Sublimation of Orientated Amino Acid Films with Reliable, Tunable, Single-Crystal Piezoelectric Performance

Biomolecular crystals have emerged as next-generation sustainable piezoelectric materials owing to their economical, biocompatibility, biodegradability, and energy-harvesting attributes versus commercially used ceramics. However, their natural self-assembly from saturated solutions results in non-uniform piezoelectric device layers with weak electromechanical output, both within individual samples and across multiple batches, which is limiting their acceleration into mainstream technological applications. Here, we report sublimation-driven crystallization as an effective fabrication technique yielding consistent and highly repeatable vertically aligned films of monoclinic amino acids crystallizing in the non-centrosymmetric monoclinic P21 space group (L-methionine [d33max = 6.57 ± 0.66 pC/N], L-leucine [d33max = 9.15 ± 0.09 pC/N], and L-valine [d33max = 9.61 ± 0.27 pC/N]) with reliable homogeneity in their piezoelectric performance. This solvent-free processing highlights a robust and standardized fabrication route for manipulating electromechanical properties across any number of amino acid piezoelectric device layers grown under identical conditions without relying on any post-processing methods.