Paper-Based Magneto-Resistive Sensor : Modeling, Fabrication, Characterization, and Application
In this work, we developed and fabricated a paper-based anisotropic magneto-resistive sensor using a sputtered permalloy (Ni 81 Fe 19 ) thin film. To interpret the characteristics of the sensor, we proposed a computational model to capture the influence of the stochastic fiber network of the paper surface and to explain the physics behind the empirically observed difference in paper-based anisotropic magneto-resistance (AMR). Using the model, we verified two main empirical observations: (1) The stochastic fiber network of the paper substrate induces a shift of 45 ∘ in the AMR response of the paper-based Ni 81 Fe 19 thin film compared to a Ni 81 Fe 19 film on a smooth surface as long as the fibrous topography has not become buried. (2) The ratio of magnitudes of AMR peaks at different anisotropy angles and the inverted AMR peak at the 90 ∘ -anisotropy angle are explained through the superposition of the responses of Ni 81 Fe 19 inheriting the fibrous topography and smoother Ni 81 Fe 19 on buried fibrous topographies. As for the sensitivity and reproducibility of the sensor signal, we obtained a maximum AMR peak of 0 . 4 % , min-max sensitivity range of [ 0 . 17 , 0 . 26 ] % , average asymmetry of peak location of 2 . 7 kA m within two consecutive magnetic loading cycles, and a deviation of 250⁻850 A m of peak location across several anisotropy angles at a base resistance of ∼100 Ω . Last, we demonstrated the usability of the sensor in two educational application examples: a textbook clicker and interactive braille flashcards.