Novel Manufacturing Processes for Ultra-Low-Cost Paper-Based RFID Tags with Enhanced "Wireless Intelligence"

The objective of this study is to demonstrate ultra-low-cost paper substrates for the realization of inexpensive RFID tags that can be integrated with batteries and sensors for wireless sensing, tracking and monitoring applications. The first step toward achieving this goal is to demonstrate "conductors on paper substrates" from processing standpoint and to characterize the electrical performance of paper substrates up to 2 GHz form design standpoint. The conductors are achieved by (i) direct-write ink jet printing technology with tailored conductive ink and by (ii) conventional copper etching upon lamination of metal foils on to the paper substrates. There are several issues in optimizing the processes in either of the two approaches. For example, ink jet printing would require smooth surface finish, good adhesion, less smearing of the ink, fast curing profile, and ultimately copper-like conductivity of the printed ink and rapid prototyping for high volume manufacturing. On the other hand, metallization using copper will require bonding of copper onto paper surface, adhesion, compatibility with copper etch solutions and lithography, and moisture sealing. Both approaches have been successfully demonstrated for printing conductors on paper substrates which can be easily scaled to large-quantity manufacturing. For the electrical characterization of the paper substrates up to 2 GHz, one microstrip ring resonator was designed and fabricated for extracting dielectric constant and dielectric losses. The copper metallization of paper substrates and the dielectric characterization of paper up to 2 GHz are reported for the first time.