A Low Cost Stirring Platform with Integrated Temperature Control Scheme for Microbioreactor Operation

In this paper, we presented the establishment of a cheap and simple stirring platform integrated with on/off temperature controller for microbioreactor operation. The stirring platform was designed to provide necessary mixing via magnetic stirrer bar for a microbioreactor setup. The microbioreactor (volume ~ 300 mL) used in this investigation was fabricated out of the poly(methylmethacrylate) (PMMA) polymer material via micromachining. The reactor was deliberately designed to work under bubble-free conditions and limited only to batch operation. The paper first described the details of the mechanical design of the stirring platform and the microbioreactor prototype used in the work. These include the dimensions of the reactor and the stirring platform, positioning of the sensors and actuators employed, wiring connections, and the process control algorithm. Secondly, experimental results obtained to assess the mixing quality of the reactor and to characterize the performance of the controller (stirring and temperature) in terms of control accuracy and system responses were presented. We show that by implementing a rather straight forward control algorithm, the mixing quality and the temperature of the microbioreactor can be accurately controlled within an acceptable range of the set point values and provide a good response (i.e. in the range of few seconds). Results also showed that (1) at agitation rate of 300 rpm, mixing time as fast as 3 seconds was obtained and (2) reactor temperature can be tightly controlled at ±0.15 o C of the set point value.