## 1 Introduction
The application of the magnetic field causes the Fe\({}_{3}\)O\({}_{4}\) and metal particles to aggregate, and magnetic clusters are created in NR-latex type as well as silicon-oil type MCF rubber. In general, water involved in NR-latex plays an important role in electric conductivity, which is based on ionic conduction. Therefore, owing to the filler and the water role, electric conductivity is superior to that of PSECR. Furthermore, as shown in a previous investigation, NR-latex type MCF rubber has been evaluated the following technical cases as a physical value: surface roughness of a hard plate surface with coarse or smooth roughness in the range of \(R_{a}\) = 0.19-20.86 \(\upmu\)m, which is related to finishing in precision machinery industry; softness of a soft surface of texture of clothes, paper, gel, etc. ; geometric shape of concave and convex surface less than 5.7 mm in height, which is related to the evaluation of a biological surface such as a fish, insect, etc. NR-latex type MCF rubber made by the DM, however, has a problem in that deterioration occurs in a short period of about a week. In addition, it has electrical resistivity on the order of 1 \(\Omega\cdot\)m [22], which does not provide high enough sensitivity to fulfill the requirements for a skin sensor. [PERSON] has proposed a new method (NM), which involves solidifying rubber using both magnetic and electric fields. The rubber liquid is poured between electrodes, and a magnetic field is applied. NR-latex without MCF is created as a thin film, and its thickness does not increase even with an extended application of the electric field. With NR-latex MCF rubber, however, since the magnetic field is applied along the same direction as the electric field line, the thickness increases substantially due to the magnetic clusters. When the electric field or magnetic field is used alone, the electrical property is less sensitive than with both, and the mechanical property is less extensible. These characteristics have been shown in the case of a narrow electrode gap of 1 mm in previous studies [22]. It was also clarified that NR-latex MCF rubber made with NM maintains a smaller electrical resistivity on the order of \(10^{-2}-10^{-3}\)\(\Omega\cdot\)m from its creation to a period of more than a year. The NM is a noteworthy and effective production method for avoiding deterioration due to aging. However, how enhancement of MCF rubber thickness is affected by various strengths of the electric and magnetic fields has not yet been clarified. While the effect of the magnetic field on electrolytic polymerization is significant, parameters including the magnetic field distribution and magnitude have not yet been elucidated. In particular, the phenomenon of how MCF rubber is enhanced by both fields at a large electrode gap remains unknown. Investigating the enhancement of MCF rubber at a large electrode gap is related to clarifying the configuration of the enhancement. Therefore, in the present paper, we first investigate the effect of the magnetic field on the metamorphosis of MCF rubber by electrolytic polymerization. On the other hand, magnetic clusters in the filler play a very significant role in the solidification of MCF rubber with the NM. Controlling the applied magnetic field allows the magnetic clusters to grow freely in the filler. In terms of whether the filler is magnetic or conductive, there have been many studies on the use of polymers such as polymethyl methacrylate (PMMA). Carbon nanotubes is another well-known filler [23]. The properties of a sensor can be controlled by the alignment of the carbon nanotube with a magnetic field. The idea and concept of embedding fillers of carbon nanotubes in a polymer is similar to that of the MCF rubber. Only the material of the solvent and substrate is different. There has been research that looked at carbon nanotube in NR-late [24; 25; 26; 27; 28]. Most of these studies, however, did not consider the alignment of the filler with the aid of a magnetic field.