致灾农业昆虫捕集滑板表面结构仿生构建与性能验证

Surface structure biomimetic design and performance testing of slippery trapping plate used for controlling agricultural insect

致灾农业昆虫光电诱导滑移捕集技术中,致使昆虫产生良好滑移行为的捕集滑板是获取该技术高效应用的关键。红瓶猪笼草(Nepenthes alata)叶笼滑移区依靠特殊形貌对昆虫附着系统表现出显著滑移功能,为致灾农业昆虫捕集滑板的研制提供了仿生原型。采用扫描电子显微镜(scanning electron microscope,SEM)与三维白光形貌干涉仪(scanning white light interferometer,SWLI)对滑移区表面微形貌进行观测分析并获取三维结构参数,据此构建了致灾农业昆虫捕集滑板表面结构的仿生模型;采用激光微纳加工技术和高压静电吸附技术实现捕集滑板的仿生制备。为验证仿生制备致灾农业昆虫捕集滑板功效,测试了蝗虫(Locusta migratoria manilensis)在捕集滑板和仿生原型的附着力,结果分别为(402.9±26.1)m N和(361.9±25.5)m N,相近的附着力预示研制的致灾农业昆虫捕集滑板具有与仿生原型类似的性能。

The technology of photoelectric inducing-trapping can kill agricultural insect（locust, ant, etc.） and protect the agricultural production from being destroyed effectively, and avoid the environment pollution caused by spraying pesticide. The key factor of this technology is to develop a kind of slippery trapping plate which can restrict insects＇ excellent attachment ability generated by rigid claw and adhesive pad. To obtain structural information for biomimetic developing the slippery trapping plate, surface morphology of bionic prototype（slippery zone of Nepenthes alata pitcher） was detailedly examined in August and September of 2013. Several sections（1 cm2） were cut from the slippery surface and rinsed in distilled water before being air-dried, then mounted on aluminum blocks and sputter coated, and observed with a scanning electron microscope（SEM）. Fresh sample（2 cm2） was cut from slippery surface and glued to an aluminum block, and examined with a scanning white-light interferometer（SWLI）. The structural parameters of slippery surface were statistically acquired via analyzing the saved images with the software belonging to the SEM and SWLI equipment. The results showed that the slippery surface is covered by a layer of dense and irregular wax crystals, along with numerous downward-directed lunate cells. Length and thickness of the platelet-shaped wax crystals was 1 109.6±68.5 nm and 89.11±5.17 nm, respectively; the height and interval distance of the lunate cells was 20.41± 1.73 μm and 71.53±3.86 μm, respectively; the angles of the lunate cell＇s slope and precipice was 23.1±2.4° and 76.1±4.0°, respectively. These obtained parameters suggested that the slippery zone bears micro-nano scaled surface architectures. Based on acquired structural parameters, biomimetic model of the slippery trapping plate was designed with CAXA software. The biomimetic model consisted of a substrate and an epicuticular layer, the substrate was covered by micro-scaled triangular prisms（simplified lunate cells） and numerous blind holes, and the epicuticular layer was composed of massive flaky graphite（simplified wax coverings） possessing the physical properties of lubrication and slippage. To prepare the slippery trapping plate, laser micro-fabrication technology was adopted to machine the micro-scaled architectures（triangular prisms and blind holes） of the substrate（alloy steel, 100 mm×50 mm×5 mm, length×width×thickness）, and high voltage electrostatic incorporation technology was used to attach the flaky graphite（mesh number 1 500-2 000, dimension 6.5-10 μm） to the machined substrate. The flaky graphite was put on an organic glass box（95 mm×45 mm×30 mm, length×width×height）; and put the laser-machined substrate and an alloy plate on the top and bottom of the box, respectively. The positive and negative electrode of high voltage electrostatic source was respectively connected to the substrate and alloy plate, and applied high voltage electrostatic（16.0-18.0 KV） for 100-120 s. With the incorporation of the high voltage electrostatic, the flaky graphite was absorbed to the blind holes of substrate and attached tightly. To test the function of the biomimetic slippery trapping plate, attachment forces of adult locust（Locusta migratoria manilensis） were measured with an insect micro-force measurement system in July 2015. The system mainly consisted of a force transducer（1-PW4C3）, a signal conditioning module（SCXI-1520）, a data acquisition platform（PCI-6221）, and data-processing displaying software. The locust was connected to the force transducer（along load direction） using a thin thread（12 cm long） fastened its neck position, and then put on the tested surface. The locust climbed on the tested surface along the load direction of the force transducer. When the thin thread started to pull, the locust crawled ahead frantically to attempt to break away from this restriction, so generated attachment forces and their maximal values were recorded. The results showed that values of attachment force provided by locust on bionic slippery trapping plate ranged from 328.7 mN to 458.3 mN, whereas on slippery surface ranged from 307.3 mN to 397.1 mN. Attachment force of locust on bionic slippery trapping plate（402.9±26.1 mN） was barely 1.1 times than that on slippery surface（361.9±25.5 mN）, suggesting the biomimetic slippery trapping plate bore rather similar function as the slippery surface, thereby achieved the protected biomimetic results. The obtained conclusion provides theoretical and technical references to biomimetic development of slippery trapping plate used for controlling agricultural insect.