The Obsession with Colocasia Esculenta's Complex Physical and Chemical Papillae Structure; Analysis of its Superhydrophobic and Hydrophilic Characteristics 1 2 2 Mrinaleni Das , Caitlin Ackerly , Tarkan Kurtoglu Newfield High School1 Introduction: Data: IR Spectroscopy - Mar 2020 ● The Lotus-effect has generated an increased interest due to its surface characteristics of Hydrophilic superhydrophobicity and self-cleaning properties (Barthlott, Mail, Bhushan, & Koch, 2017). Superhydrophobic ● Another plant that is often mentioned with the Nelumbo nucifera (lotus plant) as being highly Top of Fig 7 Fig 8 superhydrophobic is the Colocasia esculenta (elephant ear). Colocasia esculenta

● On a hydrophobic surface, water remains as a globular droplet and Superhydrophobic Leaf has a contact angle more than 150 degrees (Fig 2). Colocasia esculenta has a contact angle of 164 degrees and tilt angle of 6 degrees (Barthlott, 2016).

● The epicuticular waxes and the many different heights of papillae Contact Angle helps suspend the water droplets from the plant itself which adds to its superhydrophobicity (Barthlott et al, 2016). Fig 2 IR DATA Analysis & Discussion

Fig 1 This Iridescent Shine is the Light Shining off the Papillae - IR Scan comparing the top of the leaf to the bottom of the leaf. Fig 6. is Fig. 1 Extremely superhydrophobic leaf surfaces of (a) Colocasia esculenta, superimposed onto Fig 7. (Contact angle 164°) Euphorbia myrsinites (Contact angle 162°), and Lotus Nelumbo nucifera (Contact angle 162°), data from [7]. Leaves of all three species Fig 3 are characterized by convex (a, b) to papillose (c) cells, covered by - The peaks of the three-dimensional wax crystals(Ensikat et al. Figure 22 [Photograph]). upperside of the ● The Colocasia esculenta is covered in wax crystals, papillae, wax clusters and wax platelets leaf appear to minimizing the contact of water touching the leaf (Cheng, 2006). match the peaks ● The epicuticular waxes found on the Colocasia leaf are very thin making them susceptible to of the underside damage from being brushed against, insect damage, and fungus (Ensikat et al, 2000). ➢ The epicuticular waxes of the upperside and the underside of the leaf appear to have the same IR ● When the leaf surface becomes damaged the spacing between papillae starts to increase spectroscopy making the surface smoother and less superhydrophobic and more hydrophilic. Superhydrophobic vs Hydrophilic Superimposed Research Question: (Superhydrophobic described in yellow -lower line - Superhydrophobic IR The infrared Microscope (IR) and other beamlines will be used to compare the epicuticular Scan (top of leaf - Fig 7.) waxes of the Colocasia esculenta. A goal of the research is to determine if the leaf's is superimposed on the epicuticular wax changes from superhydrophobic to the hydrophilic condition. hydrophilic IR Scan (Fig Methods: 8. top of leaf)

SEM Images ● The peaks of the ● Superhydrophobic and Hydrophilic leaves were cut, and an ultra-thin superhydrophobic coating of gold was applied to their surfaces to increase their match the peaks of the conductivity. hydrophilic Elemental analysis ● SRX and TES Beamlines were used ➢ ***The superhydrophobic and hydrophilic IR Scans that are superimposed appear to indicate that ● Superhydrophobic (S & S ) and hydrophilic leaves (H & H ) 1 2 1 2 there is no major difference between the respective chemical composition.*** were cut in strips (approximately .5 cm by 2cm) and placed on top of kapton tape. Untreated lotus leaf Infrared Spectroscopy ● IR was used to determine the wax composition of the leaf Annealed lotus leaf ● IR light has trouble going through thick samples so a Untreated carnauba dremel was used to scrape the leaves and thin out wax the leaves. Low velocity was used to abrade the leaf Annealed carnauba until it was approximately see through. wax ● To scan the top of the leaves (both Superhydrophobic Cellulose and hydrophilic) the bottom of the leaf was abraded, and similarly, if the bottom of the leaf was ● Researchers investigated the wax composition of the lotus leaf which has similar properties as the scanned then the top was abraded. See images above of the abraded leaves. Colocasia esculenta. ● A glycerin solution of 1 part glycerin and 2 parts water was applied to the abraded section of ● SpectraBase was used to analyze the IR Spectra. the leaf to reduce desiccation before scanning. ● The main component of the wax in Colocasia esculenta is C28-1-ol (1-Octacosanol - Peak 2920 cm-1) which has a molecular formula of C28-H58-O whereas the lotus leaf is C29-H60-O (Ensikat et al, Data: SEM Images (2016 SB) Left Superhydrophobic & Right Hydrophilic 2011). ● 1-Octacosanol is a primary fatty alcohol found in epicuticular waxes Superhydrophobic SEM Hydrophilic SEM showing showing the robustness of the the flatness of the Discussion: superhydrophobic surfaces at epicuticular wax allowing for 30.00 K X Mag. EHT = 5.00 kV an increased wettability. ➢ When superimposed, the epicuticular waxes of the upperside and the underside of the leaf appear to 10.00 K X Mag, EHT = 5.00KV have the same IR spectroscopy, indicating that both are composed of 1-Octacosanol. This explains the high degree of superhydrophobicity found on both of the two leaf surfaces. The nanostructure of the The epicuticular wax surface epicuticular wax surface is smooth and damaged so ➢ There is no apparent difference between the epicuticular waxes of the superhydrophobic and repels the water due to a there is an increased contact hydrophilic surfaces. The nanostructure of epicuticular wax appears to provide undamaged leaves reduced contact angle of angle of water to leaf at 30.00 water to leaf at 30.00 K X K X Mag. EHT = 5.00 kV with a high degree of superhydrophobicity. Mag. EHT = 2.5 kV Future Studies Stomata on surface of leaf The epicuticular wax on the ● The plant material might interfere with data collection, so we are going to try removing the wax using at 10.00 K X Mag. EHT = papillae is damaged. 10.00 5.00KV K X Mag, EHT = 5.00KV various wax extraction methods from the Colocasia esculenta leaf. ● Redo the SEM images so they're similar to the format used in theIR studies . ● Compare the epicuticular wax of the Colocasia esculenta to the wax of Alocasia macrorrhiza. Data: IR Spectroscopy - Mar 2020 References: Avrămescu, R.-E., Ghica, M., Dinu-Pîrvu, C., Prisada, R., & Popa, L. (2018). Superhydrophobic Natural and Artificial Surfaces—A Structural Approach. Materials, 11(5), 866. https://doi.org/10.3390/ma11050866 Superhydrophobic Hydrophilic Barati Darband, G., Aliofkhazraei, M., Khorsand, S., Sokhanvar, S., & Kaboli, A. (2020). Science and Engineering of Superhydrophobic Surfaces: Review of Corrosion Resistance, Chemical and Mechanical Stability. Arabian Journal of Chemistry, 13(1), 1763-1802. https://doi.org/10.1016/j.arabjc.2018.01.013 Barthlott, W., Mail, M., Bhushan, B., & Koch, K. (2017). 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Superhydrophobic Polystyrene by Direct Copy of a Lotus Leaf. BioNanoScience, 1(4), 136-143. https://doi.org/10.1007/s12668-011-0017-2 Nasri, N. S., Ahmed, M. M., Mohd Noor, N., Mohammed, J., Hamza, U. D., & Mohd Zain, H. (2014). Hydrophobicity characterization of bio-wax derived from taro leaf for surface coating applications. Advanced Materials Research, 1043, 184-188. https://doi.org/10.4028/www.scientific.net/AMR.1043.184 Qu, M., He, J., & Zhang, J. (2010). Superhydrophobicity, Learn from the Lotus Leaf. Biomimetics Learning From Nature. https://doi.org/10.5772/8789 Ravindran, V., Sivakanesan, R., & Cyril, H.W. (1996). Nutritive value of raw and processed colocasia (Colocasia esculenta) corm meal for poultry. Animal Feed Science and Technology, 57(4), 335-345. https://doi.org/10.1016/0377-8401(95)00861-6 Samaha, M. A., Tafreshi, H. V., & Gad-el-Hak, M. (2012). Superhydrophobic surfaces: From the lotus leaf to the submarine. Comptes Rendus Mécanique, 340(1-2), 18-34. https://doi.org/10.1016/j.crme.2011.11.002 Bottom of Yamamoto, M., Nishikawa, N., Mayama, H., Nonomura, Y., Yokojima, S., Nakamura, S., & Uchida, K. (2015). Theoretical Explanation of the Lotus Effect: Superhydrophobic Property Changes by Removal of Nanostructures from the Surface of a Lotus Leaf. Langmuir, 31(26), 7355-7363. https://doi.org/10.1021/acs.langmuir.5b00670 Colocasia Yang, H., Liang, F., Chen, Y., Wang, Q., Qu, X., & Yang, Z. (2015). Lotus leaf inspired robust superhydrophobic coating from strawberry-like Janus particles. NPG Asia Materials, 7(4), e176. https://doi.org/10.1038/am.2015.33 esculenta Leaf Fig 9A. Fig 6 TopTop Alocasia macrorrhiza Acknowledgements (Also called elephant Fig 8 ear- leaves point We would like to acknowledge the support of the NSLS-II staff, specifically of beamlines IR-Infrared Imaging and upwards) Microspectroscopy especially Lisa Miller, Ashwin Ambi and Tiffany Victor for help with data collection and analysis. We

BottomFig 9B. would also like to acknowledge the NSLS-II User Office, L. Miller, G. Cisco, G. McKenzie and the Office of Educational Bottom Alocasia macrorrhiza Programs, K. White and S. Bronson for support of the SPARK program. This research utilized beam lines IR-Infrared - Future Research Imaging and Microspectroscopy of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Finally, thank you to all members of the SPARK Spectroscopy Collaboration.