## 1 Introduction  
Sensors require haptic sensibility in rubber under normal or shear motions, including sensibilities to temperature or photoreaction. The haptic sensibility that is provided to robots predominantly corresponds with sensing normal or shear forces and temperature [1; 2; 3]. These sensibilities are related to the five types of touch sensations in the human skin: tactile, baresthesia, algorometry, warm, and cold [4]. When sensibility is incorporated into the skin of a robot, the material that is feasible to the outer artificial skin installed on it is termed sensitive skin, smart skin, or electronic skin (E-Skin) [5]. As an alternative artificial skin, the authors have also proposed a hybrid skin (H-Skin) with multiple functionalities, including flexibility, thermo-sensitivity, photovoltaics, and ability to sense modalities to its forces [6; 7; 8]. H-skin is produced by a new method using solidified rubber by electrolytic polymerization, together with the configuration of magnetic clusters of metal particles integrated into the rubber by the application of a magnetic field [9; 10; 11]. The resulting material is named magnetic compound fluid (MCF) rubber. This novel solidification method differs from the conventional vulcanization technique, where sulfur is used on the field for the normal production of solid rubber [12]. However, in the case of MCF, it possesses nm-ordered magnetite (Fe\({}_{3}\)O\({}_{4}\)) particles that are obtained using a magnetic fluid (MF) during compounding, and \(\upmu\)m-ordered metal particles, such as Fe and Ni. Because it is an effective magnetic-responsive intelligent fluid, MCF has been proposed as an alternative in many engineering applications, such as dampers and polishing machines [13]. By applying a magnetic field on the MCF rubber during electrolytic polymerization, the magnetic particles of MCF are fabricated as heterostructures like in many needle-like clusters so that the electric and photovoltaic properties of MCF rubber are enhanced, as well as its mechanical and electrical properties becoming anisotropic. Furthermore, to fabricate an MCF rubber sensor, a novel adhesion technique between rubber and metal has been proposed with hydrate-containing fabricated metallic or non-metallic elements under electrolytic polymerization to adhere plate- or wire-type electrodes to the rubber without the occurrence of detachment caused by large tension [14]. On one hand, the rubber that has been provided with electrolytic polymerization is water-soluble, which includes natural rubber (NR) and chloroprene rubber (CR) categorized as diene rubber. On the other hand, the water-insoluble rubber, silicone rubber (Q), can be electrolytically polymerized to be solidified together with water-soluble rubber such as NR or CR by mixing polyvinyl alcohol (PVA) as a surfactant or an emulsifier [15]. However, the authors have dealt with the combination of Q, NR, CR, PVA, and water-base MF alone until recent [15]. Other diverse combinations must be managed for example, the combination of water-insoluble rubber and water-insoluble MF, water-soluble rubber and water-insoluble liquid, that of other emulsifiers, and so on, which are not elucidated yet. It is critical to validate the practicability of electrolytic polymerization for the solidification of rubber with various combinations because the production of solidified rubber is convenient, whichever diverse kinds of rubber and MF are used. From point of view of other researches to have been conducted on so far, it is significant to develop the emergence of rubber blends by mixing two or more than polymers together in the field of polymer and rubber sciences so that many investigations have been conducted on, for example, by combining water-soluble and insoluble rubbers [16]. Carbon black or nanotube as well as ethylene-propylene-diene rubber (EPDM) has been often used, and the former was for its reinforcement of the rubber [17]. The method how to solidify these rubbers was the vulcanization with sulfur.