Variable capacity polymer based energy harvesters with integrated macroporous elastomer springs

We introduce a manufacturing concept of variable capacity energy harvesters consisting of macroporous springs integrated within a conducting silicone rubber and dielectric. Printing and polymerising emulsion templates resulted in macroporous spring elements, which were coated with conducting silicone rubber to maintain the active contact surface. By increasing size and number of these springs, the capacitance change of the energy harvesters during compression and recovery increased from 0.4 nF/cm2 to 0.8 nF/cm2. During cyclic loading with 30 N at 2 Hz, the energy harvesters with macroporous springs delivered a power density of 0.58 µW/cm2 at a bias voltage of 50 V, which was 25 times higher than the control without springs. The energy harvesters provided a constant power output over three hours of cyclic loading (21,600 cycles), indicating their structural stability and the durability of the macroporous springs.