Diamond is primarily known for its hardness. A team from the University of Hong Kong has shown that ultra-thin diamond membranes can produce an electrical voltage when bent. This property opens a path for small sensors and autonomous devices.
The observed phenomenon belongs to piezoelectricity. In certain materials, mechanical deformation slightly shifts electrical charges and creates a potential difference. Diamond was previously considered non-piezoelectric.
(A) Piezoelectric effect of the ultra-thin diamond membrane during successive presses and releases.
(B) Timeline of discovered piezoelectric materials.
(C) Diamond membrane 5.08 cm wide and 1 μm thick, before and after deformation.
(D) The membrane moves closer to a negatively charged rod and moves away from a positively charged rod, then returns to its original shape.
The researchers did not use a cut stone. They fabricated a polycrystalline diamond membrane, thin and flexible enough to be bent without breaking. This unusual shape allows the material's response to deformations to be studied.
During bending tests, the membrane generated stable electrical signals. The team repeated the mechanical tests under several conditions to rule out external disturbances or effects related to material contacts.
The explanation likely lies at the boundaries between the numerous small crystals that make up the membrane. These grain boundaries do not all have the same atomic organization. When deformed, an electrical polarization can accumulate there.
This asymmetry then creates a potential difference between the two faces of the film. The mechanism differs from that of a perfect crystal, whose very regular structure does not produce the same effect. The material thus retains its mechanical properties while gaining an electrical function.
This combination is interesting for miniaturized systems. Diamond resists wear, heat, and many chemical environments well. Membranes capable of detecting deformation could therefore find a place in sensors intended for extreme conditions.
The authors also mention medical applications, particularly for implantable devices. Its biocompatibility and chemical stability are assets.
The result concerns ultra-thin polycrystalline diamond membranes, not ordinary diamonds. Future research will need to clarify the durability of the process and its large-scale manufacturing. It will tell whether this effect can become a practical solution for powering or equipping tiny devices.