(Nanowerk Spotlight) Medical devices that interface with the human body need power sources as safe as they are reliable. While sophisticated electronics can monitor health conditions and deliver treatments, powering these devices without risking tissue damage or immune responses remains a fundamental challenge.
Materials that generate electricity from mechanical force, known as piezoelectric materials, could potentially harvest energy from natural body movements. However, existing options present difficult tradeoffs. Ceramic-based materials produce strong electrical outputs but contain toxic elements. Biocompatible polymers suffer from inconsistent performance due to their irregular internal structure. Natural biological materials, while perfectly safe, generate electrical signals too weak for most practical applications.
A research team at Chongqing University has identified an unexpected solution in vitamin molecules. Their study in Advanced Materials (“Piezoelectric Vitamin-Based Self-Assemblies for Energy Generation”) demonstrates that vitamins can self-assemble into crystals capable of generating significant electrical charge when compressed. These structures combine biological safety with electrical performance that approaches some inorganic piezoelectric materials.
The researchers conducted a systematic investigation of vitamin crystal formation. Out of 31 vitamin compounds tested, 20 successfully formed high-quality crystals through controlled temperature and evaporation processes. X-ray analysis revealed three primary patterns of molecular organization: face-to-face stacking where molecules align directly atop each other, staggered arrangements with offset molecules, and antiparallel configurations where molecules alternate directions.
Using density functional theory calculations supported by experimental validation, the team analyzed how these different crystal structures influenced electrical generation. Vitamin B7 (D-biotin) emerged as particularly effective, producing 42.8 picocoulombs of charge per Newton of applied force. This piezoelectric response is comparable to some inorganic materials, such as BiB3O6 (40 pC N-1), but remains below the highest-performing ceramics.
Natural sources and biological functions (PDB entry 4PU0) of vitamin molecules. The chemical structures of thirty-one vitamin molecules studied in this work. Among vitamin-based self-assemblies, D-BIO assemblies with higher piezoelectricity were used to fabricate PENGs for energy harvesting and human motion monitoring. (Image: Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge)
To demonstrate practical applications, the researchers created a prototype device using D-biotin crystals. When compressed with 47 Newtons of force (approximately 4.8 kg), it generated 0.8 volts of electricity. The device showed remarkable durability, maintaining consistent output through more than 5,400 compression cycles and exhibiting stable performance after three months of testing.
The team developed wearable sensors incorporating their vitamin-based generators to track joint movements. When attached to wrists, knees, shoulders, and elbows, the sensors produced distinctive electrical signals corresponding to different degrees of bending. This enabled precise real-time monitoring of body motion.
They also constructed an insole containing multiple vitamin crystal generators. During normal walking, the combined electrical output powered 12 LED lights, demonstrating sufficient energy generation for small electronic devices. This suggests promising applications in self-powered health monitors and wearable technology.
The research provides detailed insights into the relationship between molecular structure and electrical performance. Crystals with lower internal symmetry and stronger molecular polarization generated more electricity under stress. This understanding helps guide the selection and optimization of vitamin compounds for specific applications.
The vitamin-based approach offers several key advantages. Beyond their inherent biocompatibility, these crystals are biodegradable, cost-effective, and can be produced using straightforward methods. Their stable performance suggests immediate practical potential in medical sensors and other bioelectronic devices requiring safe, reliable power generation.
This work establishes vitamins as a viable material for creating bioelectronic components that harvest energy from natural body movements. The combination of good electrical performance, long-term stability, and complete biological safety addresses a critical need in medical device development. These materials could enable new advances in implantable sensors, wearable health monitors, and other medical technologies that require safe, sustainable power sources.
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