A “toothpaste-based” transistor to make electronics edible, the IIT project: how it works

October 15, 2024

A edible transistor based on pigments present in toothpaste to monitor the state of health of the human body from the inside: this is the idea behind the creation of a group of researchers from the Italian Institute of Technology (IIT) in Milan led by Elena Feltriwho created a transistor from copper phthalocyanine, used as a whitener in toothpaste. A potentially revolutionary idea, which opens up new frontiers in the field of biomedical engineering and organic electronics. We may in fact be at the dawn of the era of smart pillsdesigned to monitor organs closely and then safely dissolve after serving their purpose. However, to understand how it works, it is necessary to take a step back.

The key to the IIT project lies in copper phthalocyanine. It is a blue pigment used as whitening agent in toothpastes. Through studies conducted in collaboration with dental experts from the University of Novi Sad in Serbia, the team of researchers discovered that humans ingest on average about 1 milligram of this compound every time they brush their teeth.

“With the amount of copper phthalocyanine we ingest every day, we could theoretically produce around 10,000 edible transistors,” comments Elena Feltri, PhD student at the IIT’s CNST. The chemical structure of copper phthalocyanine allows for a effective conduction of electric chargemaking it perfect for electronic applications.

This explains the logic with which the team integrated small quantities of this pigment within a structure already tested for edible circuits. In this way, devices were built on an ethyl cellulose substrate, using inkjet technology to print electrical contacts with gold particles (essential for the transmission of electrical contacts).

All this is made possible by the “gate”, i.e. the component that controls if and how the current flow circulates within the transistor. In this specific case it is made with an electrolyte gel based on chitosana gelling agent derived from shellfish. This allows the device to operate at voltages below 1 V, making it suitable for healthcare and food applications.

The research team’s next step will be to identify others edible substances which can have the right chemical-physical characteristics useful for creating an intelligent and edible electronic device, to be used in the healthcare sector, such as monitoring the body parameters of the gastrointestinal tract.

The ultimate goal is therefore to create edible electronic devices that can be used in health monitoring, but also in quality control in the food industry. The latter is an extremely topical aspect given the increase in pathologies in the Western world linked to the processing of industrially derived foods.

The transistorwhose name derives from the portmanteau of the English words transconductance And varistoris an electronic component made with semiconductor materials such as silicon and germanium. Three terminals used to connect the device to the external circuit are connected to the body of the transistor: by applying an electrical voltage to two of the terminals it is possible to regulate the flow of electrons that passes through the transistor itself, thus being able to amplify the input signal (i.e. to ensure that the output voltage or electrical current is higher than the input one).

That’s why the transistor it finds use within an electrical circuit as an amplifier or as a switch and has become the basis of any electronic device. In the first case, by exploiting the physical properties of semiconductor materials, it can transform the input current (or voltage) into a signal with greater power. A practical example is given by hearing aids for people with hearing impairments. These devices, in fact, are equipped with a very small microphone capable of picking up nearby sounds and, thanks to a transistor, amplifying the volume directly inside the person’s ear.

In the second case, however, the device can amplify the input signal or cancel it. As a switch, the transistor allows or prevents the transit of current within the electrical circuit: the system can therefore assume the binary value of “0” or “1”, allowing the creation of digital electronic circuits at the basis of Boolean logic. In this capacity it is used in the IT field: each microchip (processor or memory) is made up of billions of transistors which allow data to be stored or instructions and instructions to be executed. algorithms of various computer software.

Alexander Marchall

Alexander Marchall is a distinguished journalist with over 15 years of experience in the realm of international media. A graduate of the Columbia School of Journalism, Alex has a fervent passion for global affairs and geopolitics. Prior to founding The Journal, he contributed his expertise to several leading publications.