New Horizons: Porous Piezoelectric Single Crystal Sensors

Piezoelectric materials generate an electrical charge in response to mechanical stress. These properties make them important materials for pressure sensors, medical transducers and vibration energy harvesters and the market is estimated to be £28 billion by 2025. Current commercial materials are based on dense ceramics since they generate a high charge in response to mechanical stress. However, they have a range of disadvantages.

(i) current materials are lead-based, such as lead zirconate titanate (PZT), and generate over 2500 tons of lead electronic waste per annum,
(ii) existing materials are high density and high stiffness, leading to poor impedance matching with biological tissue or water,
(iii) the high permittivity of dense materials leads to poor performance for sensing and harvesting since performance indicators are inversely proportional to permittivity,
(iv) ceramic elements can only be produced in limited geometries since they are made by pressing ceramic powders and subsequent high-temperature sintering.

POPSICALS will overcome the disadvantages of existing ceramics by developing a new manufacturing process based on a magnetic field enhanced freeze-casting process to create single crystal-like lead-free porous piezoelectric materials. This will combine the high piezoelectric charge coefficients of single-crystal materials with the low permittivity, low density and low stiffness of porous materials.