Imagine tiny piezoelectric force sensors that can be placed inside the body: they monitor physiological pressure changes in damaged organs, aid precise drug delivery, or promote tissue repair and regeneration. The best part? They require no battery power, and after use, the body absorbs and degrades them, eliminating the need for invasive removal surgery! However, traditional piezoelectric materials like inorganic ceramics and organic polymers suffer from inadequate degradability and cytotoxicity. Scientists identified amino acid crystals as a promising candidate – they are biocompatible and exhibit excellent piezoelectric properties. The challenge? These crystals are too small, like scattered sand, making it extremely difficult to align them into functional devices. Researchers Yi Cao and Bin Xue from Nanjing University found a solution: a special technique called "Mechanical Annealing". Using natural amino acid crystals as the piezoelectric material, they engineered fully organic, biodegradable piezoelectric force sensors. When treated with mechanical annealing, the crystals' power generation capability skyrocketed – achieving a piezoelectric coefficient 12 times higher than that of single-crystal powders! Furthermore, the treated crystal films became smooth and flat, like a phone screen protector, significantly improving contact with the electrodes and enabling stronger, more stable electrical signals. The resulting "absorbable piezoelectric force sensors", once packaged, were implanted in vivo and successfully monitored dynamic movements like muscle contractions and lung respiration continuously for 4 weeks. Afterwards, they gradually degraded without causing inflammation or systemic toxicity. This breakthrough offers new hope for future medicine, providing a pathway to design and manufacture fully organic, biodegradable force sensors for potential clinical applications! Fabrication of the Packaged Force Sensor: Preparation of Mechanically Annealed Crystal Films: Isoleucine was dissolved in deionized water to form a solution, heated, then transferred to an ice-water bath to stand, allowing crystal nuclei to form. The crystals were then collected and dried in an oven. The prepared isoleucine crystals were filled into a tablet mold and subjected to the mechanical annealing process, resulting in round, film-like crystals. Other amino acid crystals and their mechanically annealed counterparts were prepared using the same method. PLA-PAN Electrode Preparation: Polylactic acid (PLA) was dissolved in dichloromethane (DCM) to form PLA films, serving as the sensor's outer "protective membrane". But a membrane alone isn't enough; sensors need electrodes to collect weak electrical signals. The researchers had a clever trick: they immersed one side of the PLA film in a "reactive solution" (containing sulfuric acid and aniline). After processing, the originally insulating PLA film surface became coated with a conductive layer of polyaniline (PAN...
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