Figure 1: GMR multilayers on ultrathin PET.
(a) Diagram of an imperceptible magnetic sensor foil. Cross-section of the GMR layer system (inset). (b) Free-standing array of five Co/Cu multilayer elements on 1.4-μm-thick PET foil. (c) Ultralight (3 g m−2) sensor array floating on a soap bubble and (d) crumpled between fingertips. Scale bars, 10 mm. (e) GMR characteristics of one Co/Cu first maximum element as prepared (green curve, R=16.9 Ω), after attaching to the palm and folding (blue curve, R=17.0 Ω), and after crumpling as shown in d (red curve, R=17.9 Ω). Comparison with a reference sample on rigid silicon (dashed grey curve, R=16.2 Ω). Corresponding measurements on the other elements in the array gave similar results. (f,g,h) Imperceptible GMR sensor array on a human palm with one element connected to a readout circuit during rest, moving the hand and in proximity to a permanent magnet. Scale bars, 20 mm. (i) Recorded resistance of the sensor element for f through h and Supplementary Movie 3. (j,k,l) On-skin magnetic proximity sensor using a Co/Cu second maximum GMR element on the fingertip connected to a linear array of light-emitting diodes (LEDs) (dashed red frame) as touchless interface. Scale bars, 10 mm (see Supplementary Movie 4).
