Printed Electrochemical Sensors

This dissertation presents multiple electrochemical sensors to determine the level of hydrogen peroxide levels and monitor the cryopreservation processes. An ability to quantify chemical species such as hydrogen peroxide is crucial in many industries (e.g. healthcare, food processing, pharmaceutical, etc.), and monitoring the physical characteristic of samples during cryopreservation is essential for quality control purposes. Electrochemical sensors are good candidates for both of these applications due to their high sensitivity and selectivity. Fabrication methods based on automated printing technologies can provide alternative methods for the development of such electrochemical sensors. Utilizing these additive manufacturing techniques minimizes material waste during fabrication, which reduces the total cost of sensor. Also, the increasing consumer-level availability of the required equipment facilitates prototyping and customizing sensors. Regular inkjet printers were used to fabricate the amperometric electrochemical sensors for the determination of hydrogen peroxide. To improve the performance of the sensors, multi-walled carbon nanotubes and graphene oxide were used to develop an ink material compatible with regular inkjet printers. Also, to perform the electrochemical analyses a multi-channel portable potentiostat circuit was developed. This combination of sensors and portable electronic system could lead to fast and accurate on-site measurement of hydrogen peroxide at a low cost. Furthermore, impedance measurement can provide novel information about freezing and thawing processes, which play a crucial role in validating implementation of cryopreservation protocols. Printed circuit board (PCB) technology and 3-dimensional printing were employed to develop impedimetric sensing probes that were compatible with conventional containers used in cryopreservation. As seen above, a custom-made portable impedance measurement system was developed to use with the sensing probes in field settings. The exploitation of such probes and instrumentation for impedimetric monitoring of cryopreservation processes could increase the reproducibility of protocols and eventually can lead to much-needed standardization of these processes. This could also provide new types of quantitative information to assist theoretical understanding of cryobiology