These promising developments are detailed in an article co-authored by a researcher at the university.

Over the last decade, connected objects have become an important part of our daily lives for a variety of applications (leisure, surveillance, measuring vital health parameters, etc.) - this is the field of the Internet of Things (IoT). As soon as these objects are mobile (watches, drones, etc.), their autonomy is generally rapidly limited. Managing to supply them with sufficient energy is now a major challenge for research. This is also the case for even smaller communicating objects, which are about the size of a grain of rice. These miniature objects could be used for the local delivery of drugs to the human body, the monitoring of polluted areas that are inaccessible or the medical surveillance of patients.

In an article in the newspaper Energy & Environmental Sciencea teacher-researcher at the university (see box) and two colleagues from Nantes have produced a detailed review of the challenges of energy autonomy for the Internet of Miniature Objects. To ensure this autonomy, two complementary electrochemical energy storage devices are the focus of intense research by the various laboratories involved. The first is responsible for supplying continuous energy to the object. It is based on miniaturised lithium ion batteries.

The second, which is the focus of this article, is manufactured to respond to intense current peaks. These are very fast, millimetre-sized supercapacitors: micro-supercapacitors.sators. It's difficult to store a large amount of energy in such a small space. Increasing it significantly is the focus of current research. But nature offers a number of ways of improving performance. For example, to maximise the surface area for exchanging oxygen with the blood, our lungs contain hundreds of millions of alveoli in a 3D structure reminiscent of a tree. Similarly, in micro-supercapacitors, the use of the third dimension makes it possible to increase the surface area of interaction between their two main components (the electrode materials and the electrolyte ions) without altering the size of the object. By mimicking these biological structures, the performance of 3D micro-supercapacitors improves significantly, enabling them to store a quantity of energy never achieved by their 2D predecessors.

Scientific publications

Challenges and prospects of 3D micro-supercapacitors for powering the internet of thingsChristophe Lethien, Jean Le Bideau and Thierry Brousse, Energy Environ. Sci., 2018. In this review article, the authors discuss at length the technologies and topologies that make it possible to manufacture these micro-supercapacitors, as well as the technological hurdles currently holding back the industrial transfer of these technologies.