-
Liu et al, ACS
Nano, 2014, 8, 1321 (DOI: 10.1021/nn404761q); H Mei et al,Soft
Matter, 2011, 7, 10569 (DOI: 10.1039/c1sm06347b); Y Zheng et al, Soft Matter,
2007, 3, 178 (DOI: 10.1039/b612667g)