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Quantum tunnelling composite
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<p> Quantum tunnelling composites (QTCs) are <a href="/facts/Composite_material/UBysQldh">composite materials</a> of <a href="/facts/Metal/pqQVs8QU">metals</a> and non-<a href="/facts/Electrical_conductance/hxSt0UAj">conducting</a> <a href="/facts/Elastomer/kCSD0udN">elastomeric</a> binder, used as <a href="/facts/Pressure_sensor/ccQINerP">pressure sensors</a>. They use <a href="/facts/Quantum_tunnelling/WU4NMrKx">quantum tunnelling</a>: without <a href="/facts/Pressure/eyc37GRG">pressure</a>, the conductive elements are too far apart to conduct <a href="/facts/Electricity/hNC8D65W">electricity</a>; when pressure is applied, they move closer and <a href="/facts/Electron/L0KBo5cW">electrons</a> can tunnel through the <a href="/facts/Electrical_insulation/SfSXkrh5">insulator</a>. The effect is far more pronounced than would be expected from <a href="/facts/Classical_electrodynamics/vK0YI6dj">classical</a> (non-<a href="/facts/Quantum/4x5QTxGB">quantum</a>) effects alone, as classical <a href="/facts/Electrical_resistance/hxSt0UAj">electrical resistance</a> is <a href="/facts/Linear/fChtg3KC">linear</a> (proportional to distance), while quantum tunnelling is <a href="/facts/Exponential_function/ewlYxvR2">exponential</a> with decreasing distance, allowing the resistance to change by a factor of up to 1012 between pressured and unpressured states. </p><p>Quantum tunneling composites hold multiple designations in specialized literature, such as: conductive/semi-conductive polymer composite, <a href="/facts/Piezoresistive_effect/9zLp7Rt8">piezo-resistive</a> sensor and <a href="/facts/Force-sensing_resistor/DJ3BID2B">force-sensing resistor</a> (FSR). However, in some cases Force-sensing resistors may operate predominantly under <a href="/facts/Percolation/CRP2RCt6">percolation</a> regime; this implies that the composite resistance grows for an incremental applied <a href="/facts/Stress_(mechanics)/ErAXDbbd">stress</a> or force. </p>