TY - JOUR
T1 - Microscale Mechanism of Age Dependent Wetting Properties of Prickly Pear Cacti (Opuntia)
AU - Rykaczewski, Konrad
AU - Jordan, Jacob S.
AU - Linder, Rubin
AU - Woods, Erik T.
AU - Sun, Xiaoda
AU - Kemme, Nicholas
AU - Manning, Kenneth C.
AU - Cherry, Brian
AU - Yarger, Jeffery
AU - Majure, Lucas C.
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/9/13
Y1 - 2016/9/13
N2 - Cacti thrive in xeric environments through specialized water storage and collection tactics such as a shallow, widespread root system that maximizes rainwater absorption and spines adapted for fog droplet collection. However, in many cacti, the epidermis, not the spines, dominates the exterior surface area. Yet, little attention has been dedicated to studying interactions of the cactus epidermis with water drops. Surprisingly, the epidermis of plants in the genus Opuntia, also known as prickly pear cacti, has water-repelling characteristics. In this work, we report that surface properties of cladodes of 25 taxa of Opuntia grown in an arid Sonoran climate switch from water-repelling to superwetting under water impact over the span of a single season. We show that the old cladode surfaces are not superhydrophilic, but have nearly vanishing receding contact angle. We study water drop interactions with, as well as nano/microscale topology and chemistry of, the new and old cladodes of two Opuntia species and use this information to uncover the microscopic mechanism underlying this phenomenon. We demonstrate that composition of extracted wax and its contact angle do not change significantly with time. Instead, we show that the reported age dependent wetting behavior primarily stems from pinning of the receding contact line along multilayer surface microcracks in the epicuticular wax that expose the underlying highly hydrophilic layers.
AB - Cacti thrive in xeric environments through specialized water storage and collection tactics such as a shallow, widespread root system that maximizes rainwater absorption and spines adapted for fog droplet collection. However, in many cacti, the epidermis, not the spines, dominates the exterior surface area. Yet, little attention has been dedicated to studying interactions of the cactus epidermis with water drops. Surprisingly, the epidermis of plants in the genus Opuntia, also known as prickly pear cacti, has water-repelling characteristics. In this work, we report that surface properties of cladodes of 25 taxa of Opuntia grown in an arid Sonoran climate switch from water-repelling to superwetting under water impact over the span of a single season. We show that the old cladode surfaces are not superhydrophilic, but have nearly vanishing receding contact angle. We study water drop interactions with, as well as nano/microscale topology and chemistry of, the new and old cladodes of two Opuntia species and use this information to uncover the microscopic mechanism underlying this phenomenon. We demonstrate that composition of extracted wax and its contact angle do not change significantly with time. Instead, we show that the reported age dependent wetting behavior primarily stems from pinning of the receding contact line along multilayer surface microcracks in the epicuticular wax that expose the underlying highly hydrophilic layers.
UR - http://www.scopus.com/inward/record.url?scp=84987654790&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84987654790&partnerID=8YFLogxK
U2 - 10.1021/acs.langmuir.6b02173
DO - 10.1021/acs.langmuir.6b02173
M3 - Article
C2 - 27537082
AN - SCOPUS:84987654790
SN - 0743-7463
VL - 32
SP - 9335
EP - 9341
JO - Langmuir
JF - Langmuir
IS - 36
ER -