The LEAF Project
At the heart of the LEAF innovation is an ultrathin foil, just a few micrometers thick, that integrates energy harvesting, energy storage, and dynamic 3D reshaping capabilities. The foil is fabricated using advanced inkjet and high-precision capillary printing (HPCAP) techniques, which allow for high-resolution control over the printed structures. The device is constructed on a temporary carrier and incorporates a sacrificial adhesion layer made from a proprietary lanthanum acrylic acid coordination polymer. On top of this lies a bilayer system consisting of a hydrogel (based on polyethylene-alt-maleic anhydride) and a stiffening polyimide layer, also developed through LEAF’s in-house technology.
This unique bilayer configuration enables the foil to undergo controlled 3D reshaping into compact, Swiss-roll-like structures with diameters of only a few hundred micrometers. The transformation occurs through selective etching of the sacrificial layer followed by hydrogel swelling in a water-based solution. This reshaping not only increases mechanical stability but also allows the device to conform to various surfaces and applications while maintaining full functional integrity.
A key innovation in LEAF is its integration of self-powering functionality. This is achieved through bi-functional materials deposited in interdigitated micro-electrode structures on the foil. These materials serve dual roles as both light harvesters and energy storage mediums. When exposed to light, they convert it into electrical energy and store it within an embedded microscale supercapacitor—effectively creating a “photo-storage” unit. This microsupercapacitor powers an integrated silicon chip, such as a radio-frequency integrated circuit (RFIC), enabling truly autonomous operation of the sensor node.
The foil’s 2D configuration maximizes surface area for the interdigitated electrodes, ensuring efficient light absorption and energy conversion. Despite its minimal thickness—approximately 5 micrometers—the device maintains an optimal weight-to-functionality ratio (R ≈ 0.95), and its structural integrity is preserved even after reshaping. This ensures the device continues to function reliably after deployment onto various application surfaces, such as curved or flexible substrates.
LEAF’s innovation lies in seamlessly combining advanced materials science, microscale energy systems, and flexible electronics into a single, manufacturable solution. The use of HPCAP printing allows for precise, reproducible fabrication of diverse functional materials, paving the way for scalable production. This enables the deployment of maintenance-free, adaptable, and energy-autonomous wireless motes across fields such as environmental monitoring, smart packaging, healthcare, and the Internet of Things.
In summary, the LEAF project represents a significant leap forward in the development of next-generation sensor systems. By integrating energy harvesting, storage, and 3D reshaping into a single, thin platform, it lays the foundation for a new era of self-sustaining, intelligent, and flexible electronic devices.