A microelectrode was fabricated by electrochemical etching of a pencil lead (0.5 mm in diameter) in 1.0 M NaOH aqueous solution. The pencil lead was dipped into the solution and then an ac voltage (3.0 V-rms for 10 min) was imposed against a stainless plate under mild stirring (450 rpm). The electrochemically sharpened pencil tip was about 10 mu m in diameter (12 +/- 3 mu m, n = 5), and the lateral part was insulated within a polypropylene micro-pipette tip (2-200 mu L volume range). The cyclic voltammograms conducted in 2.0 mM ferricyanide/ferrocyanide buffer solution (pH 7.0) are with low capacitive current and a typical sigmoidal signal of micro-sized electrodes. The microelectrode was used to perform dielectrophoresis of polystyrene latex microbeads (nominal diameter of 3 mu m) and human red blood cells. A conducting glass (indium tin oxide coated glass, 40 mm x 40 mm x 1 mm) served as the counter electrode (0.5 mm beneath the microelectrode) to generate the asymmetrical electric field and also as the window for microscopic observation. With the sinusoidal bias voltage (30 V-rms) ranged from 20 Hz to 2 MHz, positive and negative dielectrophoretic phenomena were identified. (C) 2011 Elsevier Ltd. All rights reserved.