title: Optoelectric patterning: Effect of electrode material and thickness on laser-induced AC electrothermal flow.
abstract: Rapid electrokinetic patterning (REP) is an emerging optoelectric technique that takes advantage of laser-induced AC electrothermal flow and particle-electrode interactions to trap and translate particles. The electrothermal flow in REP is driven by the temperature rise induced by the laser absorption in the thin electrode layer. In previous REP applications 350-700 nm indium tin oxide (ITO) layers have been used as electrodes. In this study, we show that ITO is an inefficient electrode choice as more than 92% of the irradiated laser on the ITO electrodes is transmitted without absorption. Using theoretical, computational, and experimental approaches, we demonstrate that for a given laser power the temperature rise is controlled by both the electrode material and its thickness. A 25-nm thick Ti electrode creates an electrothermal flow of the same speed as a 700-nm thick ITO electrode while requiring only 14% of the laser power used by ITO. These results represent an important step in the design of low-cost portable REP systems by lowering the material cost and power consumption of the system.
authors.affiliation: Birck Nanotechnology Center, School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
authors.forename: Avanish
authors.initials: A
authors.lastname: Mishra
authors.affiliation: Birck Nanotechnology Center, School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Khor
authors.affiliation: Birck Nanotechnology Center, School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
authors.forename: Katherine N
authors.initials: KN
authors.lastname: Clayton
authors.affiliation: Department of Mechanical Engineering, University of Louisville, Louisville, KY, USA.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Williams
authors.affiliation: School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, P. R. China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Pan
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
authors.forename: Tamara
authors.initials: T
authors.lastname: Kinzer-Ursem
authors.affiliation: Birck Nanotechnology Center, School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
authors.forename: Steve
authors.initials: S
authors.lastname: Wereley
mesh_terms: D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D008846:Micromanipulation / Q000379:methods*; D008962:Models, Theoretical; D061848:Optical Imaging / Q000379:methods*
keywords: Electrokinetics; Electrothermal; Manipulation; Trapping; Tweezers