A 4 × 4 array multichannel magnetic stimulation system using submillimeter sized planar square spiral coils: The spatial distribution of electromagnetic field

Multi-coil magnetic stimulation has advantages over single-coil magnetic stimulation, such as more accurate targeting and larger stimulation range. In this paper, a 4 × 4 array multichannel magnetic stimulation system based on a submillimeter planar square spiral coil is proposed. The effects of multiple currents with different directions on the electromagnetic field strength and the focusing zone of the array-structured magnetic stimulation system are studied. The spatial distribution characteristics of the electromagnetic field are discussed. In addition, a method is proposed that can predict the spatial distributions of the electric and magnetic fields when currents in different directions are applied to the array-structured magnetic stimulation system. The study results show that in the section of z = 2 μm, the maximum and average magnetic field strengths of the array-structured magnetic stimulation system are 6.39 mT and 2.68 mT, respectively. The maximum and average electric field strengths are 614.7 mV/m and 122.82 mV/m, respectively, where 84.39% of the measured electric field values are greater than 73 mV/m. The average magnetic field strength of the focusing zone, i.e., the zone in between the two coils, is 3.38 mT with a mean square deviation of 0.18. Therefore, the array-structured multi-channel magnetic stimulation system based on a planar square spiral coil can have a small size of 412 μm × 412 μm × 1.7 μm, which helps improving the spatial distribution of electromagnetic field and increase the effectiveness of magnetic stimulation. The main contribution of this paper is a method for designing multichannel micro-magnetic stimulation devices.

Self-Inductance Calculation of the Archimedean Spiral Coil

In this paper, a new method to calculate the self-inductance of the Archimedean spiral coil is presented. The proposed method is derived by solving Neumann’s integral formula, and the numerical tool is used to calculate the inductance value. The calculation results are verified with several conventional formulas derived from the Wheeler formula or its modified form and 3D finite element analyses. The comparison with simulation results shows that the conventional formula has an error of above 40% compared to the proposed method, which has below 7% when the wire diameter is reduced. To further check the validity, different sizes of the spiral coil are fabricated by changing the geometrical parameters such as the number of turns, turn spacing, inner radius, outer radius, and wire diameter. Litz wire is chosen for making the spiral coil, and bobbins are made using a 3D printer. Finally, the calculation results are compared with the experimental result. The error between them is less than 2%. The comparison with the conventional formulas, simulation, and measurement results shows the accuracy of the proposed method. This method can be used to calculate the self-inductance of wireless power coils, inductors and antenna design.

Thermal Performance Improvement of Solar Parabolic Dish System Using Modified Spiral Coil Tubular Receiver

The present research intends to design an efficient receiver for solar thermal applications with a solar dish concentrator system. Thermal and dynamic analysis is carried out for different convolutions of a spiral coil, and experiments are performed for testing the modified absorber. Experimental results are validated for the spiral absorber with numerical results. Three receivers of different numbers of convolutions are analyzed, and simulation steps are performed for these receivers to make improvements in the system efficiency. Finally, 5 convolutions of a spiral coil tubular absorber are taken for the modified design of the system. Absorber position for every spiral convolution is kept at the focus of the concentrated solar dish collector to achieve maximum efficiency. Material used for the reflective surface is anodized aluminum and copper for the absorber. The diameter of the aperture for the parabolic dish collector is 1.4 m. The maximum absorber temperature for May month comes out to be 296°C, and the maximum working fluid outlet temperature is found to be 294.2°C which is near to simulating temperature of 289.59°C and 288.15°C, respectively. This innovative design of the absorber consists of a feature of a 5 mm extension to the spiral tube at the exit and entry; hence, the turbulence effect could be overcome. Experimental thermal efficiency was found the highest (i.e., η th max = 75.98 % ) for May. This work emphasizes on improving thermal performance by obtaining optimum absorber size using convolution strategy. Investigation of 5 convolutions of spiral coil tubular absorber with extended ends for obtaining optimum performance than existing work is the superiority of this work.

Printed Split-Ring Loops with High Q-Factor for Wireless Power Transmission

The use of printed spiral coils (PSCs) as inductors in the construction of Wireless Power Transmission (WPT) circuits can save space and be integrated with other circuit boards. The challenges and issues of PSCs present for WPT mainly relate to maintaining an inductive characteristic at frequencies in Ultra High Frequency (UHF) band and to maximising the power transfer efficiency (PTE) between primary and secondary circuits. A new technique is proposed to increase the Q-factor relative to that offered by the PSC, which is shown to enhance WPT performance. This paper provides four-turn planar split-ring loops with high Q-factor for wireless power transmission at UHF bands. This design enhances the power transfer efficiency more than 12 times and allows for a greater transfer distance from 5 mm to 20 mm, compared with a conventional planar rectangular spiral coil.

Inductive power transmission through printed sprial coils for seizure application

This thesis proposes a realistic model for transcutaneous inductive power link for seizure applications using PSCs (Printed Spiral Coils). The benefit of this model is smaller size implanted coil compared to its counterparts while maintaining high loaded system efficiency. The introduced Printed Spiral Coil (PSC) geometric parameters are achieved using MATLAB that searches for the highest efficiency of the inductive coil within the given constraints. The output from the MATLAB simulation is used to created optimum design in AMDSpro tool and is verified. The outer diameter of the implanted coil is introduced to be d₀₂ = 6mm while the simulated efficiency is calculated as η [subscript] sim = 46.67% operating at f [subscript] sim = 2.52MHz for the relative distance of D = 10mm filled with layers of modeled human skull (Outer Compact Layer, Spongiosum, and Inner Compact Layer). The coupling coefficient of the spiral was calculated to be k = 0.69. The implanted PSC is associated with load capacitance and resistance of R [subscript] L = 4.5Ω and C [subscript] L = 95nf.

Inductive power transmission through printed sprial coils for seizure application

This thesis proposes a realistic model for transcutaneous inductive power link for seizure applications using PSCs (Printed Spiral Coils). The benefit of this model is smaller size implanted coil compared to its counterparts while maintaining high loaded system efficiency. The introduced Printed Spiral Coil (PSC) geometric parameters are achieved using MATLAB that searches for the highest efficiency of the inductive coil within the given constraints. The output from the MATLAB simulation is used to created optimum design in AMDSpro tool and is verified. The outer diameter of the implanted coil is introduced to be d₀₂ = 6mm while the simulated efficiency is calculated as η [subscript] sim = 46.67% operating at f [subscript] sim = 2.52MHz for the relative distance of D = 10mm filled with layers of modeled human skull (Outer Compact Layer, Spongiosum, and Inner Compact Layer). The coupling coefficient of the spiral was calculated to be k = 0.69. The implanted PSC is associated with load capacitance and resistance of R [subscript] L = 4.5Ω and C [subscript] L = 95nf.