Biomimicking the Salvinia effect with carbon nanotubes

Gas adsorption₂

Vertically aligned CNTs are ideal model structures to understand gas adsorption (CO₂, N₂, SO₂, NO₂, H₂) in carbon nanomaterials. Why is this the case? VACNTs are chemically robust mesoporous materials with moderately high surface area (ca. 600 cm₂/g). They present ideally 1D ordered sp₂ carbon systems which allow to understand their adsorption characteristics theoretically. Various surface anchoring groups can be introduced by gas phase functionalization processes keeping their microscopic alignment and arrangement intact. Using elastocapillary effects microscopic sized pores can be introduced which change their adsorption behavior.

Dry adhesion

In the animal kingdom dry adhesion is a widely observed effect and responsible for the movement of smaller insects like spiders and flies even up to larger size animals like geckos or lizards. They use a multitude of single fibrilliar structures on their extremities called setae to adhere to a variety of different structured surfaces. VACNTs are ideally suited artificial materials to mimick such biosurfaces. They are mechanically and chemically robust, high flexible and can be chemically modified to adjust their adhering properties individually. I some instances they outperform their natural counterparts. Their potential for technological is enormous.

Water adsorption for gas keeping and exchange, slip and drag reduction

The surface of VACNTs is hydrophobic in its virgin state (contact angle < 90°). However, their surface can be chemically modified in both directions, resulting in hydrophilic as well as superhydrophobic surfaces which is fundamentally important for any interaction with a compound coming in close contact. To control that interaction, surface chemistry is used to alter the molecularly determined hydrophobic and hydrophilic properties of the VACNT surface. Currently reported air retention capabilities of artificial materials are limited to very few examples, often with micrometer sized structures and to the best of our knowledge the effect of under-water air retention has not been reported for carbon-based nanomaterials so far. The phenomena is called the Salvinia effect and mimics the air keeping behaviour of the natural plant salvinia molesta.

See our contributions:

• D.J. Babu, D. Puthusseri, F. G. Kühl, S. Okeil, M. Bruns, M. Hampe, J.J. Schneider “SO₂ adsorption on carbon nanomaterials: A comparative study”, Beilstein J. Nanotech., (2018), 9, 1782–1792
• D.J. Babu, M. Mail, W. Barthlott, J.J. Schneider “Superhydrophobic vertically aligned carbon nanotubes for biomimetic air retention under water (Salvinia effect)”, Adv. Mater. Interf. , (2017), 4, 1700273
• D.J. Babu, J.J. Schneider “Gas Adsorption Studies of CO₂ in Carbon Nanomaterials: A Case Study of Vertically Aligned Carbon Nanotubes”, Chemie Ingenieur Technik , (2017), 89, 1273-1287
• D. Puthusseri, D. J. Babu, S. Okeil, J. J. Schneider “Tuning gas adsorption capacity in an all carbon nanomaterial composed of carbon nanohorns and vertically aligned carbon nanotubes”, Phys.Chem.Chem.Phys., (2017), 19, 26265-26271
• D.J. Babu, M. Bruns, J.J. Schneider “Unprecedented CO₂ uptake in vertically aligned carbon nanotubes”, Carbon, (2017), 125, 327-335
• J. Patzsch, D. J. Babu, J. J. Schneider “Hierachically structured porous carbon tubes for high pressure carbon dioxide adsorption”, Beilstein J. Nanotechnology, (2017), 8, 1135-1145
• D. J. Babu, M. Bruns, R. Schneider, S. Gerthsen, J. J. Schneider “Understanding the influence of N-doping on the CO₂ adsorption characteristics of vertically aligned carbon nanotubes”, J. Chem. Phys. C , (2017), 121, 6161-626
• D. J. Babu, T. Herdt, M. Bruns, R. Staudt, J. J. Schneider “Carbon nanohorns as high performance gas and energy storage materials”, J. Mater. Chem. A, (2016), 4, 14267-14275
• D. J. Babu, F. G. Kühl, S. Yadav, D. Markert, M. Bruns, M. J. Hampe, J. J. Schneider “Adsorption of pure SO₂ on nanoscaled graphene oxide”, RSC Advances, (2016), 6, 36834-36839
• M. Rahimi, J.K. Singh, D.J. Babu, Y.-B. Yang, J.J. Schneider, F. Müller-Plathe “Double-walled Carbon Nanotube Array for CO₂ and SO₂ adsorption”, J. Chem. Phys. , (2015), 143, 124701
• D. J. Babu, S.Yadav, T. Heinlein, G. Cherkashinin, J. J. Schneider “Selective functionalization of vertically aligned carbon nanotube arrays using CO₂ plasma”, J. Phys. Chem. C. , (2014), 118, 12028-12034
• D. J. Babu, S. N. Varanakkottu, A. Eifert, D. DeKoning, G. Cherkashinin, S. Hardt, J J. Schneider “Inscribing wettability gradients onto superhydrophobic CNT surfaces”, Adv. Mater. Interf. , (2014), 1, 1300049
• M. Rahimi, J. K. Singh, D. J. Babu, J. J. Schneider, F. Müller-Plathe “Understanding carbon dioxide adsorption in carbon nanotube arrays: Molecular simulation and adsorption measurements”, J. Phys. Chem. C , (2013), 117, 13492–13501
• D. Babu, M. Lange, G. Cherkashinin, A. Issanin, R. Staudt, J. J. Schneider “Gas adsorption studies of CO₂, SO₂ and N₂ in spatially aligned double walled carbon nanotube arrays”, Carbon , (2013), 61, 616-623