[Left] Schematic of a DG FET, [middle] SEM image of a cross-section of SiNWs fabricated on a silicon-on-insulator wafer and [right] change in the response voltage of planar and SiNW pH sensors for a wide range of pH (3–10). (c)2016 Cheol-Min Lim, In-Kyu Lee, Ki Joong Lee, Young Kyoung Oh, Yong-Beom Shin and Won-Ju Cho.