Novel Inkjet-printed Ferromagnetic-based Solutions for Miniaturized Wireless Power Transfer (WPT) Inductors and Antennas #Hoseon Lee 1 , Manos. M. Tentzeris 1 , Yoshihiro Kawahara 2 , Apostolos Georgiadis 3 1 Electrical and Computer Engineering, Georgia Institute of Technology Atlanta, GA, U.S.A, hoseon@ece.gatech.edu 2 Information and Communication Engineering, University of Tokyo Tokyo, Japan, kawahara@akg.t.u-tokyo.ac.jp 3 Centre Tecnologic de Telecomunicacions de Catalunya 08860 Castelldefels, Spain, ageorgiadis@cttc.es 1. Introduction Inkjet printing technology is emerging as a popular alternative to traditional circuit board fabrication techniques such as chemical etching and milling, finding increased application in the electronics and sensors industries [1]. Some of the striking properties who have contributed towards its widespread application are: a) it can provide a printing resolution down to a minimum of approximately 50 um, which makes it suitable for circuits in the microwave [2], and millimetre wave frequency range [3], b) it does not require a clean room or use of corrosive solvents, which in turn simplifies the necessity for specialized waste treatment, c) it is easily applied to very thin and flexible substrates such as paper, PET and textiles, d) it permits large volume circuit production. The capability for large volume production and use of low cost flexible substrate materials such as textiles, PET and paper have led to a natural application of inkjet printing in radio frequency identification (RFID) [2]. Various implementations of flexible passive microwave circuit components such as inductors, transformers and antennas have appeared in the literature [2]. The possibility of inkjet printing of complete System-On-Substrate, based on multilayer flexible substrate modules and inkjet deposition of active devices remains a challenge especially when it comes to operating at microwave frequencies, however important steps are taken towards this direction by applying inkjet printing of semiconducting polymers to develop organic thin film transistors (OTFTs) [4]. Furthermore, integration of off-the-shelf electronic components onto flexible substrates, and development of active circuits and wireless transceivers utilizing inkjet printing to develop passive interconnects, transmission lines and antennas has been successfully demonstrated [1][2][5]. A further challenge towards enabling complete system integration consists of inkjet printing of thin film energy storage elements such as capacitors and batteries [6]. Extending the operational autonomy of wireless sensors and transceivers has spurred significant efforts related to energy harvesting technologies, as well as wireless power transmission [7]. Towards this goal the integration of active circuits on flexible substrates such as PET and inkjet printing on paper, autonomously powered by amorphous silicon a-Si solar cells [8] or piezoelectric transducers [9], has also been recently demonstrated. Finally, the capability of inkjet deposition of carbon nanotubes has additionally opened the way to gas sensing applications, and furthermore towards the development of RFID systems with sensing capability [1]. A further challenge towards efficient System-On-Package integration is component miniaturization. Antennas and inductors typically require a large substrate area in order to achieve the necessary gain and inductance values respectively. Utilization of high permittivity or high permeability substrate materials permits size reduction and low profile implementation. This work focuses on the development of inkjet-printed ferromagnetic thin films based on cobalt nanoparticles, which are subsequently applied in the design of low profile inductors printed on paper substrate. Ferromagnetic thin films combine a high permeability with a high permittivity which allows for a further size reduction of the inductor components [10]. The paper provides nano-ink synthesis and 1A3-4 Proceedings of ISAP2012, Nagoya, Japan 14