“Microinjection by ultrasounds opens new opportunities for medical devices manufacturing”
From the invention of the first man-made plastic in 1862, the plastic industry has grown exponentially in materials and techniques making impossible, nowadays, to imagine a modern life without plastics. With a vast expertise in plastic injection moulding processes, Optogenerapy’s partner Eurecat brings to the project its expertise on the manufacture of micro and mini plastic pieces by ultrasounds, a ground-breaking concept for the production of functional micro pieces.
In this interview, Encarna Escudero, specialist in polymer and elastomer processing at Eurecat’s Plastic Polymeric Materials unit, details how microinjection by ultrasounds opens a new field for the manufacturing of micro pieces for health applications and how the technology is being used in the Optogenerapy project.
Could you tell us about your work for the Optogenerapy project?
We are in charge of the implant manufacturing, this is to say, the integration of the beta interferon (IFN- ß) producing cells confined into the membranes and the wireless powered electronics, all protected with an outer case. We need to ensure that the materials we are working with are compatible with the membranes and we do not damage them during the manufacturing process (e.g. rupture, compression…) as the membranes have a structural function, but also allow the cells to live and feed themselves inside the implant. On top of that, the materials need to be skin contact harmless plastics. Specifically, we have tested several USP VI certificated types of polypropylene that meet all cytotoxicity requirements.
Which technology are you using for manufacturing the implant?
For manufacturing the device we are using conventional microinjection, insert moulding, in mould electronics and ultrasound microinjection with SONORUS equipment, the first ultrasound moulding machine based on the results obtained by Eurecat in several R&D European projects now being commercialised by the spin-off named Ultrasion.
In which aspects does microinjection by ultrasounds differ from conventional microinjection?
In microinjection by ultrasounds, the spindle that melts the plastic with electric heaters in conventional micromolding machines is replaced by an acoustic system that melts the plastic by means of ultrasonic waves. Compared to conventional injection, the microinjection by ultrasounds allows quick melting of reduced quantities of thermoplastic material and a better filling of mould cavities details. Because the melt flowability achieved by ultrasounds is better, the pressure applied is significantly reduced compared to other conventional microinjection machines. In many cases, ultrasounds allow the manufacturing of applications in a microscale impossible to produce by conventional injection techniques.
What are the main advantages of using microinjection by ultrasounds for the Optogenerapy project?
Basically, applying this technology to the development of Optogenerapy’s implant cell chamber offers major advantages for the moulding process of its very thin wall thickness, allowing the material to flow better and minimising the deterioration risks of the plastic parts and components (membranes, flexible electronics and a light guide).
With which challenges are you dealing with?
The main objective is to ensure that all functional elements are embedded hermetically and that the cells placed into the membranes can be fed freely so they can release the IFN- ß drug. To achieve this objective the challenge is to fit in one single application several complex technologies: high precision micromanufacturing, overmolding of flexible electronics, embedded optics and the use of implantable materials.
Which will be your work focus during the following months?
Right now we are developing the first prototypes of the implant, which will integrate the electronics developed by Eurecat’s functional printing technology unit, the optical guide and the cell chamber. These prototypes will allow our colleagues at ETHZ and INSERM to work in parallel with the biological research while we continue working on the plastic set of components conforming Optogenerapy’s solution. The next step is to manufacture fully integrated prototypes to be validated in in vivo lab tests.