A predetermined electric current is supplied to coil by changing a pulse width of a voltage applied to the coil according to a current instruction value. The transparent chuck comprises a light-incident plane and a light-emitting plane. The collapsible unit is driven by an expansioncontraction mechanism to expand and contract relative to the fixed unit. Optionally, the elongated fiber includes one or more probes homogenously functionalized along its length that bind targeted biological materials. The common electrode is disposed over the first and the second pixel electrode.