Improving the electrical conductivity by forming Ni powder chains in a shape-memory polymer filled with carbon black

We demonstrate a simple approach to significantly reduce the electrical resistivity of thermo-responsive shape-memory polymers (SMPs), so that they can be easily triggered for shape recovery by Joule heating at a low electrical voltage. After adding a small amount of Ni micro particles into a polyurethane SMP filled with carbon black (CB), the electrical resistivity is slightly reduced. However, if these Ni particles are aligned into chains (by applying a low magnetic field on SMP/CB/Ni solution and then drying to fix the conductive chains), the drop of electrical resistivity is significant. This kind of SNIP composites is suitable for cyclic operation as only micro/nano particles are used. A sample (40x15x1mm) with 10vol% of CB and 0.5vol% of chained Ni can be heated to 80 degrees C for shape recovery at 30 V (1.2 W) of power. This approach is generic and applicable for producing other conductive polymers.