Development of piezoelectric solutions for cold plasma generation dedicated to biomedical applications – PIEZOBIO

This global development involves the crossing of a set of technical and technological locks, each carried by one of the partners. Each lock is therefore an objective to overcome during the project.
- The design of the piezoelectric element: electrical performances are essentially ensured by an appropriate design of piezoelectric ceramics. It is therefore a question of defining the dimensioning criteria and of elaborating a rigorous method to reach the optimal design.
- The realization: according to the complexity of the defined design, the synthesis of the material and the manufacture of the piezoelectric ceramic constitutes a technical challenge.
- Power supply: The electrical supply stage of the piezoelectric element constitutes an important part of the operation, whether to ensure the bactericidal performances or the preservation of the integrity of the plasma generator.
Surface treatment: in view of the uncertainty of the effects of the plasma produced on the surface of the ceramic, it is necessary to consider preventive solutions of deposits
- Bactericidal validation: this is the aim of the project, namely to evaluate the bactericidal capacities of the cold plasma generated from this method of plasma generation.

Over the first half duration of the project, each partner has confirmed the locks under its expertise and identified difficulties. This step was made possible by using two equipments: a first is from a commercial equipment diverted from its initial use, and the second being a prototype realized during the project.

Results by partner:
- The LMCPA initiated and resulted in the design of several pre-prototypes of piezoelectric ceramics of various geometries, in order to demonstrate technical mastery. Appropriation of the steps of production of «hard« ferroelectric powders, sintering, machining and polarization.

- SINAPTEC started with the technical study of the commercial generator. This study proved to be relevant for verifying the requirements of the electrical drive. Then SINAPTEC has used its NEXTGEN equipment, which facilitates the exploration of various driving modes.

- ANIOS has applied a standardized procedure to qualify the bactericidal effect of the piezoelectric plasma generators. These tests, first conducted with commercial equipment, revealed poor performance. On the other hand, a second test campaign with the prototype of LAPLACE highlighted very encouraging performances, reaching at best the limits of detection.

- CIRIMAT has developed a characterization protocol and an «identity card« of the piezoelectric transformer in the reference state based on its chemical composition, granular morphology, crystal structure or polarization state.

- LAPLACE has made numerous samples of the prototype for providing every partner to start their preliminary tests. It also started the theoretical study (analytical and numerical), in order to build the tools necessary to the definition of the optimal design the second generation prototypes.

Decontamination and disinfection are major concerns in many sectors of activity such as medical, pharmaceutical and food industry.
Up to now, the project aims to demonstrate the capabilities of piezoelectric technology to meet the requirements of decontamination for the medical community.
In the light of the results, the decontamination process must then be promoted and then applied to a specific objective. Depending on the numerous possible final applications, the implementation of the piezoelectric technology could take very different configurations which could not be developed in the current project. This is why an accompanying service of the Eurasante EIG was programmed in order to study the applicative perspectives, in the health, nutrition and biology sectors, both in national and European level.

After 18 months of the project, the scientific publications and communications about the intermediate results are either being written or submitted. LAPLACE has carried out public lectures :

- participation of Jordan Stekke in «my thesis in 180 seconds«, edition 2017
- participation in «a coffee with a young researcher?«, 30 May 2017. Public talk in Toulouse.

This project consists in the study and development of a technological solution using piezoelectric materials for the production of plasma discharges at atmospheric pressure. The developed tool must be able to satisfy the specific requirements for the decontamination of the medical equipments such as endoscopes and narrow tube devices (catheter).

Due to its remarkable physical and chemical properties, plasma discharges have become a subject of interest in the biological area, for over several decades due to their non thermal and reactive properties which allow the interaction with living tissues, cells and bacteria and predispose it to a multitude of applications, especially biomedical ones. Cold plasma is an efficient, non-aggressive and low heating solution, used for direct treatment of medical subjects and also for surface treatment without degrading characteristics / essential properties. Thus, cold plasma can be used for high level decontamination, especially for heat-sensitive materials and can replace toxic products and limit superfluous manipulation harmful to the treatment. If a lot of academic work is devoted to the understanding and improvement of the process, existing industry solutions do not completely take advantage of this technology, especially for sterilization issues. Nowadays, only one commercial equipment relies on a plasma treatment during its sterilization process.

Besides, if some studies are devoted to the electrical dimension of the device, the architecture of the discharge generators as a way of improvement is not much investigated, particularly for the small size devices (for manual or endoscopic use). The need for high-voltage, for high electronic charge quantity, associated with operational constraints inherent in the medical area can restrict the conventional generation techniques.
Nowadays, the idea of producing plasma discharges through piezoelectric effect, particularly with the use of piezoelectric transformer, has become totally attractive and original. The characteristics of this solution, such as low voltage, high permittivity, the miniaturization capability or controllability, favorably predispose it for the targeted area. The ability of these piezoelectric materials to generate spark has long been known and utilized in elementary ignition systems such as electronic lighters. It is now to take advantage of these dispositions to maintain the surrounding gas in a state of cold plasma. While some academic illustrations demonstrated this potential for generation and facilitated the understanding of physical principles in place, it becomes necessary to realize devices specifically designed and optimized for plasma generation, especially devoted to biomedical applications
In addition, preliminary studies conducted in recent years in the laboratory of the project manager, have highlighted two favored ways of improvement: the design of piezoelectric transformers and their supply strategy. These two aspects constitute the core academic target of this collaborative project which it is necessary to associate the checking of biocide capabilities.
With the industrial partners Anios and Sinaptec, this consortium have as an ambition to combine their skills in order to develop a solution overcoming the current restrictions when it comes to treat the thermo-sensitive material, especially narrow tubes. This will be achieved by working on the design of the discharge generators based on piezoelectric materials. The development of such a system would allow obtaining a rapid and precise solution easily usable for clinic and biomedical applications, affordable to anyone and free of use contrary to existing solutions slightly restrictive.