title: Selective electroless and electrolytic deposition of metal for applications in microfluidics: fabrication of a microthermocouple.
abstract: This paper describes a general strategy for the fabrication of a microthermocouple based on the spatially defined electroless deposition of metal, followed by annealing and electroplating. We present scanning electron microscopy and atomic force microscopy characterizations of the deposition and annealing process, as well as the performance of the microfabricated Ni-Ag thermocouple. The temperature-voltage curve for this Ni-Ag microthermocouple is linear over the range 0-50 degrees C with a slope of 61.9 degrees C mV(-1). The sensitivity of our temperature measurement, which is limited by the uncertainty of our calibration curve, is approximately 1 degrees C. The optimum figure of merit (Z(opt)) is 1.0 x 10(-5) for this type of Ag-Ni thermocouple. We have fabricated microthermocouples ranging in size from 50 to 300 microm. The microthermocouple was integrated into microchannels and used to measure the in-channel temperature rise caused by the following: (1) a simple acid-base reaction, HCl + NaOH --> H2O + NaCl, and (2) an enzyme-catalyzed biochemical reaction, H2O2 + catalase --> H2O + 1/2 O2. We have also profiled the temperature increase in the presence of electroosmotic flow for a 100-, 200-, and 300-microm channel.
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Allen
authors.forename: Indalesio
authors.initials: I
authors.lastname: Rodriguez
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Kuyper
authors.forename: Robert M
authors.initials: RM
authors.lastname: Lorenz
authors.forename: Paolo
authors.initials: P
authors.lastname: Spicar-Mihalic
authors.forename: Jason S
authors.initials: JS
authors.lastname: Kuo
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Chiu