The invisible electronic chip that restores the sense of touch

It could soon be possible to restore tactile sensations for people fitted with prosthetics thanks to the Flexeo project. This research program, led by Mines Saint-Etienne, has entered the second phase after four years of development. Under the supervision of Sylvain Blayac, the team has designed a flexible electronic chip that can detect and reproduce tactile sensations.

In brief:

The goal of the Flexeo project is to restore tactile sensations for people who are deprived of them, thanks to an electronic chip.
The benefits of Flexeo go beyond the field of health, to augmented perception and environmental monitoring.

Tags:

# Centre of microelectronics in Provence

# Marc Ramuz

# Mines Saint-Etienne

# Roger Delattre

# Sylvain Blayac

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Restoring tactile sensations for people who are deprived of them will soon be more than just science fiction. This is one of the goals of the Flexeo research project, led by Sylvain Blayac, with support from Roger Delattre and Marc Ramuz, research professors at the Centre Microélectronique de Provence at Mines Saint-Etienne. Flexeo will enter the second phase in November 2024, extending the project for another four years thanks to funding from the Provence Alpes Côtes d’Azur region. The project was first launched in 2020 thanks to financing from the Plan Nano 2022, as part of the Important Project of Common European Interest (IPCEI) scheme. Around 15 people have made some form of contribution to this project.

4 years, 7 scientific papers and 6 theses later, Sylvain Blayac is presenting a miniature, flexible electronic chip built into a bendable, thin and stretchable medium. A device with so many potential applications.

Electronic skin to restore tactile sensations

The electronic chip turns into electronic skin when it is attached to a glove and connected on one side to an optical sensor that detects tactile perception, and on the other to vibrating motors providing haptic feedback. It was designed to restore and heighten tactile sensations, particularly for people fitted with prosthetics.

The sensor was jointly developed as part of the ANR Optiskin project, led by Marc Ramuz. Placed at the end of the finger, it can read any mechanical functions such as pressure or contact. It is based on a waveguide which is an optical sensor that sends a beam of light through a material that reacts to pressure. When the pressure changes, this material deforms and therefore modifies the way in which the light passes through or is reflected. A detector senses these changes and transforms them into a signal, processed through the card. The card interprets the incoming information to determine the applied pressure and sends it to the electrodes on the forearm.

Body channel coupling technology then takes over, using the human body as a channel to emit signals and this activates the vibrating motors that are placed on the body. These motors generate tactile sensations on the skin. In providing this haptic feedback, the device restores a form of sensitivity for the user and allows them to adjust the pressure they apply to the prosthetic when holding a delicate object such as an egg or a glass, for example.

From a rigid medium to a flexible multi-application chip

Before getting to this stage, the team began by designing the architecture for the chip on a rigid medium. During this first step, the Ocass platform was developed, with a built-in processor core by STMicroelectronics, a project partner. “This step was crucial to be able to then easily build prototypes of the applications”, specifies Sylvain Blayac. “The aim of this platform is twofold, firstly research-based with the development of the electronic skin, and also educational”. Every year, around a hundred students from the center are trained thanks to this platform.

The next step was to transfer this technology over to a flexible and stretchable biocompatible polymer. To link all the various components – motherboard, communication card, sensor card, and energy source – the team developed capacitive coupling technology. “It’s like a post-it, in that it can be attached and removed!” jokes the researcher. Above-all, this means the chip can easily be adapted to different uses, by simply connecting different modules.

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La puce électronique flexible Flexeo, fixée à un gant.

Gallery:

The Flexeo chip attached to a glove. The Ocass platform in the foreground.

The Flexeo electronic chip on the biopolymer medium.

Diagram of the Flexeo components

Diagram of the device attached to the glove.

The next challenge is the energy supply. Given that this is a wearable device, the system cannot be plugged in to a power outlet. The team opted for the development of flexible lithium-ion batteries and this activity is led by Thierry Djenizian. To make sure they are adapted to the device being worn almost continuously, these batteries are designed to charge in a flash. In just 10 seconds, they will be charged for an entire day.

Other application areas

The outcome of these developments: “An ecosystem of electronic objects, in which an information processor core, different types of sensors and an output communication module are placed, which can then trigger movements”, summarizes Sylvain Blayac

Another goal for the project is the concept of ‘augmented perception’. In integrating different sorts of sensors, such as electromagnetic field sensors, physical sensations can be triggered in the event of danger, therefore providing proactive prevention. One of the applications envisaged following discussions with the French Aerospace Lab (ONERA) is to provide a physical sensation of ground proximity for helicopter pilots in the event of reduced visibility.

4 years for an even more accurate reproduction of touch

However, reproducing a lifelike electronic version of tactile perception is no easy task. The human sense of touch takes into account a great number of mechanical parameters such as shear and average pressure, to then send the brain a comprehensive overview of the object touched, including its shape, weight, texture or dynamics if the object moves, for example. For the moment, the first prototype only includes a sensor that is concentrated on one single mechanical feature. One of the goals of the second phase of the project is to improve the demonstrator by adding multi-parameter sensors, to better mimic the mechanical behaviors of skin.

The haptic feedback also needs to be optimized. “The body is not very good at quantifying a sensation, such as the one produced by the motors in the current prototype, but it perceives the variations very well”, specifies Sylvain Blayac. “For this second phase, we are going to broaden our research to cover these issues of effective perception”. To do so, the team will be working in partnership with perception specialists.

The lightweight and compact nature of the electronic skin, as well as its low energy consumption, make it feasible for other potential uses, beyond the field of healthcare. The Flexeo project team is now working on using these chips to develop autonomous communicating objects. It might soon be possible for example to leave wind-powered sensors for assessing air quality in place on a continuous basis, to take measurements in an urban environment.