Printed electronics could be edible in the near future, study shows

Printed electronics are a new device platform, but they are showing up in many places. The latest is in designing electronic sensors that could be used to detect whether or not frozen foods have been thawed and then refrozen, or to what degree they might have thawed during transport to a grocery store freezer.

Experts from ACS Sensors have written about working on edible sensor electronics, that could help tell when food has been tainted or refrozen, which could have severe consequences.

The MarketPlace

The printed electronics market is heating up, with a $53.5 billion revenue stream in 2021, and is set to reach $103.8 billion by 2027. That is a growth rate of 16.56% from 2022 to 2027, just five years.

The markets surrounding printed electronics are swelling at the thought of printed circuits and sensors in all kinds of devices, including, wearable devices, biosensors, skin patches, photovoltaic cells, and a host of other hardware.

ACS Sensors concept of edible sensor

The experts at ACS have said that many times sensors can be printed that have very practical and helpful uses in the human and animal worlds.

The idea that a sensor could be printed that would let a shopper know if meat was thawed, then refrozen, an occurrence with health risks. The ACS Sensor team has developed an edible sensor, made from food-grade materials, such as salt, red cabbage and beeswax, that can let a person know if food has been thawed, then refrozen.

How the edible sensor was created

To create a sensor for frozen products, one solution could be to use materials with electrical properties that are altered upon melting. It would also be optimum if such a change were to signal the occurrence in some way, such as a color change. In addition, an edible electronic device, which only uses food and consumable components would be the safest way to monitor food.

Ivan LLic, Mario Caironi, and a team at ACS Sensors set out to develop the first fully edible sensor, which was a self-powered temperature sensor with a clearly visible color indicator for use with frozen products.

Foods the produce electricity

The researchers started with designing and building a device that generated electrical current as it defrosted. They connected magnesium and gold electrodes through an electrolyte solution held in a plastic container.

The device was tested in frozen edible electrolyte solutions, including table salt and calcium-containing salts, as well as naturally electrolyte-rich foods, including a grape, melon, and apple. The solution was allowed to defrost, and they conducted a current between -58F and 32F, which the researchers say would be fine-tuned, based on the amount and type of salt.

The indicator is cabbage juice

The next phase was to connect the device to a color-changing system. This contained tin and gold electrodes and red cabbage juice. When activated by an electric current the juice would turn from its reddish-purple color to a distinct blue, that could not be reversed.

Packaging the sensor

The final step in the creation process was to put all the parts in a block of beeswax. The device held the temperature-activated and indicator solutions in separate chambers. This demonstrated that the self-powered device could be used for frozen food monitoring.

Proof-of-concept

This proof-of-concept sensor researchers say, paves the way for edible materials to be used in inexpensive, safe technologies that can alert consumers to a frozen products storage history.

Abstract

Improper freezing of food causes food waste and negatively impacts the environment. In this work, we propose a device that can detect defrosting events by coupling a temperature-activated galvanic cell with an ionochromic cell, which is activated by the release of ions during current flow. Both the components of the sensor are fabricated through simple and low-energy-consuming procedures from edible materials. The galvanic cell operates with an aqueous electrolyte solution, producing current only at temperatures above the freezing point of the solution. The ionochromic cell exploits the current generated during the defrosting to release tin ions, which form complexes with natural dyes, causing the color change. Therefore, this sensor provides information about defrosting events. The temperature at which the sensor reacts can be tuned between 0 and −50 °C. The device can thus be flexibly used in the supply chain: as a sensor, it can measure the length of exposure to above-the-threshold temperatures, while as a detector, it can provide a signal that there was exposure to above-the-threshold temperatures. Such a device can ensure that frozen food is handled correctly and is safe for consumption. As a sensor, it could be used by the workers in the supply chain, while as a detector, it could be useful for end consumers, ensuring that the food was properly frozen during the whole supply chain.