{"id":1242,"date":"2021-04-07T12:47:00","date_gmt":"2021-04-07T16:47:00","guid":{"rendered":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/?p=1242"},"modified":"2023-01-13T23:16:34","modified_gmt":"2023-01-14T03:16:34","slug":"sticks-and-stones-may-break-my-bones-but-dirt-will-wash-right-off","status":"publish","type":"post","link":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/2021\/04\/07\/sticks-and-stones-may-break-my-bones-but-dirt-will-wash-right-off\/","title":{"rendered":"Sticks and stones may break my bones but dirt will wash right off"},"content":{"rendered":"\n

There you are, sitting in the park eating your spaghetti picnic on your favorite picnic blanket when your pollen allergy acts up. You let out a sneeze powerful enough to compete with Aeolus\u2019 bag of wind, but now your spaghetti is all over your favorite picnic blanket. You immediately go to rinse it off, but your fine Italian sauce has thoroughly soaked in. If only nature had a solution to keep a surface clean. Enter: the lotus leaf<\/a>.<\/p>\n\n\n\n\n\n\n\n

The lotus leaf is renowned for its ability to stay clean in murky environments. This characteristic of the plant is regularly attributed to its superhydrophobic surface features and chemistry. A superhydrophobic surface is a surface which can maintain a contact angle<\/a> with water above 150o<\/sup> and is correlated with a low free surface energy\u2014which really means water pools and rolls off rather than soaking into the surface.<\/p>\n\n\n\n

\"Nearly<\/a><\/figure>
\n

Modified from Zorba et al. 2008<\/mark><\/p>\n<\/div><\/div>\n\n\n

A key attribute of the superhydrophobic surface is a hierarchical micro- and nanostructure<\/a>. The microstructure is composed of plant cells grown in little mounds known as a \u201cpapillae\u201d with small channels for air flow in between called \u201cstomata.\u201d The nanostructure is composed of hair-like wax crystal towers (epicuticular wax) built on the peaks of the papillae topography. The elevated wax towers combined with the stomata trap air and reduce the contact area of the water with the surface. The epicuticular wax chemistry reduces the adhesion to the towers themselves by being naturally hydrophobic.<\/span><\/p>\n\n\n

\n

Modified from Zorba et al. 2008<\/mark><\/p>\n<\/div>

\"Graphic<\/a><\/figure><\/div>\n\n\n\n

The tips of the wax towers create the largest repelling forces which form larger contact angles, while shorter towers can actually produce adhesive forces that reduce the contact angle. If the air is displaced and filled with water, the contact angle will decrease due to the water-water adhesion which \u201cpulls\u201d the droplet to the surface. Similarly, if the surface is damaged, the wax can be removed and decrease the surface\u2019s hydrophobicity. The wax is naturally soft material and prone to mechanical damage increasing water adhesion and reducing the self-cleaning abilities of the leaf.<\/p>\n\n\n\n

The papillae topography is the key to the robustness of the lotus leaf hydrophobicity. The papillae create natural valleys and creases which\u2014like the tops\u2014are still densely packed with wax hairs. When the surface is impacted, only the top of the papillae are exposed to the mechanical force so the wax tubules in the valleys are left undeformed and maintain their hydrophobic characteristics.<\/p>\n\n\n\n

\"Water<\/a><\/figure>
\n

Photo by Chase Pellerin via Gear Patrol<\/mark><\/p>\n<\/div><\/div>\n\n\n\n

Hydrophobic surfaces have many applications<\/a> in everyday life, for example rain jackets and umbrellas perform their best when they are hydrophobic. Manufacturing processes rely on hydrophobic surfaces to reduce oxidation and stay clean in past-paced environments, and your favorite picnic blanket would be much less prone to spaghetti stains if it were hydrophobic. Nature has solutions to keeping surfaces clean; we just have to recognize them.<\/p>\n\n\n\n

Featured image<\/a> by Anna Sushok<\/a> under Unsplash License<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

There you are, sitting in the park eating your spaghetti picnic on your favorite picnic blanket when your pollen allergy acts up. You let out a sneeze powerful enough to compete with Aeolus\u2019 bag of wind, but now your spaghetti is all over your favorite picnic blanket. You immediately go to rinse it off, but […]<\/p>\n","protected":false},"author":3965,"featured_media":3386,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[505480,505447],"tags":[380449,81386,280588,12689],"class_list":["post-1242","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-2021-spring","category-text","tag-bio-inspired-design","tag-material-science","tag-plants","tag-technology"],"_links":{"self":[{"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/posts\/1242","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/users\/3965"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/comments?post=1242"}],"version-history":[{"count":11,"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/posts\/1242\/revisions"}],"predecessor-version":[{"id":3387,"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/posts\/1242\/revisions\/3387"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/media\/3386"}],"wp:attachment":[{"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/media?parent=1242"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/categories?post=1242"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sites.nd.edu\/biomechanics-in-the-wild\/wp-json\/wp\/v2\/tags?post=1242"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}