## 1 Introduction  
With high social development and better living quality, people start to pay more attention to functional textile products more than simply comfortable textile ones, which makes the invention of functional products become a priority in the textile field. Public awareness of hygiene has increased, which in turn makes the antimicrobial concept widespread knowledge in today's society [1, 2, 3]. When wearing textile garments, people metabolize and produce sebun cutaneous, sweat, and scales. These metabolites are nonvisment for microorganisms that are the smallest creatures that cannot be observed by naked eyes. Microorganisms can be divided into bacteria, fungus, and virus, and the former can grow to a tremendous population almost everywhere. For instance, _Escherichia coli_ (_E. coli_), one type of Gram-negative bacteria, can grow over the textiles and degenerate them in termsof discoloring, causing inferior quality, generating repulsive odors, and contaminating the environment. Worse, _E. coli_ also survives in waters, soils, feces, and the human and animals' digestive systems and skins and can inflict people with diarrhea [4; 5; 6].  
Common antibacterial agents in the market involve inorganic, organic, and natural types. In the early stage, the majority of antibacterial agents are organic, because they have the optimal antibacterial performance. Nonetheless, the effect is not long lasting, and the stability is low otherwise, due to which organic antibacterial agents are gradually replaced by inorganic types [7; 8; 9]. Inorganic antibacterial agents are commonly used in disinfection, featuring long-lasting efficacy, high temperature resistance, and benefits to the environment and human health [10; 11] and have been used in plastic, ceramics, and stainless steel in recent years. A recent study showed that most antimicrobial substrates used in the manufacturing process are mercury, silver, ZrO\({}_{2}\), zinc oxide, and chlorogenic acid (CGA). Among these antimicrobial agents, mercury is poisonous and, thus, banned, but silver antibacterial materials have a higher production cost. Chlorogenic acid (CGA) could be applied as a natural product to improve the antibacterial ability, but the using condition was highly restricted, and the transformation from ZrO\({}_{2}\) crystalline forms is a serious problem in the biomedical field. As a result, zinc oxide exhibits the most potential due to its intrinsic safety and stability with eco-friendly, ultraviolet resistant, and antimicrobial attributes [12; 13]. Hence, zinc oxides have commonplace uses in sunblock, waste water, vectorial membranes of artificial teeth, and the textile field, becoming a critical material in developing green textiles [14; 15; 16; 17].  
The employment of twisting or wrapping may render functional yarns with a structural change, which may restrict the functions from effectuating. Some researchers studied the hygroscopicity of functional yarns as related to the conduction of twisting. They found that excessive twisting damaged the yarn structure and reduced the capillary effect [18; 19]. Therefore, in this study, two or three piles of zinc ion yarns are made into twisted yarns via a rotor spin device, and in the meanwhile, the rotating speed difference (between the winding and take-up rates) is changed during the twisting process. Next, a fully computerized, high-efficiency, single-cylinder hosiery machine is used to fabricate functional antibacterial knnitted fabrics, after which the mechanical properties, water vapor transmission rate, air permeability, antibacterial OD value, colony count, and antimicrobial efficacy of the knitted yarn are examined, thereby evaluating the optimal manufacturing parameters. These results are of great significance for the design of low-cost, eco-friendly, sustainable, and mass-produced products.