Chip reactor for microfluid calorimetry

A microchip module with integrated flow channel and highly sensitive thin-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 principle of flow-injection analysis (FIA) and prepared using means of micromachining technology The how channel comprises two inlets, a mixing region, a measurement region and one outlet. In this way, the initiation of chemical reactions by interdiffusion takes place in the closest possible contact with the sensing elements. Three thermopiles (i.e. thermoelements connected in series) an arranged on a thin-film membrane covering the fluid channel. A thin-film heater of an NiCr alloy is integrated for internal electrical calibration. The microreactor was first tested in the neutralization reaction between sodium hydroxide and sulphuric acid for different NaOH concentrations, flows, and sample volumes, 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 reaction enthalpy were calculated. The results characterize the module as a sensitive chip calorimeter, showing the suitability of the micromachining technology for calorimetry. (C) 1998 Elsevier Science B.V.