Rahim Rahimi1
Purdue University1
The global food packaging market is a 311.4-billion-dollar industry in 2020 and is estimated to reach 456.6 billion dollars by 2027. The rising demand for food packaging systems is accompanied by an increasing need for improving food quality and guaranteeing food safety. Monitoring the quality of packaged food is an important step in reducing food spoilage and improving food quality and food safety. Since humidity levels inside a package, pH, and chemical changes of meat products are good indicators of food quality, several sensors such as colorimetric sensors and active sensors have been developed to monitor them. While colorimetric sensors are cheap and can be easily embedded into transparent packages, they cannot be used for non-see-through packages and require laborious and time-consuming manual inspection. Although active sensors support automation in reading the sensors, they are expensive and not always biocompatible due to the presence of batteries and electronic chips in the sensors. Battery-less chipless wireless sensors have been widely used in food packaging because of their low cost, and wireless sensing capability. However, the main drawbacks in commercializing chipless sensors are the issues associated with their manufacturing process. Scalable manufacturing techniques such as printing techniques have been widely used for chipless sensors used in moisture sensors, soil sensors, and ID applications. Scalable manufacturing techniques provide a substantial reduction in the number of processes and resources required for manufacturing sensors. However, it introduces tremendous challenges such as the ink formulation for conductive and functional patterns, the need for custom-made screens, and the time required in the drying and sintering processes.<br/>In this talk, I will present an array of roll-to-roll laser assisted surface modification and micromachining strategies with two commonly used CO2 and Nd:YAG lasers that can significantly reduce manufacturing costs, increase efficiency, and improve the production rate of wireless sensors for use in food packaging applications. In the first section, I will describe the use of localized CO2 laser irradiation to selectively convert thermoset polymer films (e.g., polyimide) into electrically conductive and highly porous carbon micro/nano structures. This process provides a unique and facile approach for direct writing of carbon-based conductive patterns on flexible polymer sheets in ambient conditions, eliminating complexities of current methods such as expensive CVD processes and complicated formulation/preparation of conductive carbon-based inks used in inkjet printing. In the second part of the talk, I will demonstrate the use of laser ablation for selective patterning of conductive coatings from multilayer films such as ITO-coated PET and metalized paper and plastics as a simple and scalable alternative to conventional photolithography-based processes. I will finally discuss our on-going efforts in utilizing roll-to-roll laser processing approaches to create cost effective wireless sensors that can monitor the food packaging quality and freshness.