<p class="MsoNormal" style="margin-bottom: .0001pt; text-align: justify; line-height: normal">Bioreactors are engineered physiological environment that can be used to study and grow tissue and organ systems <i>in vitro</i>. They are used to subject the cells to physiologically relevant stimulus such as tensile or compressive stress, bending, torsion or fluid flow. An optimal internal environment of a bioreactor should remain sterile while maintaining the viability of tissue, cells and biomolecules at 37°C (normal body temperature) with a tolerance of + or – 0.1 °C. In a previous study, a low-cost benchtop bioreactor was designed and fabricated for tissue engineering applications. There was a need to incorporate a temperature-controlled system to the bioreactor that could uniformly distribute the heat without harming the cells during the course of 7-15 days experiment. This study presents an Arduino microcontroller-based temperature-controlled system using an autotuning proportional integral derivative (PID) control for a small-scale bioreactor. A table top bioreactor temperature maintenance system has been designed, fabricated and assembled with laser cut acrylic. The enclosure consists of a heater with ducting to create adequate circulation by incorporating a supply fan that pushes the heat into the space and an exhaust fan that pulls the air across the space.&nbsp; This circulation will create good mixing that equally distributes the temperature in the enclosure. A servo motor on each side of the enclosure will drive a mechanism that actuates a door to open in the case of the temperature inside the enclosure increases past the specified set point. Four TMP117 high precision temperature sensors are used with I2C interface to read temperature value of the enclosure. A user interface has been designed using the LCD display and push button switches. A PID controller has been implemented on an Arduino Uno microcontroller with a closed-loop system. The&nbsp;PID loop uses the feedback from the TMP117 sensors and outputs a PWM signal to a MOSFET that controls the power of the heater.&nbsp;This low-cost temperature control bioreactor system creates an ideal environment for cellular growth. It prevents development of hot spots that can result in cell death and eventual failure of the experiment. In future, the device can be extensively used to study and test cellular interaction with its physical microenvironment, relevant to cell and tissue engineering. The user interface will let a user set any temperature value within a predefined range and the PID Controller will be autotuned to maintain that temperature constant inside the enclosure. &nbsp;Since the temperature control can vary and monitor fine changes in the environment, this can be a tool to study impact of temperature variation of cell response such as growth and differentiation.</p>

Bioreactor Temperature Control System Using PID Controller

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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