Experimental and Computational Studies on the Basic Transmission Properties of Electromagnetic Waves in Softmaterial Waveguides

Abstract

Conventional waveguides are usually made of metallic materials, and they are effective pathways for the transmission of electromagnetic waves. A “Softmaterial waveguide”, by contrast, is supposed to be made of dielectric material and ionic fluids. In this work, by means of both experiment and computational simulation we examined one kind of softmaterial waveguide, which has the configuration of ionic fluids filled in and out of a dielectric tube. We investigated configurations with varied parameters, i.e., tube thickness from 0.2 mm to 5.0 mm, tube length of 2.0–12.0 cm, ionic concentration covering 4 orders of magnitude from 0.0002–2.0 mol/L, frequency of 10 Hz to 100 MHz for sine wave excitations, pulse duration of 5 ns to 100 ms for excitation pulses. We also mimicked the myelin sheath structure in myelinated axons in simulation. Both experimental and simulation results consistently showed a clear confinement effect for the energy flux of transmitting electromagnetic waves inside the dielectric tube, strongly supporting the model of softmaterail waveguide. The results revealed that the softmaterial waveguide had a low-pass nature, where the intensity of transmitted signals saturated at a duration of 10–100 μs for pulses, or cut off at frequency of 10–100 kHz for sine waves. And, the transmission efficiency increased with the thickness of the dielectric layer, as well as ion concentration of the solution. The results may help for a better understanding various electrical communication behaviors observed in biosystems, where a natural lipid membrane with bilateral fluids was suggested as the efficient pathway for pulsed neural impulses in a way similar to soliton-like electromagnetic pulses transmitting in a softmaterial waveguide.

Photons detected in the active nerve by photographic technique

“…In relation to this, further considerations can be made. The model of electromagnetic radiation coming from the node we recently proposed 19 and that one concerning the optical transmission through a myelin waveguide, previously described by Kumar and other authors [13][14][15][16]19 , are consistent with each other and with our experimental results and can be considered as a more comprehensive model, describing the whole sequence of generation and transmission of photons, in the node and through the myelin respectively. However, hypotheses describing how photons act when they reach the next node are still missing and deserve further research 13,19 .…”

“…Liu et al reported myelin sheath as a way for dramatic speed enhancement of signal propagation in nerves in the THz-infrared range 15 . Jingjing Xu et al mimicked the myelin sheath structure in myelinated axons 16 . They showed a clear confinement effect for the energy flux of transmitting electromagnetic waves inside a dielectric tube, strongly supporting the model of soft material waveguide.…”

On the delay in propagation of action potentials

“…This results in an attenuated field strength when the pulsed signal arrives at the next signal source (20,17,19,21). This model explains well the highly overlapped successive action potentials as shown in Figure 1.…”

“…The distance between two neighboring signal sources, i.e., Ranvier nodes, is as long as several millimeters, thus much longer than the Debye length (about several nanometers) of ions in an electrolyte solution resulting from screen effect (16). The electromagnetic soliton-like model states that the neural signals are electromagnetic pulses generated by the transmembrane transient ion current, and they propagate via the naturally formed softmaterial dielectric waveguides with the structure of "intracellular fluidlipid membrane -extracellular fluid" (17)(18)(19). Both experiments and simulations showed the electromagnetic pulse signal has limited transmission efficiency when propagating via the softmaterial waveguide pathway.…”

“…One possible way to enlarge L in is to increase the thickness of myelin sheath. Both simulation and experiments on large scale softmaterial waveguides showed that, in general the thicker the dielectric layer, the lower the attenuation and thus longer effective transmission length (17), which probably decides the internode length. This is consistent with observations in biosystems (24).…”