The fractures was designed using the freely available OpenSCAD software (https://openscad.org/). The fracture section consisted of nine intersecting disc-shaped fractures with diameters and apertures. The fractures overlapped to form a flow-channel from one end of the model to the other end. The zigzagging structure was chosen considering the model size constraints set by the 3D printer and the need to ensure enough flow-channel surface area to obtain effective temperature data. In this study, we used an ultraviolet curing type 3D printer (Agilista 3100, KEYENCE co.) to generate a 3D-printed sample consisting of acrylic ultraviolet-curing resin. The flow-channel or cavity space was sculpted by the printer with a support material. After 3D printing the sample object, the water-soluble support material was removed to create a clean fracture structure by washing the 3D-printed sample in an ultrasonic bath for several days.
