Inkjet-Printed Flexible Spin Seebeck Thermopile Device for Low-Cost Spintronics Device Fabrication

Spin-momentum-mediated heat–charge conversion technologies for developing thin thermoelectric generators and heat flow sensors have been extensively studied. The thermoelectric generation (TEG) based on the spin Seebeck (SSE) effect is a promising technology. In this study, a flexible SSE thermopile device is fabricated using inkjet printing with Fe₃O₄ and Ag nanoparticle (NP) ink. A square Fe₃O₄ NP and a wire-shaped Ag NP layer are used as the first and second layers, respectively. These layers are overlaid using inkjet printing twice. To obtain the SSE voltage (V_SSE), a thin Pt film is deposited on a printed thermopile device. SSE generators consisting of a Pt thin film/Fe₃O₄ NP layer are connected through a Ag NP wire to form a thermopile structure. The saturated V_SSE of the SSE thermopile device increases with the number of SSE generators. In addition, the SSE-TEG of an SSE thermopile device is observed using a heat source with a curved surface. In these results, it is indicated that the inkjet-printing fabrication method holds great potential in both the SSE thermopile devices and the flexible spintronic devices because it is a simple and fast process that does not require lithography.