Transfer printing of magnetic structures with enhanced performance using a new type of water-soluble sacrificial layer

Abstract

A transfer printing process is developed for thin film systems using a new type of water-soluble sacrificial layer – uncured polyvinylpyrrolidone (PVP). The bio-compatible PVP has a dual function, acting as both a buffer and a water-soluble sacrificial layer. Compared with the direct deposition of PyCu Giant Magneto-resistance (GMR) sensors onto bio-relevant, thermoplastic and flexible PEEK foils, the sensitivity of sensors transferred onto PEEK from a PVP-buffered Si substrate is raised from 4.1 T⁻¹ to 30.8 T⁻¹ and the GMR ratio is raised from 2% to 12%. This means that comparable values were achieved and sometimes even exceeded on Si substrates. The performance enhancement is proved to be the result of the decoupled arrangement of the substrate material and the tailored mechanical stress state. The transfer process developed is of a general nature and can be applied to other thin film systems and complete electronic components. The transferred sensors are used to count magnetically functionalised containers consisting of Fe-filled carbon nanotubes in a polymeric matrix. A detection rate ≥91% was achieved.