Molecular Engineering of Amino Acid Crystals with Enhanced Piezoelectric Performance for Biodegradable Sensors

Amino acid crystals have emerged as promising piezoelectric materials for biodegradable and biocompatible sensors; however, their relatively low piezoelectric coefficients constrain practical applications. Here, we introduce a fluoro‐substitution strategy to overcome this limitation and enhance the piezoelectric performance of amino acid crystals. Specifically, we substituted hydrogen atoms on the aromatic rings of L‐tryptophan, L‐phenylalanine, and N‐Cbz‐L‐phenylalanine with fluorine, resulting in significantly elevated piezoelectric coefficients. Density functional theory calculations further indicate that fluorination strengthens polarization by modifying molecular dipole moments. Consequently, these fluoro‐substituted crystals achieve piezoelectric coefficients of up to 50.36 pm/V, surpassing those of other organic piezoelectric materials such as polyvinylidene fluoride (PVDF), poly(l‐lactic acid) (PLLA), and gelatin. When integrated into flexible, biodegradable force sensors, the fluoro‐substituted crystals exhibit a broad sensing range, high sensitivity, and stable in vivo operation over extended periods. This work establishes a versatile route for boosting piezoelectricity in biomaterials, thereby broadening their scope in biomedical applications.