###### Abstract  
Additive manufacturing, commonly called 3D printing, has been studied extensively because it can be used to fabricate complex structures; however, polymer-based 3D printing has limitations in terms of implementing certain functionalities, so it is limited in the production of conceptual prototypes. As such, polymer-based composites and multi-material 3D printing are being studied as alternatives. In this study, a DLP 3D printer capable of printing multiple composite materials was fabricated using a movable separator and structures with various properties were fabricated by selectively printing two composite materials. After the specimen was fabricated based on the ASTM, the basic mechanical properties of the structure were compared through a 3-point bending test and a ball rebound test. Through this, it was shown that structures with various mechanical properties can be fabricated using the proposed movable-separator-based DLP process. In addition, it was shown that this process can be used to fabricate anisotropic structures, whose properties vary depending on the direction of the force applied to the structure. By fabricating multi-joint grippers with varying levels of flexibility, it was shown that the proposed process can be applied in the fabrication of soft robots as well. multi-composite materials; photo-polymerization; additive manufacturing; 3D printing; photochromic; laminar composite +
Footnote †: journal: Applied Sciences  
**Citation:** [PERSON]; [PERSON]. Property Analysis of Photo-Polymerization-Type 3D-Printed Structures Based on Multi-Composite Materials. _Appl. Sci._**2021**, \(I\), 8545. [[https://doi.org/10.3300/app11188545](https://doi.org/10.3300/app11188545)]([https://doi.org/10.3300/app11188545](https://doi.org/10.3300/app11188545))  
Academic Editor: [PERSON] Received: 30 June 2021  
Accepted: 8 September 2021  
Published: 14 September 2021  
**Problems:** MDP1 stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. **Citation:** (2021) 11 - 1  
and organs [13], although there are many restrictions on its functional implementation, meaning it is limited to the production of conceptual prototypes. Polymer-based composites and multi-material printing are being studied as new alternatives to impart various selective functionalities to 3D-printed structures [14; 15; 16; 17]. In particular, among the various 3D printing methods, research cases using the photo-catalytic reaction method, which can lower equipment costs while maintaining high resolution and good surface quality, have been published extensively [18; 19]. Among the photo-catalytic reaction methods, material jetting (MJ) is based on an inkjet structure, meaning it has advantages in terms of the printing quality and material diversity through the use of multiple nozzles [20]; however, in the MJ method, since the material is sprayed through a fine nozzle and then cured by ultraviolet light as is, if a material is used with physical properties that are difficult to control, the quality is greatly reduced [21]. In addition, if a composite material containing powder is used, abrasion and clogging of the fine nozzle may occur due to the powder; that is, since most of the composite materials used for 3D printing contain various functional powder materials, the viscosity of the resin used increases and aggregation occurs, which makes it difficult to use them in MJ 3D printing. For this reason, recently the printing of functional composite materials using photo-polymerization (PP) has been actively studied [22; 23; 24; 25]. Among these studies, a method involving the curing of resin using a DLP projector has been widely used due to the relatively low price and high printing speed involved. Figure 1 shows a schematic diagram of the photo-polymerization process based using a DLP projector when photochromic pigments are used as the functional powder materials.