Printable sensor technology for automated verification of best-before dates and cold chain monitoring in the retail sector
Short name: Printable RFID sensors
Fogra no. 64.024
Project leader: Dr P. Stolper
Partner: wfk – Cleaning Technology Institute e.V., Krefeld
Funding: BMWK (IGF) via DLR
Timescale: 01.04.2026 - 31.03.2028
Food waste is a global problem. Temperature-sensitive goods such as meat, fish, dairy products, ready meals and frozen goods are particularly affected. These products are especially susceptible to quality loss if the cold chain is interrupted or not properly maintained. Furthermore, monitoring best-before dates (BBD) poses a major challenge for retailers in terms of inventory management and quality assurance.
Particularly for temperature-sensitive goods, adherence to BBDs is crucial for product safety, customer satisfaction and the prevention of economic losses. In practice, BBDs are often checked manually by staff, who must regularly spend considerable time checking shelves and stock levels. A lack of transparency regarding remaining shelf life often leads to delayed price reductions.
Solution steps
The following steps are necessary to achieve the targeted results of the research project:
- Development of eutectics with optimized melting temperatures
- Selection and characterization of conductive additives
- Selection and characterization of the polymer matrix for the thermosensitive resistor
- Development of printing conditions at temperatures of approximately -30°C
- Development of optimal antenna structures with thermosensitive resistors
- Development of a customized readout system for the antennas
- Field testing of the developed structures
Targeted results
The aim of this research project is to develop printable, chip-free, passive RFID transponders for the automated monitoring of foodstuff. The RFID transponders consist of several antennas, for example, arranged concentrically and tuned to different frequencies. Each antenna encodes one bit. With a sufficiently large number of antennas, a best-before date can be encoded in a small area (e.g. 1 cm x 1 cm). To monitor the cold chain, a special antenna is being developed that contains a temperature-sensitive resistor, enabling detection of when a defined temperature is exceeded: a change in resistance results in a permanent change in the read-out signal (e.g. by altering the length of the antenna to be excited). This allows the interruption of the cold chain to be traced at any later point in time.
The temperature-dependent resistor consists of a polymer matrix containing particles with a defined melting temperature (eutectic particles). Conductive components are embedded within the eutectic particles. This embedding prevents interactions between the conductive components. The melting temperature of the eutectic particles is selected to correspond to the lowest, no longer tolerable temperature in the product-specific cold chain that must be maintained. Consequently, an interruption in the cold chain causes the eutectic particles to melt. Upon melting, the eutectic spreads throughout the entire polymer network of the temperatureswitchable resistor, causing the conductive components to come into contact with one another across the entire resistor and thus increasing the resistor’s conductivity.