A floating portable humidifier is configured to float partially submerged in an open tray of water. The rail has a top wall, a bottom wall and a sidewall connected between the top and bottom walls. 70 \u03bcm, the average particle diameter being obtained by observation using a scanning electron microscope. A first write line is separated from the first read line by a first insulator and a second write line is separated from the second read line by a second insulator.