Billions of piezoelectric sensors are produced every year, improving the efficiency of many current and emerging technologies. By interconverting electrical and mechanical energy they enable medical device, infrastructure, automotive and aerospace industries, but with a huge environmental cost. Amino acids are the most basic biological components, and they are cheap and simple to crystallize , with significant piezoelectricity in single crystal and polycrystal forms . However, this response is highly anisotropic, and precise, orientated control over crystallisation is required to maximize the piezoelectric output of a crystalline amino acid device for development into a cohesive ceramic-type element. Our research is taking on the challenge of developing biomolecular crystals as organic, low-cost, high-performance sensors, to out-perform and phase-out inorganic device components with dramatically reduced environmental impact. In this talk I will discuss our methodologies for the design, growth, and engineering of these novel piezoelectric materials under three pillars:
• An ambitious computational workflow to enable the design of super-piezoelectric crystalline assemblies by combining high-throughput quantum mechanical calculations with machine learning algorithms;
• A new method of growing polycrystalline biomolecules, allowing for easy, efficient creation of macroscopic piezoelectric structures;
• Establishing effective electromechanical testing procedures to characterise fully insulated and contacted biomolecular device components.
Even 'weak' organic piezoelectric with modest piezoelectric constants can yield significant voltages in response to strain because the piezoelectric voltages produced under an applied force are inversely proportional to the material's dielectric constant

Sodium potassium niobate (K1-x-zNaxLiz)Nb1-yTayO3 (KNNLT) based piezoceramics are promising candidates as lead-free alternatives to Pb(Zr1-xTix)O3 (PZT) materials and are considered potentially suitable material for multilayer actuators (MLAs). The price advantage of base metal electrodes makes them attractive for the production of MLAs. However, they require firing under reducing conditions. Mastering the cofiring process to produce defect-free piezoelectric components is an important step towards the fabrication of competitive MLAs. We report an experimental study to develop a sintering procedure of KNNLT multilayer actuators at low pO2 to enable co-firing with Ni electrodes. Powder with composition (Na0.52K0.44Li0.04)Nb0.8Ta0.2O3 was synthesized via the mixed oxide route. For multilayer actuators, a combination of thermal analysis and sintering experiments allowed to derive processing conditions for binder removal. For sintering experiments, bulk samples as well as multilayer laminates were used. We investigated the phase composition, microstructure and electromechanical properties of bulk samples and multilayers, sintered under low oxygen partial pressure in the range of 10-10 atm to 10-12 atm at sintering temperatures of 950°C to 1000°C and after reoxidation at 850°C under pO2 = 10-6 atm for various dwell times. We demonstrate the impact of the sintering protocol, i.e., sintering temperature Ts and oxygen partial pressure pO2 on the actuator performance. Through optimizing the firing parameters, a multilayer was obtained, which exhibits a unipolar strain of 0.74 ‰ at 3 kV mm-1, a normalized strain coefficient d_33^* = 247 pm V-1 and a loss of tanδ = 0.041.

Enhancement of ferroelectric performance is known to be possible in the vicinity of a morphotropic phase boundary (MPB). A shift between tetragonal to orthorhombic/pseudotetragonal symmetry within a Tetragonal Tungsten Bronze (TTB) system can give rise to such an MPB. In this study, we investigate the solid solution between orthorhombic Ba4Na2Nb10O30 (BNN) and tetragonal Ba4Li2Nb10O30 (BLN) TTBs. Ceramics of composition Ba4(LixNa1-x)2Nb5O30 (xBLNN, x = 0.00, 0.10, 0.20, 0.30, 0.35, 0.40, 0.60, 0.70, 0.80, 0.90 and 1.00) was achieved through a two-step solid state synthesis route. The crystal structures were elucidated by powder X-ray diffraction, which suggest that a transition from orthorhombic (Ama2) to tetragonal (P4bm) symmetry occurs for a composition with x between 0.3 and 0.35, making the system eligible for an MPB. A second phase, with tungsten bronze-related structure, was identified, and observed to increase with increasing Li-content, for compositions of x > 0.70. The crystallographic site occupation of the Li-, Na- and Ba-ions in the TTB-structure, across the compositional range, was studied through Rietveld refinement of the diffraction data complemented by DFT calculations and is discussed with respect to lattice parameter size and stability of the TTB phase.