It is not just in the area of ‘active’ material technology, such as colour-changing films, that condition monitoring can be found. Electronic sensors can often offer more precise results as well as recording the actual levels and speed of deterioration as well as humidity to offer further insights into this area. Here are two very smart examples.

University teams based in various academic institutions in Ohio, USA and Quingdao in China were concerned that as the use of sensors to monitor food condition has and continues to increase the need for sustainable power sources to drive them has also grown. Their starting point was that traditional batteries have limited lifetimes and can contribute to environmental pollution. So a self-powered intelligent packaging system that uses sustainable energy is highly desirable.

The group explored the use of triboelectric nanogenerators (TENGs), which convert mechanical energy into electricity and are based on the coupled effect of triboelectrification and electrostatic. These seem to offer advantages, such as easy fabrication, diverse material options, low cost, and being lightweight. The researchers combined these generators with desiccants, which absorb humidity within a package and which are a common component in food, pharmaceutical and electronics packaging.

The study demonstrates that a desiccant-based triboelectric nanogenerator (D-TENG) that harvests energy from vibration during the transportation of packaged products and uses it as a power source can be used in intelligent packaging systems. The D-TENG uses desiccants as the freestanding triboelectric material and stores them in honeycomb holes made of paperboard. The device operates in a contact-separation mode based on triboelectrification between the desiccants and PTFE films.

The scientists systematically investigated the significant factors that affect the D-TENG’s energy harvesting performance, including the type of desiccants, frame height and number of honeycomb holes. In addition, they studied the effects of vibration frequency, amplitude and orientation angle. Finally, they claim to have developed a self-powered integrated smart packaging system that monitors the temperature and humidity of packaged goods.

In another sensor project in New Zealand, researchers have harnessed the power of near-field communication (NFC) tags to create a dual-channel sensor tag that can be used in smart packaging for the quality monitoring of fresh produce, such as bananas, by tracking temperature and ethylene concentration in the storage/transport environment

As most of these kinds of wireless sensor tags have been used for single-sensing applications the group designed a printed circuit board (PCB) module (13 × 13mm) for NFC-enabled sensor tags with both electrical resistance and capacitance read-out channels that offer dual-channel sensing.

A light-energy-harvesting NFC patch for temperature sensing during cold food storage has been developed, but most of its major components were not fully integrated into the flexible patch but just connected to it via hard wires. In other flexible NFC sensors the majority of the electronic components such as the temperature sensing IC, ph and load cell were connected to the antenna by soldering, they say. The group wanted to make this a fully integrated sensor.

As part of their wireless sensor tag, a square antenna pattern was printed directly on a flexible PET substrate and integrated into the PCB module to demonstrate a dual-channel temperature and ethylene gas sensor. These sensors were printed using a positive temperature coefficient ink and a tin oxide (SnO2) nanoparticle ink, respectively.

This article was created in collaboration with AIPIA (the Active and Intelligent Packaging Industry Association). For a full update on active and intelligent packaging, come along to the AIPIA World Congress (co-organized by Packaging Europe) in Amsterdam on 14-15 November. The only smart packaging event covering the entire technology spectrum, the World Congress is a meeting place for the global active and intelligent packaging industry where brand owners, innovators, and other stakeholders can network and see and discuss the latest trends and innovations. Register to attend here.