An electric component connection mechanism of a fuel cell stack includes a fuel cell stack body, terminal plates, end plates, and a housing. In one embodiment, a substrate processing apparatus includes a processing chamber, a substrate holder inside of the processing chamber for holding a substrate, and a sonic box in the processing chamber for supplying sonic waves substantially perpendicularly to the substrate. A fusion of droplets in electric fields is also described. A sensor may be also provided to detect the relative concentration of Pt+2 ions to Pt+4 ions and to tailor the relative concentrations to a predetermined level. When an operation force is applied to the first arm, the first arm is moved to drive the second arm so as to make the elastic unit store energy.