Dielectric Losses of Paper in the THz Domain: Literature Review, Needs for Future Research, and Prospective Solutions

Abstract

High frequency paper‐based electronics is developing fast, with smart yet low cost applications in view. However, the dielectric losses of paper remain a difficult hurdle to overcome. First, the literature on the topic is reviewed and the contributions from moisture, air, mineral filler, and wood constituents to dielectric losses are highlighted. Then, the guidelines for future research are defined, including the need for systematic comparisons in controlled moisture conditions. In an effort to produce low loss materials for paper‐based electronics, it is proposed here to impregnate paper with a low loss substance, after removing residual water.

Implementation of a second‐order frequency selective surface filter at mmWave using paper and silver ink

“…As the dielectric parameters for the paper can vary due to the humidity, the different mineral filler agents used in the paper manufacturing, the cellulose amount and the orientation of the cellulose strands [29, 30], the paper used for the FSS substrate was measured for the THz band using the Terahertz Time‐Domain Spectroscopy (THz‐TDS) method and the results are shown in Figure 1. At 100 GHz the dielectric constant ($$\varepsilon _r$$) was ∼2.74 and the loss ($$\tan \delta$$) ∼0.28.…”

Industrial Applications of Terahertz Sensing: State of Play

“…Aiming at a more compact system, a THz fiber Bragg grating was used to measure paper thickness in [194]. The area was partially reviewed in [195]. Monitoring the ageing of oil-paper insulation in transformers was investigated in [196].…”

Quantitative Measurements of DP in Cellulose Paper Based on Terahertz Spectroscopy

“…The service life of oil-immersed power transformers is typically determined by the condition of the oil-paper insulating [ 1 , 2 , 3 ], and the degree of polymerization (DP) of the insulating paper is the most direct and reliable indicator of the oil-paper insulation condition [ 4 ]. Currently, the DP value is measured mainly regarding the viscosity method outlined in IEC 60450 [ 5 ], which is vulnerable to test procedures and destructive to the samples [ 6 , 7 ].…”

“…Insulating paper is composed of around 90% cellulose, and 6–7% lignin, and the remainder is hemicellulose (a polymer of pentose and hexose) [ 38 , 39 ]. It is generally accepted that lignin causes higher absorption than cellulose [ 1 ], and that lignin will influence the degradation of cellulose [ 40 , 41 , 42 , 43 ]. Due to its low thermal stability [ 44 ], hemicellulose may be degraded at the hotspots of insulation in the transformer.…”