Capacitors out of recycled printed electronics paper substrates

The purpose of this project was to investigate the possibility of recycling conductive ink printed paper substrate previously used in printed electronics, and reworking it into a conductive paper. Such conductive substrate was further used as a conductive layer in capacitor construction. Firstly, paper printed with conductive carbonaceous ink was re-pulped. Substrate was torn into small pieces 2"x2". The goal of re-pulping was to make suspension of ink and paper fibers.

Secondly, paper handsheets were prepared with additional amounts of conductive material. The electrical conductivity of the prepared handsheet was determined and electrical properties recorded. Further, a dielectric solvent-based ink was formulated using vacuum metalized flake aluminum pigment (VMP) and vinyl based resin. Vacuum metallized flake provides smooth metallic finish. Flake itself was not covered with fatty acid as found on traditionally milled aluminum flakes. Dielectric ink formed larger area then conductive graphite ink that was deposited on the top of dielectric layer. Conductive ink was prepared using graphite with the Brunauer-Emmett-Teller (BET) surface area of >500 m²/g respectively. Graphite chosen for this experimental work has platelet morphology. The diameter of the selected platelets was 15-25 microns. The thickness of the platelets was in the range of 10-15 nm. � Ink was prepared using water-based formula. Binder for the ink was a commercially available acrylic based resin suitable for direct and indirect food contact applications. The prepared inks were applied onto the conductive paper substrate. Sheet resistance of conductive layers was measured via 4-point probe method. First down was dielectric aluminum based ink. Air-drying after printing was done in hot air oven at 120@C for 5 minutes. Functionality of prepared capacitor was tested via Precision LCR meter (Agilent E4980A). It was demonstrated that it is possible to reuse graphite printed substrates formerly used in printed electronics for building new conductive structures such as a capacitors.