The ATHENA group recently published this paper in the April 2015 Flexible Electronics special edition of the Proceedings of the IEEE.
This paper is a review of a range of emerging technologies for radio frequency (RF) components and systems, whose unusual properties are acquired by virtue of the advantageous use of novel and (in the area of high frequency electronic) uncommon materials and manufacturing technologies.
Indeed, the additive manufacturing technologies (AMT) presented in the paper have tremendous advantages, with regard to environmental friendliness, low cost, as well as rapid fabrication turnaround. However, their most valuable assets are their compatibility with, virtually, any substrate materials (notably flexible ones), and their material deposition versatility. A more detailed description of one of these technologies—inkjet-printing—can be found in this blog post.
Using these AMTs, planar high-frequency-compatible flexible components—such as lumped components (inductors, capacitors, resistors), vias, metamaterial structures, as well as antennas— can be fabricated. Furthermore, the use of printable semiconducting materials inks (such as graphene, carbon nanotubes, and conductive polymers) allows for the low cost fabrication of a wide range of high performance sensors for gas, temperature, and strain measurement and detection.
Likewise, entire flexible systems—solar-powered RF beacons, ground penetrating radars, RFID front-ends—are also manufacture-able by combining AMT-fabricated passive components and traces with standard integrated circuit chips (ICs), to create what are usually referred to as “Flexible Hybrid Electronic” systems.
As an evolution of foldable paper-based “origami” RF devices, a more recent, and key, innovation enabled by the use of multi-material AMTs is the fabrication of physically reconfigurable 3D components and systems—also called 4D components, where the 4th dimension is that of the configuration space of the device.