###### Abstract
The UV-curable resin used in the photo-polymerization method is basically composed of a monomer, an oligomer, a photo-polymerization initiator, an absorber, and other components. When UV light is irradiated onto the resin, the initiator in the resin absorbs the UV energy of a specific wavelength to generate radicals or cations in order to induce polymerization, thereby forming a link between materials such as the monomers and oligomers to make a polymer [26]. At this time, the photochromic powder mixed with the composite material in this study exists in a physically dispersed state in the UV-curable resin; therefore, as a chemical photo-polymerization reaction occurs due to the ultraviolet light, a link is formed between the monomer and the oligomer and the powder is physically trapped between the linked materials, thereby making causing composite material solidification reaction. When one layer is solidified in this way, the shape of the next layer is irradiated after the \(Z\)-axis stage movement and the three-dimensional solid structure is completed via repeateded additive printing. There are, however, limitations to this approach, in that it is difficult to print various materials selectively, along with the sedimentation of functional powders that occurs because printing is performed while the resin is immersed in a vat without a repetitive material supply process. Nevertheless, since the photo-polymerization method has a great advantage in terms of material diversity, various studies involving the printing of multi-composite materials are continuously being attempted. Various other methods have  
Figure 1: Photo-polymerization of resin with functional powder added. been studied, including a printing method involving a rotating vat containing different resins [27], a method involving pneumatically injection and replacement of the resin in the vat [28], a method involving supply of resins using a syringe instead of a vat [29; 30; 31], and a method involving the coating of resins on thin film [32]; however, these methods have limitations in their application because the equipment involved may be excessively large compared to the size of the printed product, the zero point of the \(Z\)-axis may be shifted due to vat changes due to material switching, or powder sedimentation problems may occur. As such, in this study, a new process and new equipment capable of printing multi-composite materials are proposed, involving a movable separator being installed in the resin vat. Since the proposed equipment does not require additional installation space, it has excellent compatibility with existing equipment, and because it is based on a single resin vat, there is no risk of shifting the origin of the \(Z\)-axis. Even when switching materials. In addition, since it is possible to generate repetitive forced flow during the 3D printing process, the problem of powder sedimentation can also be improved. Through this, the selective additive printing of multi-composite materials can be performed to evaluate various mechanical properties of the printed structure. In addition, by selective printing with appropriately rigid or flexible materials, application cases such as anisotropic structures and multi-joint grippers can be fabricated and the physical properties can be evaluated.