Racemic Amino Acid Piezoelectric Transducer.

Single crystal L-amino acids can exhibit technologically useful piezoelectric and nonlinear optical properties. Here we predict, using density functional theory, the piezoelectric charge and strain and voltage tensors of the racemic amino acid DL alanine, and use the modeling data to guide the first macroscopic and nanoscopic piezoelectric measurements on DL-alanine single crystals and polycrystalline aggregates. We demonstrate voltage generation of up to 0.8 V from DL-alanine crystal films under simple manual compression, twice as high as other amino acid crystals. Our results suggest that net molecular chirality is not a prerequisite for piezoelectric behavior in organic crystals. The transducer presented herein demonstrates that DL-alanine crystals can be used in applications such as temperature and force measurement in biosensors, data storage in flexible electronic devices, and mechanical actuation in energy harvesters.