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Smart time temperature integrating label based on doping front migration

Identification

Key words doping front migration, smart label, self-writing, RFID, conductive polymer, chemical doping, time temperature exposure, intelligent packaging, time temperature integrator, TTI
Latest version 2010/12/13
Completed by KU Leuven LFT

How does it work?

Primary objective To monitor and communicate information on food quality using analogue and digital functions
Working principle This label is based on intrinsically conductive polymers with electrochromic behaviour (i.e. they change colour when energized by an electrical current). Doping is the process of intentionally introducing impurities into a semiconductor to change its electrical properties.

The label is actually a sandwich structure comprising an activation layer consisting of a thin film of conducting polymer on a flexible substrate and a migration layer, partially covered by an encapsulation layer and containing an electrolyte. The exposed migration layer can absorb water, resulting in an interaction between the electrolyte in the migration layer and the activation layer. In turn, this chemical (by base or acid) or electrochemical (by redox reaction) doping changes at the surface of the activation layer causes a colour change, displaying a moving front corresponding to the diffusion occurring in the migration layer. Migration length of the doping front is dependent on time and temperature. Therefore, the smart label can be used as a time-temperature integrator.

Images
Additional effects This label does not require powering device for RFID.
Important process parameters
Important product parameters Product: moisture content

Packaging: Gas permeable membrane in packaging is required to allow water vapour to come into contact with the migration layer of the label.

What can it be used for?

Products Packaged high-moisture foods for chill chain.
Operations Packaging. This low-cost devices using doping front migration could be the basis of a new class of smart labels for applications such as electronic “best before” labels on food and drink.
Solutions for short comings This tool answers to the need of inexpensive electronic “best before” labels. This innovation also does not require energy from a battery.

What can it NOT be used for?

Products Products packed in packages that do not allow transfer of water vapour.
Operations No information available on resistance of this label to processing.
Other limitations Temperature dependence of doping front migration rate should match the temperature dependence of growth of spoilage microorganisms. At this point, no clear information is available on the temperature dependence of doping front migration rate.
Risks or hazards No information available

Implementation

Maturity Available at labscale
Modularity /Implementation Modular
Consumer aspects No information available. No problems expected.
Legal aspects No information available. Please check local legislation.
Environmental aspects No information available. No problems expected.

Further Information

Institutes WWU Münster - Physics
Companies PolyTaksys
References 1. Knoll, M. (2008) A self-writing smart label based on doping front migration. Electrochimica Acta 54, 216-219.

2. Hermes, J.P. & Knoll, M. (2009) Doping front migration in intrinsically conductive polymers and its application. Electrochimica Acta 54, 4258-4261.

3. Yam, KL; Takhistov, PT; Miltz, J (2005) Intelligent packaging: concepts and applications. J Food Sci 70, R1-R10.

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Created by LiesbethV on 15 July 2011, at 13:43