Dr. Ruoxi (Rachel)Ma is an assistant professor in the Department of Graphic Communication at Cal Poly. Rachel received her Ph.D. degree in Paper and Printing Science from Western Michigan University. Her research interests include inks and substrates interactions, biodegradable packaging materials, and applications of printed electronics on smart packaging. Currently, she is teaching undergraduate classes, including Substrates, Inks and Toners, Offset and Digital Printing Methods, and Senior Project. She also severs as the advisor for TAGA Student Chapter at Cal Poly.
Screen Printed Moisture Sensor and Its Application On Smart Packaging
Ruoxi Ma, California Polytechnic State University; Alexandra Pekarovicova, Western Michigan University
The hemicellulose–based suspension with nano–fibrillated cellulose (NFC) composite film exhibit outstanding air barrier properties, which supports their applications as bio–based and biodegradable barrier coating on food packaging materials. The hydrophobic property of the hemicellulose–based biopolymer has been greatly improved (MVTR decreased by 49.7%) with cross linking by using citric acid.
In this work, the crosslinked bio–polymer suspension was applied on solid bleached sulphate (SBS) board with a Meyer rod. Interdigitated electrodes were designed as moisture sensors and then screen printed on the coated SBS board with silver conductive ink. The hemicellulose–based barrier coating layer functioned as a moisture sensing layer. The printed sensor device was calibrated with its absorption and desorption isotherms at 23 °C with the range of relative humidity 20%–80%, followed by characterizations of the sensor’s impedance change with each moisture level ranging from RH 20% to 80%. The breakthrough time was observed for each level of RH by measuring impedance using the LCR meter.
These findings point to the opportunity of coupling the hemicellulose–based barrier coatings with printed moisture sensors in order to boost their capabilities as smart barrier packaging materials.