Wideband Method to Enhance the Terahertz Penetration in Human Skin Based on a 3-D Printed Dielectric Rod Waveguide

In this paper, a wideband method based on a three-dimensional (3-D) printed dielectric rod waveguide (DRW) is proposed to enhance the terahertz (THz) penetration in the human skin. Two skin models are established to mimic the electromagnetic environments in the hydrated and dehydrated skin tissue, and the characteristics of the DRW are analyzed in detail. Three human tissues embedded in paraffin are measured to test the performance of the DRW. Experimental results demonstrate that the DRW generates an average penetration enhancement of 28% from 140 to 220 GHz compared with the conventional waveguide, which is rather close to the simulation prediction. Meanwhile, the DRW can significantly increase the dynamic range of the reflection signal from the skin tissue, which is meaningful in clinical application. The design of the DRW described here can be easily applied to other THz band, and the 3-D printing technique makes the fabrication flexible.