Aug 24, 2023
The piezoelectric effect is a fascinating phenomenon in which certain materials exhibit the ability to generate an electric charge in response to mechanical stress or deformation, and conversely, to deform when subjected to an electric field. This unique behavior arises from the arrangement of atoms within these materials, which creates an asymmetry in their crystal lattice structure. When pressure or strain is applied to the material, it causes the lattice to distort, generating electric charges on the surface of the material. This effect was first discovered by Jacques and Pierre Curie in 1880, and it has since found diverse applications across various fields.
Applications for the technology exist in developing actuators for precise motion control, sensors for measuring pressure, acceleration, and vibration, as well as in acoustic transducers like microphones and ultrasonic sensors. Additionally, piezoelectric materials are used in energy harvesting to convert mechanical vibrations into electrical energy for portable devices. This has the potential to power low-energy electronic devices in remote locations or even in wearable technology, reducing the dependence on traditional power sources.
The unique properties of piezoelectric materials has sparked an interest in using them to power implantable medical devices, to eliminate the need for traditional batteries. However, most of these materials are rigid and brittle, and worse yet, they frequently contain toxic materials like lead and quartz. Amino acids stand apart as a biocompatible alternative, but in order to exhibit a strong piezoelectric effect, the molecules must be aligned in the correct orientation. Producing films of amino acids, oriented in the same direction, has proven to be too challenging at scale to date.
A new technique developed by researchers at the Hong Kong University of Science and Technology may soon enable the manufacturing of biocompatible and biodegradable medical devices. They have demonstrated that their methods can produce self-assembled, thin layers of amino acids with an ordered orientation that cover a large surface area. These thin films exhibit a strong piezoelectric effect that can be leveraged to generate electricity from muscle stretching, breathing, blood flow, and other body movements. In the future, these sheets could power pacemakers, biosensors, and other devices. And when the job is done, they can safely dissolve away.
In the course of their research, the team found that the amino acid β-glycine has an exceptionally strong piezoelectric response. As such they fabricated nanocrystalline films of this amino acid with a bio-organic film printer using the electrohydrodynamic spray method. During the spraying, an electric field is applied between the nozzle tip and the conductive support to aid in the formation of nano-micro droplets. Due to the tiny size of the nano-micro droplets, water evaporates away very quickly. And this, in turn, serves to orient the β-glycine molecules in a consistent manner in the resulting biomolecular film.
One of the researchers leading the work noted that their “study shows uniformly high piezoelectric response and excellent thermostability across the entire β-glycine films. The excellent output performance, natural biocompatibility, and biodegradability of the β-glycine nanocrystalline films are of practical implications for high-performing transient biological electromechanical applications, such as implantable biosensor, wireless charging power supply for bioresorbable electronics, smart chip and other biomedical engineering purposes.”
At present the team is continuing to refine their methods with the hopes of making the films as flexible as natural biological tissues. They also are investigating ways to achieve low-cost mass production of the films. After these goals have been met, they intend to conduct experiments in animal models to show the potential of the new technology to power implantable medical devices.