Abstract
In this work, we developed and fabricated a paper-based anisotropic magneto-resistive sensor using a sputtered permalloy (NiFe) 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 in the AMR response of the paper-based NiFe thin film compared to a NiFe 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 -anisotropy angle are explained through the superposition of the responses of NiFe inheriting the fibrous topography and smoother NiFe on buried fibrous topographies. As for the sensitivity and reproducibility of the sensor signal, we obtained a maximum AMR peak of , min-max sensitivity range of , average asymmetry of peak location of within two consecutive magnetic loading cycles, and a deviation of 250–850 of peak location across several anisotropy angles at a base resistance of ∼100 . Last, we demonstrated the usability of the sensor in two educational application examples: a textbook clicker and interactive braille flashcards.
Highlights
In this paper, motivated by the aforementioned observation, we address the magneto-resistive properties of paper-based thin films of Ni81 Fe19 and the feasibility of a paper-based sensor using the principle of anisotropic magneto-resistance (AMR)
We found that films of 900 nm thickness exhibited the least magnetic coercivity, which we verified in this work to lead to a better AMR sensitivity
We developed a paper-based AMR sensor that can be used, for instance, in educational applications
Summary
The mathematics of origami and kirigami, contemporized with laser cutting ([5,6]), enable non-planar paper products such as pop-ables [7], foldable circuit boards [8] and three-dimensional actuators ([9,10]). Actuation of three-dimensional paper structures was enabled by employing magnetism as an added value to the light weight and mechanical bendability of paper, e.g., by embedding magnetic ferrites during or after papermaking ([11,12]) or by depositing thick layers of organic resins filled with magnetic particles ([13,14]). In our previous work ([15,16]), we considered the magnetic properties of non-patterned, thin films of permalloy
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