| Summary: | In this work, we developed and fabricated a paper-based anisotropic magneto-resistive sensor using a sputtered permalloy (Ni<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>81</mn> </msub> </semantics> </math> </inline-formula>Fe<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>19</mn> </msub> </semantics> </math> </inline-formula>) 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 <inline-formula> <math display="inline"> <semantics> <msup> <mn>45</mn> <mo>∘</mo> </msup> </semantics> </math> </inline-formula> in the AMR response of the paper-based Ni<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>81</mn> </msub> </semantics> </math> </inline-formula>Fe<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>19</mn> </msub> </semantics> </math> </inline-formula> thin film compared to a Ni<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>81</mn> </msub> </semantics> </math> </inline-formula>Fe<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>19</mn> </msub> </semantics> </math> </inline-formula> 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 <inline-formula> <math display="inline"> <semantics> <msup> <mn>90</mn> <mo>∘</mo> </msup> </semantics> </math> </inline-formula>-anisotropy angle are explained through the superposition of the responses of Ni<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>81</mn> </msub> </semantics> </math> </inline-formula>Fe<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>19</mn> </msub> </semantics> </math> </inline-formula> inheriting the fibrous topography and smoother Ni<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>81</mn> </msub> </semantics> </math> </inline-formula>Fe<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>19</mn> </msub> </semantics> </math> </inline-formula> on buried fibrous topographies. As for the sensitivity and reproducibility of the sensor signal, we obtained a maximum AMR peak of <inline-formula> <math display="inline"> <semantics> <mrow> <mn>0.4</mn> <mo>%</mo> </mrow> </semantics> </math> </inline-formula>, min-max sensitivity range of <inline-formula> <math display="inline"> <semantics> <mrow> <mo>[</mo> <mn>0.17</mn> <mo>,</mo> <mn>0.26</mn> <mo>]</mo> <mo>%</mo> </mrow> </semantics> </math> </inline-formula>, average asymmetry of peak location of <inline-formula> <math display="inline"> <semantics> <mrow> <mn>2.7</mn> </mrow> </semantics> </math> </inline-formula> <inline-formula> <math display="inline"> <semantics> <mfrac> <mi>kA</mi> <mi mathvariant="normal">m</mi> </mfrac> </semantics> </math> </inline-formula> within two consecutive magnetic loading cycles, and a deviation of 250⁻850 <inline-formula> <math display="inline"> <semantics> <mfrac> <mi mathvariant="normal">A</mi> <mi mathvariant="normal">m</mi> </mfrac> </semantics> </math> </inline-formula> of peak location across several anisotropy angles at a base resistance of ∼100 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">Ω</mi> </semantics> </math> </inline-formula>. Last, we demonstrated the usability of the sensor in two educational application examples: a textbook clicker and interactive braille flashcards.
|
|---|