Future smart pills are being developed to monitor health conditions from inside the body and dissolve safely after completing their task. Now, a breakthrough in edible electronics in the form of a toothpaste-based transistor could become a key component of these smart pills.

Many commercial toothpaste products contain crystals of copper phthalocyanine, a blue pigment used as a whitening agent. This pigment adheres to teeth, functioning as an optical filter to enhance their whiteness, and is gradually ingested throughout the day as it is removed by saliva. Researchers at the IIT-Italian Institute of Technology (Milan, Italy) studied the properties of copper phthalocyanine and, through lab simulations and analysis of existing clinical data, determined that on average, people ingest about 1 milligram of this substance every time they brush their teeth. With the amount ingested daily, it is theoretically possible to create around 10,000 edible transistors.

What makes copper phthalocyanine particularly interesting is its chemical structure, which supports charge conduction within its crystals, making it an ideal candidate for use as a semiconductor in organic electronics. The research team incorporated this pigment as a semiconductor into an existing formula for building edible circuits. These circuits are constructed on an ethylcellulose substrate, with electrical contacts printed using inkjet technology and a gold particle solution, commonly used in culinary decoration. A "gate" made from an electrolytic gel based on chitosan, a food-grade gelling agent derived from crustaceans like blue crabs, allows the transistor to function at a low voltage of less than 1V, according to the findings published in Advanced Science.

The next goal for the research team is to identify additional edible materials with suitable chemical and physical properties to create intelligent, ingestible electronic devices that could be used in healthcare applications, such as monitoring internal body parameters within the gastrointestinal tract. 

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