Boosting the Piezoelectric Sensitivity of Amino Acid Crystals by Mechanical Annealing for the Engineering of Fully Degradable Force Sensors

Abstract

Biodegradable piezoelectric force sensors can be used as implantable medical devices for monitoring physiological pressures of impaired organs or providing essential stimuli for drug delivery and tissue regeneration without the need of additional invasive removal surgery or battery power. However, traditional piezoelectric materials, such as inorganic ceramics and organic polymers, show unsatisfactory degradability, and cytotoxicity. Amino acid crystals are biocompatible and exhibit outstanding piezoelectric properties, but their small crystal size makes it difficult to align the crystals for practical applications. Here, a mechanical-annealing strategy is reported for engineering all-organic biodegradable piezoelectric force sensors using natural amino acid crystals as piezoelectric materials. It is shown that the piezoelectric constant of the mechanical-annealed crystals can reach 12 times that of the single crystal powders. Moreover, mechanical annealing results in flat and smooth surfaces, thus improving the contact of the crystal films with the electrodes and leading to high output voltages of the devices. The packaged force sensors can be used to monitor dynamic motions, including muscle contraction and lung respiration, in vivo for 4 weeks and then gradually degrade without causing obvious inflammation or systemic toxicity. This work provides a way to engineer all-organic and biodegradable force sensors for potential clinical applications.

Piezoelectric dressings for advanced wound healing

“…After being encapsulated by polylactide (PLA), the piezoelectric voltage can be obviously output after implantation in animals. There are many studies on the preparation of the piezoelectric structure of amino acids, but most of the applications for the use of amino acid piezoelectric properties are in biosensors, 86,88–91 while there are relatively few in medical therapies. There are a few research studies focusing on the application of amino acids for wound treatment, but none of them use their piezoelectric properties.…”

Bioinspired Amino Acid Based Materials in Bionanotechnology: From Minimalistic Building Blocks and Assembly Mechanism to Applications

“…Choosing conductive polyaniline and polylactic acid to package mechanical-annealed Ile crystals, the prepared piezoelectric sensors generate an open circuit voltage of more than 0.4 V under an applied force of 100 N. In addition, due to its excellent biocompatibility and biodegradability, the packaged force sensors can be used to monitor muscle contraction and lung respiration in vivo and work steadily for up to 4 weeks. 211 Hydrogen bonds, as one of the main driving forces, play an essential role in producing amino acid based supramolecular self-assembly. 39 Ji et al reported a typical example of the hydrogen-bonded face-to-face dimers in L-Tyr crystals, which mediate the formation of tightly packed, rigid, low-symmetrical packing.…”

“…It is noteworthy that the piezoelectric constant of mechanical-annealed Ile crystals is 12 times that of its crystal powders (Figure b). Choosing conductive polyaniline and polylactic acid to package mechanical-annealed Ile crystals, the prepared piezoelectric sensors generate an open circuit voltage of more than 0.4 V under an applied force of 100 N. In addition, due to its excellent biocompatibility and biodegradability, the packaged force sensors can be used to monitor muscle contraction and lung respiration in vivo and work steadily for up to 4 weeks . Hydrogen bonds, as one of the main driving forces, play an essential role in producing amino acid based supramolecular self-assembly .…”

“…(b) Quasistatic piezoelectricity of different amino crystals (Ile, His, Leu, Thr, and Ser) without (− MA) and with (+ MA) mechanical annealing. Reprinted with permission under a Creative Commons CC BY License from ref . Copyright 2023 Wiley-VCH.…”

Self-Assembly of Metabolite Nanostructures toward Functional Biomaterials

“…Amino acids and peptides have been reported to obtain a variety of nanostructures, including nanofibers, nanotubes, nanowires, and nanosheets. However, their structures often show random orientations, which limits their bulk properties and potential applications. , For performance enhancements and new features, the fabrication of uniformly oriented structures is indispensable. − Various methods have been adopted to fabricate unidirectionally polarized structures.…”