Sains Malaysiana 49(7)(2020): 1491-1498

http://dx.doi.org/10.17576/jsm-2020-4907-02

Frictional Properties of the Wax Coverings in Nepenthes alata Slippery Zone: Results from AFM Scanning

(Sifat Geseran Penutup Lilin di Zon Licin Nepenthes alata: Hasil daripada Pengimbasan AFM)

LIXIN WANG*, SHUOYAN ZHANG, LINLIN ZHANG & SHANSHAN LI

School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, People’s Republic of China

Received: 8 April 2019/Accepted: 13 March 2020

ABSTRACT

Slippery zone of Nepenthes alata presents anisotropic friction behaviors depending on its evolved structures. Studies have demonstrated the contribution of lunate cells, but the role of wax coverings has not been specially investigated. In this paper, we showed findings obtained from AFM scanning and SEM observation on characterizing the frictional properties of wax coverings. Friction data generated by the AFM cantilever on wax coverings along downward and upward directions were different. The difference was insignificant (2.56%) when applying the load force of 300 nN, but increased (4.83-8.40%) when applying the load force of 500-1500 nN. The scanned wax coverings showed no detectable damage when applying the load force of 300 nN, whereas observable damage was presented when the load force exceeded 500 nN. When the load force increased to 1500 nN, the wax coverings were destroyed completely. The results suggest the wax coverings depend on their surface morphology and structural characteristic to generate different frictional properties in different directions, but the difference was inconspicuous to declare the surface anisotropy. This study is helpful for further understanding the anisotropic properties of slippery zone, and motivates the slippery zone to be a bionic prototype for designing anisotropic surfaces.

Keywords: Biotribology; frictional properties; slippery zone; surface anisotropy; wax coverings

ABSTRAK

Zon licin Nepenthes alata menunjukkan tingkah laku geseran anisotropik bergantung pada strukturnya yang berkembang. Kajian telah menunjukkan sumbangan sel-sel lunat, tetapi peranan penutup lilin belum dikaji secara khusus. Dalam makalah ini, kami menunjukkan penemuan yang diperoleh daripada pengimbasan AFM dan pemerhatian SEM mengenai ciri sifat geseran penutup lilin. Data geseran yang dihasilkan oleh julur AFM pada penutup lilin pada arah bawah dan atas adalah berbeza. Perbezaannya tidak bererti (2.56%) apabila menggunakan daya beban 300 nN, tetapi meningkat (4.83-8.40%) ketika menggunakan daya beban 500-1500 nN. Penutup lilin yang diimbas tidak menunjukkan kerosakan boleh kesan ketika menerapkan daya beban 300 nN, sedangkan kerosakan boleh kesan ditunjukkan ketika daya beban melebihi 500 nN. Apabila daya beban meningkat kepada 1500 nN, penutup lilin hancur sepenuhnya. Keputusan kajian menunjukkan penutup lilin bergantung pada morfologi permukaan dan ciri strukturnya untuk menghasilkan sifat geseran yang berlainan dalam arah yang berbeza, tetapi perbezaannya tidak jelas untuk menyatakan anisotropi permukaan. Kajian ini berguna untuk lebih memahami sifat anisotropik zon licin, dan mendorong zon licin untuk menjadi prototip bionik bagi merancang permukaan anisotropik.

Kata kunci: Anisotropi permukaan; biotribologi; penutup lilin; sifat geseran; zon licin

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*Corresponding author; email: wanglx@hebust.edu.cn