CHIP REACTOR FOR MICROFLUID CALORIMETRY

A microchip module with integrated flow channel and highly sensitive t hin-film thermoelements of Bi0.87Sb0.13 and Sb was developed in order to realize a microcalorimeter for small volumes and flows in the mu l and mu l/min range, respectively. It was designed according to the pri nciple of flow-injection analysis (FIA) and prepared using means of mi cromachining technology The how channel comprises two inlets, a mixing region, a measurement region and one outlet. In this way, the initiat ion of chemical reactions by interdiffusion takes place in the closest possible contact with the sensing elements. Three thermopiles (i.e. t hermoelements connected in series) an arranged on a thin-film membrane covering the fluid channel. A thin-film heater of an NiCr alloy is in tegrated for internal electrical calibration. The microreactor was fir st tested in the neutralization reaction between sodium hydroxide and sulphuric acid for different NaOH concentrations, flows, and sample vo lumes, investigating for the present the integral signal of the three thermopiles connected in series. From the collected data, the minimum detectable power, minimum detectable NaOH concentration, and the react ion enthalpy were calculated. The results characterize the module as a sensitive chip calorimeter, showing the suitability of the micromachi ning technology for calorimetry. (C) 1998 Elsevier Science B.V.