Researchers Identify Stability Range for Piezoelectric Glycine

Researchers have identified a specific size range that stabilizes the piezoelectric beta-phase of glycine. This phase converts mechanical pressure into electricity. The beta-phase of glycine is typically unstable, transforming into a non-piezoelectric alpha-phase. This instability has previously limited its use in electronic devices.

The team used electrohydrodynamic (EHD) spraying to create glycine nanocrystals. This technique uses electricity to pull a liquid solution into tiny droplets. This process allowed the creation of nanocrystals without a physical mold or template. This method enabled the study of the crystals in their pure form.

Experiments revealed that the piezoelectric beta-phase remains stable when the crystal radius is between five and 120 nanometers. Crystals smaller than five nanometers remained unstable clusters. Crystals larger than 130 nanometers quickly lost their piezoelectric properties. This finding provides a precise guide for maintaining the material's electricity-generating capabilities.

Advanced microscopy confirmed these findings. Individual nanocrystals within the five to 120 nanometer range showed a strong and consistent piezoelectric response. The electric field used during creation automatically aligned the internal dipoles of the crystals. This alignment means these materials could be used immediately in sensors or chargers without additional processing.

This research offers new insights into how molecular crystals grow in confined spaces. Defining this stability regime is a step toward using biological molecules in green electronics. These electronics would be safe for the human body. The team is now exploring how to integrate these stable nanocrystals into flexible films for medical sensors. The findings were published in the journal *Reports on Progress in Physics*.