In order to test whether this superhydrophobicity
was kept after abrasion on the whole area but not
merely on some points (contact angle measuring
points), water droplet was guided by a needle to
travel on the PDT glass surface after the 11th, 20th,
30th, and 40th cycle’s abrasion, respectively (movie
S12). The water droplet traveling after the 40th
cycle is shown in Fig. 4D.
To enlarge the application scale and broaden the
types of substrates, the spray adhesive [EVO-STIK
(Bostik, UK)] was also used to bond glass, steel,
cotton wool, and filter paper substrates with the
superhydrophobic paint. We show in fig. S10 and
movie S13 the finger-wipe tests on untreated, paint-treated, and “paint + spray adhesive”–treated
(PSAT) substrates, respectively. On hard substrates
(glass and steel), PSAT surfaces retained water
proofing, whereas the paint was just removed
when directly applied; the case is different on
soft substrates (cotton and paper), on which paint
was protected by their porous structures, resulting
in both paint-treated and PSAT cotton and paper
being superhydrophobic after the finger-wipe.
However, in a more powerful test (sandpaper
abrasion of cotton), this “protection” is limited
(fig. S11). As shown in fig. S12 and movie S14, the
sandpaper abrasion tests on PSAT substrates and
both hard and soft substrates became robust after
the PSAT treatment. As shown in fig. S13 and
movie S15, the PSAT substrates retained water
repellency after knife-scratch tests. After different
damages, the PSAT materials still remained superhydrophobic, indicating that this method
could efficiently enhance the robustness of superhydrophobic surfaces on different substrates; it is
believed that the idea of “superhydrophobic paint +
adhesives” can be simply, flexibly, and robustly
used in large-scale industrial applications.
The superhydrophobic surfaces show that a
robust resistance to oil contamination and ease
of applicability can be achieved by implementing
straightforward coating methods such as spraying, dip-coating, or even simply extrusion from a
syringe. The flexibility of the “paint + adhesives”
combination enables both hard and soft substrates to become robustly superhydrophobic and
self-cleaning. The surfaces can be readily implemented in harsh and oily environments where
robustness is required.
REFERENCES AND NOTES
1. W. Barthlott, C. Neinhuis, Planta 202, 1–8 (1997).
2. R. Blossey, Nat. Mater. 2, 301–306 (2003).
3. I. P. Parkin, R. G. Palgrave, J. Mater. Chem. 15, 1689 (2005).
4. T. Onda, S. Shibuichi, N. Satoh, K. Tsujii, Langmuir 12, 2125–2127
5. L. Feng et al., Adv. Mater. 14, 1857–1860 (2002).
6. J. Zimmermann, F. A. Reifler, G. Fortunato, L. C. Gerhardt,
S. Seeger, Adv. Funct. Mater. 18, 3662–3669 (2008).
7. X. Zhu et al., J. Mater. Chem. 21, 15793 (2011).
8. Q. Zhu et al., J. Mater. Chem. A 1, 5386 (2013).
9. A. Tuteja et al., Science 318, 1618–1622 (2007).
10. X. Deng, L. Mammen, H. J. Butt, D. Vollmer, Science 335,
11. Y. Lu et al., ACS Sustainable Chem. Eng. 1, 102 (2013).
12. Materials and methods are available as supplementary
materials on Science Online.
13. D. Richard, C. Clanet, D. Quéré, Nature 417, 811 (2002).
14. J. C. Bird, R. Dhiman, H. M. Kwon, K. K. Varanasi, Nature 503,
15. Y. Lu et al., J. Mater. Chem. A 2, 12177 (2014).
16. D. Vella, L. Mahadevan, Am. J. Phys. 73, 817 (2005).
17. A. Tuteja, W. Choi, J. M. Mabry, G. H. McKinley, R. E. Cohen,
Proc. Natl. Acad. Sci. U.S.A. 105, 18200–18205 (2008).
18. A. Nakajima et al., Langmuir 16, 7044–7047 (2000).
19. R. Fürstner, W. Barthlott, C. Neinhuis, P. Walzel, Langmuir 21,
20. B. Bhushan, Y. C. Jung, K. Koch, Langmuir 25, 3240–3248 (2009).
21. T. S. Wong et al., Nature 477, 443–447 (2011).
22. M. Nosonovsky, Nature 477, 412–413 (2011).
23. A. Grinthal, J. Aizenberg, Chem. Mater. 26, 698–708
24. D. C. Leslie et al., Nat. Biotechnol. 32, 1134–1140 (2014).
25. M. Im, H. Im, J. Lee, J. Yoon, Y. Choi, Soft Matter 6, 1401 (2010).
26. B. Wang et al., ACS Appl. Mater. Interfaces 5, 1827–1839 (2013).
We thank M. Vickers and S. Firth for XRD and TEM characterizations.
Thanks to C. E. Knapp and D. S. Bhachu for ordering chemicals and
the help with some experiments.
Materials and Methods
Figs. S1 to S13
References (27, 28)
Movies S1 to S15
16 October 2014; accepted 30 January 2015
Single-protein spin resonance
Fazhan Shi,1,2,3 Qi Zhang,1,2 Pengfei Wang,1,2,3 Hongbin Sun,4 Jiarong Wang,4
Xing Rong,1,2,3 Ming Chen,1,2 Chenyong Ju,1,2,3 Friedemann Reinhard,5† Hongwei Chen,4
Jörg Wrachtrup,5 Junfeng Wang,4 Jiangfeng Du1,2,3‡
Magnetic resonance is essential in revealing the structure and dynamics of biomolecules.
However, measuring the magnetic resonance spectrum of single biomolecules has remained
an elusive goal. We demonstrate the detection of the electron spin resonance signal from a
single spin-labeled protein under ambient conditions. As a sensor, we use a single nitrogen
vacancy center in bulk diamond in close proximity to the protein. We measure the orientation
of the spin label at the protein and detect the impact of protein motion on the spin label
dynamics. In addition, we coherently drive the spin at the protein, which is a prerequisite for
studies involving polarization of nuclear spins of the protein or detailed structure analysis of
the protein itself.
Observing the structure and dynamics of single molecules is a long-sought goal that has inspired technical developments in a wide range of disciplines (1–4). As one of the most important techniques, electron
spin resonance (ESR) finds broad application for
studying basic molecular mechanisms in biology
and chemistry (5). Most proteins, however, are
nonparamagnetic and thus cannot be accessed
by the technique. Labeling biomolecules with a
small spin-bearing moiety, such as nitroxide
spin labels, enables ESR to acquire a broad
range of structural and dynamical information.
However, current methods need 1010 uniform
molecules to accumulate a large enough signal-to-noise ratio. This substantially complicates
efforts to compile structural and dynamical
information. New methods that have tried to
push the sensitivity of magnetic resonance to
the single-spin level all require either a dedicated
environment (6, 7) or conducting surfaces and
A sensor that could accomplish single-protein
detection under ambient conditions is a recently developed atomic-sized magnetic field
sensor based on the nitrogen vacancy (NV) defect
center in diamond (9–11). Because of its long coherence times (12, 13), the NV sensor can detect a
single electron spin over a distance of 30 nm
under ambient conditions. As proof-of-principle
demonstrations, single electron spins inside
diamond or on diamond surfaces have been
sensed (14–16). Despite previous efforts, single-biomolecule detection and spectroscopy have
not been attained. Here, we report an electron
spin resonance study on a single protein, which
allows us to extract the structural and dynamical
properties from spectral analysis.
As the experimental sample, we chose MAD2
(mitotic arrest deficient-2), an essential spindle
SCIENCE sciencemag.org 6 MARCH 2015 • VOL 347 ISSUE 6226 1135
1Hefei National Laboratory for Physical Sciences at the
Microscale and Department of Modern Physics, University of
Science and Technology of China (USTC), Hefei 230026,
China. 2Joint Laboratory of Quantum Biophysics, USTC
Institute of Biophysics and Chinese Academy of Sciences.
3Synergetic Innovation Center of Quantum Information and
Quantum Physics, USTC, Hefei 230026, China. 4High
Magnetic Field Laboratory, Chinese Academy of Sciences,
Hefei 230000, China. 53rd Physics and Integrated Quantum
Science and Technology (IQST), University of Stuttgart,
70569 Stuttgart, Germany.
*These authors contributed equally to this work. †Present address:
Walter Schottky Institut, E24, Technische Universität München,
85748 Garching, Germany. ‡Corresponding author. E-mail: djf@
RESEARCH | REPORTS