Comparison of miniaturized mechanical and osmotic energy harvesting systems

IoT stands for Internet of Things. It refers to the network of physical objects or "things" embedded with sensors, softwares, and other technologies that enable them to connect and exchange data with other devices and systems over the internet. The IoT has the potential to transform many areas of our lives, including home automation, healthcare, transportation, manufacturing, etc. By collecting and analyzing data from connected devices, businesses and organizations can gain insights that can help them make better decisions, improve efficiency, and reduce costs. Naturally, IoT requires energy to work and many techniques have been developed to limit the power consumption of the devices. These objects now need very little power to work, of the order of the mW or the mu W. However, the IoT devices need to run for long periods of time without being replaced or recharged. This is especially important for devices deployed in remote or hard-to-reach locations. In this framework, it is of great importance to develop energy harvesting systems for IoT. It is of prime importance to use energy from their environment rather than relying on conventional power sources like batteries or mains electricity. By reducing the need for disposable batteries, energy harvesting can help to reduce waste and minimize the environmental impact of IoT devices. Energy can be found in ambient light, temperature differences, vibrations, or electromagnetic radiation. In this review article we will focus on the recovery of energy from mechanical vibrations and on the recovery of mixing energy: these methods have in common to be based on material surface charges. We will detail different modes of operation: the realization of sensors that do not need power, the realization of energy recovery generators which store energy for sensor consumption, and finally the realization of energy recovery generators feeding directly sensors. We will describe the different physical mechanisms of these processes. We will then illustrate them with examples of outstanding achievements.