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 crosslinking 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 degC 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.