Cicada wings as biotemplate and their modi˜cationsiss.fzu.cz/Previous/LS2011/posters/Berger - Devet...
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Cicada wings as biotemplate and their modifications Jan Berger a , Jan Proška a , Filip Novotný a , Radek Fajgar b (a) Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Dept. of Physical Electronics, Břehová 7, 115 19 Praha 1, Czech Republic, [email protected] (b) Institute of Chemical Process Fundamentals of the ACSR, v. v. i., Rozvojová 2/135, 16502 Praha 6, Czech Republic, [email protected] Introduction Cicada (Pomponia intermedia) A C B D Cicada wing is covered with hexagonally ordered papillary. The pillars have height about 400 nm and their diameter is about 120 nm. The morphology is identical for the dorsal and ventral surfaces and be- tween male and female specimens. Structure consisting of arrays of pillars has anti-reflection function and therefore the wings are trans- parent (in broad band from approximately 450 nm to 2500 nm). Chitinous strucuture on upper side of wing shows hydrophilic prop- erties, which are increased by epicuticular waxes. Hydrophobicity can be explained by Wenzel's model or Cassie-Bexters model. The wing is appropriate template for replication and function modifications. Cutitular waxes are very important during replication because enable easier separation of negative replica from template. (A) Pomponia intermedia. (B) Large area of a dorsal side a of cicada’s wing with chitin- ous pillars. (C) Detail of array of pillars - side view. (D) Drop of water (volume of 2 micro- liters) on upper side of wing. 1 μm 200 nm A B C D Replications and nanocasting Reliefs with typical dimension in the order of ten nanometers can be replicated using the method of casng (nanocasng) into suitable polymer matrice such as PMMA or PDMS. The polymer is poured on a specially prepared surface that we want to replicate. Aſter curing, we can easily separate a negave replica in polymer from the template and manipulate with it. The polymer replica serves as the intermedi- ate template for the preparaon of self-supporng gold foil with aper- tures about 100 nm - dimension interesng for applicaons in photon- ics and as a substrate for SERS (Surface Enhanced Raman Spectros- copy). Large (macroscopic) areas can be reproduced in the high de- tails. Short heang of the gold foil (about 300°C for 15 seconds) results in uniform reducon of nanoholes diameters. F PMMA / PDMS PMMA / PDMS Template Template 2 µm 100 nm 1 μm 100 nm F E 100 nm 100 nm E Photo-controled wettability of surfaces Hydrophobic properties of the cicada wings can be further modified and used for another purposes. One way how to modify this natural material is deposition of thin layer of semiconductor oxides using ArF excimer laser ab- lation of ZnO, SnO , and TiO targets, respectively. After deposition of 5 nm of SnO on the surface of cicadas wing, we have ob- tained a substrate, which was hydrophobic. However, in the presence of water (for example air humidity) and exposure to UV radiation, a chemical reaction occurs and the wing surface become super-hydrophilic. In these inorganic oxides (ZnO, SnO , TiO ), the photogenerated formation of electron-hole pairs leading to oxygen-deficient surface sites is believed to be responsible for the effect. Hydroxyl group adsorption on the defect sites is prefered to oxygen adsorption, leading to low water contact angle. The original hydrophobic state is then restored as the hydroxyl groups are re- placed by ambient oxygen during storage in dark. Irradiation was carried out 60 minutes with UV lamp with an output 2 x 8 W at a wavelength 366 nm. G A B C D F (A) A negative replica of cicada's wing cast into PMMA. (B) Detail on foil with holes done by pillars on cicadas wing. (C) Gold foil and 100 nm holes with thickness 50 nm. (D) Detailed view with distinct gold grains. (E) The gold foil after heating on approx. 300°C. (F) Gold foil with 100 nm holes. The area with "copper colour". (G) A scheme of nanocasting of bio- template. A, B, C, D and E are SEM mi- crographs. (A) Drop of water with volume of 2 microliters on cicada wing with 5 nm thick layer of SnO . Before UV irradition (B) Water drop on the same surface as (A) after 15 minutes of UV irraditation. (C) Water drop after 30 minutes of UV irraditation. (D ) Water drop after 45 minutes of UV irraditation. (E, F,) SEM micrographs of dorsal side of cicada wing with with 5 nm layer of semi-condutive SnO . (G) Selective wetting of cicada wing with SnO layer by watter. Shape of “cross” was obtained by exposuring the wing over mask to UV radiation. (H) Scheme of photocatalyst reaction. G 2 2 + -2H 2 +H O 2 -H O DARK / O Sn Sn Sn Sn 4+ 4+ 3+ 3+ O vacancies OH OH UV H 1 μm 100 nm A B C DE F G _1 2 - O 2 2 2 2 2 2 2 4+ 4+ Sn Sn G 2 Conclusion Cicada wings appear to be a suitable natural template, that can be copied or imprinted in the polymers. Very successful way, how prepare replicas in details in tens of nanometers, is nanocasting. We have developed a relatively simple and fast way to create the film with 100 nm apertures in PMMA or PDMS. Gold foils with 100 nm apertures were prepared as promising material, which is suitable for use in SERS. For preparation of such surfaces, this procedure is very good competitor to oher methods, for example nanolithography. One possible modification of the wings of cicadas is the controlling of their hydrophobic properties. Deposi- tion of suitable materials such as semiconducting oxides (TiO , ZnO, SnO ) allowes change their surface prop- erties by UV raditation. We can transform the hydrophobic state of a surface into hydrophilic in a relatively short time of exposure. It would be possible to control the movement of liquid over the surface by defined path of the irradiation. 2 2 Biomimecs is a modern discipline, which deals with the use of natural structures to create funconal materials. Natural paerns can be modified, replicated or mimicked and materials with interesng properes can be created. Bioinspired nanostructured surfaces which are highly hydrophobic, and which can be found on leaves of water plants or insect wings, have already found technological applicaons because they are much more effecve than chemically treated flat surfaces. Surface of cicada’s wings is covered with arrays of nanopillars and reveals high hydrophobicity. Using laser ablaon, the chinous nanopillars were covered by thin layers of SnO or TiO . These chemical modificaons resulted in reversibly light- and heat-switchable surface weability. Also, the surface reliefs of wings were negavely and posively replicated by nanocasng into poly(dimethylsulfoxide) (PDMS) and into poly(methylmetacrylate) (PMMA). The PMMA replicas were spuer covered with gold or silver. The ultrathin noble metal foils appear to be promising material in research of surface-enhanced Raman scaering (SERS). 2 2 References 1) Zhang, G. et al.: Cicada wings: a stamp from nature for nanoimprinng lithography. Small 2006, 49, 1440-1443 2)Koatovski, G. et al.: Nanoimprinted opcal fibres: Biotemplated nanostructures for SERS sensing. Biosensors and Bioelectronics 24 (2009, 1531 - 1535) 3) Jari Malm et al.: Photo - ControlledWeability Switching by Conformal Coang of Nanoscale Topographics with Ultrathin Oxide Films. Chem. Mater. 2010, 22, 3349 - 3352 4)Toshiya Watanabe et al.: Photocatalyc Acvity and Photo-Induced Weability Conversion of TiO Thin Film Prepared by Sol-Gel Process on a Soda-Lime Glass. Journal of Sol-Gel Science and Tech- nology 19 , 2002, 71 – 76 2 Acknowledgement This work was supported by grants GAAV KAN401220801, Ministry of Education, Youth and Sports, project COST OC09038, and GAČR 203/09/1117.
Transcript of Cicada wings as biotemplate and their modi˜cationsiss.fzu.cz/Previous/LS2011/posters/Berger - Devet...
Cicada wings as biotemplate and their modi�cations
Jan Bergera, Jan Proškaa, Filip Novotnýa, Radek Fajgarb
(a) Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Dept. of Physical Electronics, Břehová 7, 115 19 Praha 1, Czech Republic, [email protected](b) Institute of Chemical Process Fundamentals of the ACSR, v. v. i., Rozvojová 2/135, 16502 Praha 6, Czech Republic, [email protected]
Su
Introduction Cicada (Pomponia intermedia)
A
CB
D
Cicada wing is covered with hexagonally ordered papillary. The pillars have height about 400 nm and their diameter is about 120 nm. The morphology is identical for the dorsal and ventral surfaces and be-tween male and female specimens. Structure consisting of arrays of pillars has anti-re�ection function and therefore the wings are trans-parent (in broad band from approximately 450 nm to 2500 nm).Chitinous strucuture on upper side of wing shows hydrophilic prop-erties, which are increased by epicuticular waxes. Hydrophobicity can be explained by Wenzel's model or Cassie-Bexters model. The wing is appropriate template for replication and function modi�cations. Cutitular waxes are very important during replication because enable easier separation of negative replica from template.
(A) Pomponia intermedia. (B) Large area of a dorsal side a of cicada’s wing with chitin-ous pillars. (C) Detail of array of pillars - side view. (D) Drop of water (volume of 2 micro-liters) on upper side of wing.
1 µm 200 nm
A
B C
D
Replications and nanocastingReliefs with typical dimension in the order of ten nanometers can be replicated using the method of casting (nanocasting) into suitable polymer matrice such as PMMA or PDMS. The polymer is poured on a specially prepared surface that we want to replicate. After curing, we can easily separate a negative replica in polymer from the template and manipulate with it. The polymer replica serves as the intermedi-ate template for the preparation of self-supporting gold foil with aper-tures about 100 nm - dimension interesting for applications in photon-ics and as a substrate for SERS (Surface Enhanced Raman Spectros-copy). Large (macroscopic) areas can be reproduced in the high de-tails. Short heating of the gold foil (about 300°C for 15 seconds) results in uniform reduction of nanoholes diameters.
1001001100100 nm
F
PMMA / PDMS
PMMA / PDMS
Template
Template
2 µm 100 nm
1 µm 100 nm
FE
100 nm100 nm
E
Photo-controled wettability of surfacesHydrophobic properties of the cicada wings can be further modi�ed and used for another purposes. One way how to modify this natural material is deposition of thin layer of semiconductor oxides using ArF excimer laser ab-lation of ZnO, SnO , and TiO targets, respectively. After deposition of 5 nm of SnO on the surface of cicadas wing, we have ob-tained a substrate, which was hydrophobic. However, in the presence of water (for example air humidity) and exposure to UV radiation, a chemical reaction occurs and the wing surface become super-hydrophilic.
In these inorganic oxides (ZnO, SnO , TiO ), the photogenerated formation of electron-hole pairs leading to oxygen-de�cient surface sites is believed to be responsible for the e�ect. Hydroxyl group adsorption on the defect sites is prefered to oxygen adsorption, leading to low water contact angle. The original hydrophobic state is then restored as the hydroxyl groups are re-placed by ambient oxygen during storage in dark.
Irradiation was carried out 60 minutes with UV lamp with an output 2 x 8 W at a wavelength 366 nm.
G
A B
C D
F
(A) A negative replica of cicada's wing cast into PMMA. (B) Detail on foil with holes done by pillars on cicadas wing. (C) Gold foil and 100 nm holes with thickness 50 nm. (D) Detailed view with distinct gold grains. (E) The gold foil after heating on approx. 300°C. (F) Gold foil with 100 nm holes. The area with "copper colour". (G) A scheme of nanocasting of bio-template. A, B, C, D and E are SEM mi-crographs.
(A) Drop of water with volume of 2 microliters on cicada wing with 5 nm thick layer of SnO . Before UV irradition (B) Water drop on the same surface as (A) after 15 minutes of UV irraditation. (C) Water drop after 30 minutes of UV irraditation. (D ) Water drop after 45 minutes of UV irraditation. (E, F,) SEM micrographs of dorsal side of cicada wing with with 5 nm layer of semi-condutive SnO . (G) Selective wetting of cicada wing with SnO layer by watter. Shape of “cross” was obtained by exposuring the wing over mask to UV radiation. (H) Scheme of photocatalyst reaction.
G
2
2
+-2H2+H O
2-H O DARK / OSn Sn
Sn Sn
4+ 4+
3+ 3+
O
vacancies OH OH
UV
H
1 µm 100 nm
A B C D
E F G_12- O2
2
2
2 2
2
2
4+ 4+Sn Sn
G
2
ConclusionCicada wings appear to be a suitable natural template, that can be copied or imprinted in the polymers. Very successful way, how prepare replicas in details in tens of nanometers, is nanocasting. We have developed a relatively simple and fast way to create the �lm with 100 nm apertures in PMMA or PDMS. Gold foils with 100 nm apertures were prepared as promising material, which is suitable for use in SERS. For preparation of such surfaces, this procedure is very good competitor to oher methods, for example nanolithography.
One possible modi�cation of the wings of cicadas is the controlling of their hydrophobic properties. Deposi-tion of suitable materials such as semiconducting oxides (TiO , ZnO, SnO ) allowes change their surface prop-erties by UV raditation. We can transform the hydrophobic state of a surface into hydrophilic in a relatively short time of exposure. It would be possible to control the movement of liquid over the surface by de�ned path of the irradiation.
2 2
Biomimetics is a modern discipline, which deals with the use of natural structures to create functional materials. Natural patterns can be modified, replicated or mimicked and materials with interesting properties can be created. Bioinspired nanostructured surfaces which are highly hydrophobic, and which can be found on leaves of water plants or insect wings, have already found technological applications because they are much more effective than chemically treated flat surfaces. Surface of cicada’s wings is covered with arrays of nanopillars and reveals high hydrophobicity. Using laser ablation, the chitinous nanopillars were covered by thin layers of SnO or TiO . These chemical modifications resulted in reversibly light- and heat-switchable surface wettability. Also, the surface reliefs of wings were negatively and positively replicated by nanocasting into poly(dimethylsulfoxide) (PDMS) and into poly(methylmetacrylate) (PMMA). The PMMA replicas were sputter covered with gold or silver. The ultrathin noble metal foils appear to be promising material in research of surface-enhanced Raman scattering (SERS).
2 2
References1) Zhang, G. et al.: Cicada wings: a stamp from nature for nanoimprinting lithography. Small 2006, 49, 1440-1443 2)Koatovski, G. et al.: Nanoimprinted optical fibres: Biotemplated nanostructures for SERS sensing. Biosensors and Bioelectronics 24 (2009, 1531 - 1535)3) Jari Malm et al.: Photo - ControlledWettability Switching by Conformal Coating of Nanoscale Topographics with Ultrathin Oxide Films. Chem. Mater. 2010, 22, 3349 - 33524)Toshiya Watanabe et al.: Photocatalytic Activity and Photo-Induced Wettability Conversion of TiO Thin Film Prepared by Sol-Gel Process on a Soda-Lime Glass. Journal of Sol-Gel Science and Tech-nology 19 , 2002, 71 – 76
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Acknowledgement This work was supported by grants GAAV KAN401220801, Ministry of Education, Youth and Sports, project COST OC09038, and GAČR 203/09/1117.
