Abstract
In this paper, the development of a copper–chrome-based glass microheater and its integration into a Polymethylmethacrylate (PMMA) microfluidic system are presented. The process highlights the importance of an appropriate characterization, taking advantage of computer-simulated physical methods in the heat transfer process. The presented system architecture allows the integration for the development of a thermal flow sensor, in which the fluid flows through a 1 mm width × 1 mm length microchannel across a 5 mm width × 13 mm length heating surface. Using an electrothermal analysis, based on a simulation and design process, the surface heating behavior curve was analyzed to choose a heating reference point, primarily used to control the temperature point within the fluidic microsystem. The heater was characterized using the theory of electrical instrumentation, with a 7.22% error for the heating characterization and a 5.42% error for the power consumption, measured at 0.69 W at a temperature of 70 °C. Further tests, at a temperature of 115 °C, were used to observe the effects of the heat transfer through convection on the fluid and the heater surface for different flow rates, which can be used for the development of thermal flowmeters using the configuration presented in this work.
Highlights
Heating in microsystems, referred to as microheaters, has a fundamental role in the operation of different devices, such as thermal flow sensors [1], microelectromechanical systems (MEMS) gas sensors [2,3,4,5], liquid petroleum sensing (LPG) [6], trace detection of explosives [7], thermal electric generation on microchannels [8], and temperature control of environment for chemical and biological processes at small scales [9,10]
The design of temperature controls directly integrated into the microsystem architecture [12] is an auspicious alternative that has been credited for biological monitoring microsystems [10,13], polymerase chain reaction integrated devices [14], protein characterization and sensing [15], and supported bilayer lipid membrane-based biosensors [16], among others
The common theoretical resistance calculated in this work was less than the practical resistance measured with respect to the heater, which is related to the effects of resistivity on thin films that should be considered with a different model
Summary
Heating in microsystems, referred to as microheaters, has a fundamental role in the operation of different devices, such as thermal flow sensors [1], microelectromechanical systems (MEMS) gas sensors [2,3,4,5], liquid petroleum sensing (LPG) [6], trace detection of explosives [7], thermal electric generation on microchannels [8], and temperature control of environment for chemical and biological processes at small scales [9,10]. The design of temperature controls directly integrated into the microsystem architecture [12] is an auspicious alternative that has been credited for biological monitoring microsystems [10,13], polymerase chain reaction integrated devices [14], protein characterization and sensing [15], and supported bilayer lipid membrane-based biosensors [16], among others. These microsystems employ a thin film of deposited metal as an electrically resistive heating element, as described by Joule’s law. The importance of having direct contact between the heater and the system relies on having control and certainty about the conditions of the elements immersed in the microsystem, due to a resistance reduction in the heating transference [17], in addition to having the possibility to include thermal sensors using similar thin-film technologies within an integrated system [18]
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