Gorb Elena V, Purtov Julia, Gorb Stanislav N
Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 9, 24098 Kiel, Germany.
Sci Rep. 2014 Jun 3;4:5154. doi: 10.1038/srep05154.
The wax coverage of the waxy zone in Nepenthes alata pitchers consists of two clearly distinguishable layers, designated the upper and lower wax layers. Since these layers were reported to reduce insect attachment, they were considered to have anti-adhesive properties. However, no reliable adhesion tests have been performed with these wax layers. In this study, pull-off force measurements were carried out on both wax layers of the N. alata pitcher and on two reference polymer surfaces using deformable polydimethylsiloxane half-spheres as probes. To explain the results obtained, roughness measurements were performed on test surfaces. Micro-morphology of both surface samples and probes tested was examined before and after experiments. Pull-off forces measured on the upper wax layer were the lowest among surfaces tested. Here, contamination of probes by wax crystals detached from the pitcher surface was found. This suggests that low insect attachment on the upper wax layer is caused primarily by the breaking off of wax crystals from the upper wax layer, which acts as a separation layer between the insect pad and the pitcher surface. High adhesion forces obtained on the lower wax layer are explained by the high deformability of probes and the particular roughness of the substrate.
猪笼草笼状捕虫器蜡质区的蜡覆盖层由两个明显不同的层组成，分别称为上蜡层和下蜡层。由于据报道这些层可减少昆虫附着，因此被认为具有抗粘附特性。然而，尚未对这些蜡层进行可靠的粘附测试。在本研究中，使用可变形的聚二甲基硅氧烷半球作为探针，对猪笼草笼状捕虫器的两个蜡层以及两个参考聚合物表面进行了拉脱力测量。为了解释所得结果，对测试表面进行了粗糙度测量。在实验前后检查了测试的表面样品和探针的微观形态。在上蜡层上测得的拉脱力是所有测试表面中最低的。在此，发现探针被从笼状捕虫器表面脱落的蜡晶体污染。这表明上蜡层上昆虫附着较少主要是由于蜡晶体从上蜡层脱落，上蜡层起到了昆虫脚垫与笼状捕虫器表面之间的分离层作用。在下蜡层上获得的高粘附力可通过探针的高可变形性和基底的特殊粗糙度来解释。
