Among 3D printing techniques, fused deposition modeling (FDM) is known for its design flexibility, rapid fabrication, and the ability to produce complex geometries without molds. However, weak interlayer adhesion often results in poor mechanical strength along the build (Z) direction, limiting its use in structural applications. Instead of altering printing parameters or switching technologies, we propose a simple microwave-irradiation post-treatment to enhance interlayer bonding in FDM-printed parts. By optimizing microwave power and exposure time, we significantly improved interlayer fusion while maintaining the original geometry. Cross-sectional microscopy before and after treatment confirmed markedly improved interlayer bonding (Unbonded interfacial area fraction: 56.82% → 15.51%; -41.31 percentage points, -72.7%). Correspondingly, the Z-direction tensile strength increased from 42.38 to 49.11 MPa (+6.73 MPa, +15.9%). This straightforward post-processing method effectively addresses a key limitation of FDM, thereby expanding its potential for structural and industrial applications.

In the heating and drying system using microwaves, an optimal design method was presented to effectively shield microwaves leakage between the door and the cylindrical applicator. In order to protect the human body from leaking microwaves, it is necessary to keep the intensity of microwaves below 5 mW/cm². The door part adopts a choke structure and includes a number of design factors, such as, fin shape, slit shape, and a gap between the applicator and the door. The geometry was optimized by design of experiments, applying full factorial design and response surface method in a 4-factor, 2-level design. The results obtained by ANSYS HFSS analysis were applied to the intensity of microwave leakage according to the change of the design factors. The shape of the choke structure was optimized using Minitab, a statistical program. The microwave heating and drying system was manufactured based on optimal design value and the leakage of microwaves between the door and the applicator was measured. We confirmed that the experimental values were consistent with the simulation values.

This study aimed to investigate the effects of static stretching of the calf muscle on ankle position sense and dynamic balance ability following microwave diathermy. Participants were 28 healthy young students in their 20 s, who were divided into a microwave diathermy stretching group (MSG) and a stretching group (SG). A microwave was emitted to the calf muscle area to participants in the MSG. Static stretching was performed by standing on a quadriceps board for 15 minutes. The angle of the wedge was set to a range of 15–25°, representing a level of pain and discomfort allowed by the subjects. Before and after intervention, ankle dorsi-plantar flexion joint position sense (JPS) and dynamic balance ability were measured. The group source affected JPS error of dorsi-plantar flexion (p < 0.05) and JPS error increased with the SG more than the MSG. There was an increase in the dynamic balance score in both groups after the intervention compared to before the intervention. Microwave therapy prior to stretching can preserve JPS and balance ability, thereby reducing the risk of injuries from activities after stretching.