## 1 Introduction  
Livestock waste is accumulating with the expansion of the livestock breeding scale, which has resulted in serious pollution of the ecological environment. The use of insects to recycle livestock has been confirmed as a sustainable solution [1, 2]. The application of BSF to dispose of livestock waste and to achieve resource utilization has become a focal point of current research [3, 4, 5]. The BSF sand mixture (the black soldier fly larvae (BSFL) and the BSF organic fertilizer) is harvested through the bioconversion of livestock waste, in which high-protein BSFL are employed as the protein feed of aquatic animals [6]. The BSF organic fertilizer sand is rich in active substances that act against plant diseases. It exhibits a high fertility and has served as an effective alternative fertilizer source for fruits, vegetables, and herbage [7]. At present, researchers worldwide have primarily focused on the bioconversion efficiency of BSF [8, 9], the growth changes in BSF [10, 11], the application of BSF organic fertilizers [12, 13, 14], the efficacy of BSFL protein [15, 16], and BSFL that are rich in amino acids [17; 18]. Moreover, considerable research and exploration have been performed. The research results have further confirmed that the application of BSF to build a saprophytic chain is a vital measure facilitating the resource utilization of livestock waste. Two-step and three-step earthworm separators were developed to examine the optimal harvest parameters and the key kinetic mechanism so as to shorten the harvest time of vermicompost fields and reduce the separation costs [19; 20]. Compared with earthworms, the BSF and mixture includes a certain moisture content, and some material particles are bonded to each other, which exhibit complex characteristics and significant differences in composition. The conventional screening technology and equipment have a low screening efficiency and are prone to blocking, thus limiting the resource utilization of the BSF sand mixture. Researchers worldwide have focused on the separation and cleaning of waste plastic film and impurities [21], cabbage seeds [22], soybean seeds [23], corn [24], rapeseed [25], and other materials over the past few years. To be specific, pneumatic screens, vibrating screens, tremmel screeners, and other separation or sorting devices have been designed. The effects of the sieve size, type, arrangement, and operating parameters on the separation effect have been investigated, and a good screening efficiency and some theoretical research results have been achieved. Additionally, some research has considered factors (e.g., the wet agglomerating morphology change [26], blocking failure [27; 28], bionic screen [29; 30; 31], and air flow [32; 33; 34]) and explored their effects on screening. Nevertheless, the results of existing experiments have suggested that the physical properties of the respective components are complex, and the morphology is different due to the adhesion of some particles in the BSF sand mixture [35] and the soft tissue of the BSFL [36]. The mechanical-physical properties and aerodynamic properties of the sieving objects are significantly different from those of the conventional screening objects. Accordingly, the separation effect of the existing screening equipment remains poor. The BSFL are easily damaged by external forces (e.g., extrusion and impact). Moreover, the BSFL are mixed with sand, which increases the difficulties in screening, thus resulting in the increased impurity rate in the BSFL. Biological separation is not satisfactory compared with mechanical separation. The BSFL can be lured or stressed through external environmental regulation. Furthermore, BSFL are capable of actively crawling and being separated from the base material, including bait trapping [37], light separation [38], thermal separation [39], water separation [39], electric field separation [40; 41; 42], etc. However, the separation efficiency completely depends on the wriggling and crawling of BSFL.