Human Body Effects on Inkjet-Printed Flexible Rf Interconnections

Abstract

Abstract-The effect of human body on inkjet-printed flexible singlelayer transmission lines in immediate proximity of body is investigated by simulations and measurements up to 9 GHz. A multiline extraction method is used to obtain effective material parameters allowing detailed analysis of body effects. Already at 1 mm distance from the body, the line properties converge toward the free-space values. However, at smaller distances and in direct contact with the body, often required in biosensor applications, there is a significant change in characteristic impedance and increase in losses. The results of the paper can be used to evaluate the body effects at different frequencies and at different small distances from the body.

Radio Interface Design for Inkjet-Printed Biosensor Applications

“…There is only a slight shift in operation frequency, indicating 0.3 mm to be a safe distance. This is in agreement with [15], where the body effect on high-frequency interconnections was found to be small already at 200 µm from the body.…”

“…Highfrequency analysis with multiline characterization method [18][19][20] [21] confirmed the validity of using the dc value at 2.4 GHz. The loss tangent and relative permittivity of human body are available at [22] from which they were defined for simulations as frequency dependent parameters [15]. For on-body operation, a 0.3 mm thick layer of plaster (polyacrylate, with r = 1.4 and tan δ = 0.02) was used between the body and sensor.…”

“…Following [15], the presence of body was considered in simulations using the material parameters listed in Table 1. The effect of body is illustrated in Fig.…”

“…However, the body effects on other RF structures and circuits have received little attention. The research [15] has shown, that at distances less than 0.5 mm from the body can have effect on characteristic impedances and losses of RF interconnections. According to another research [16], the operation of simple discrete RF circuits can be significantly tuned in close proximity of human body.…”

Electrical lengths and phase constants of stretchable coplanar transmission lines at GHz frequencies

“…In addition, radio frequency (RF) and microwave circuit technologies bear their own specific design challenges. Beside the common mechanical requirements like good adhesion of the metal structures to the substrate and sufficiently high structural precision on the scale of the guided wavelengths, additional effects like the frequency-dependent properties of complex-valued dielectric permittivity and electrical conductivity may give rise to increasing dispersion, losses due to dissipation [11], mode conversion, or (parasitic) radiation [12]. Variations of the electrical lengths may cause impedance mismatch or detuning of frequencyselective devices.…”