Virtually Optimize The Finest Structures In Microfluidics

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-06-05 00:21

Medical technology products in general and implants in particular are subject to the highest requirements for precision, quality and reproducibility and at the same time have to cover a wide range of different materials. As miniaturization progresses and functional integration increases, product and component surfaces also have to take on special functions in order to achieve medically, biologically or technically advantageous properties

A challenge also arises from the increasing stress on implants due to increasing life expectancy, the desire for mobility in old age and increasing obesity. The lifespan of implants in turn is decisively influenced by the healing process and the growth behavior of the tissue, the avoidance of bacterial colonization and the wear behavior.

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Edit surface properties

The growth core "Mikrolas - Surfaces shaped by photonics" (see box), in which the use of ultra-short laser pulses enables a qualitative leap in the processing options of different workpieces and materials, addresses these problems. The surfaces of, for example, metals or ceramics, but also of transparent or thermally sensitive materials such as plastics or fiber composites, can be processed efficiently and without residues. Surfaces can also be specifically modified to achieve special technical or biological properties. As a result, surface properties such as wettability, abrasion or wear resistance and diffusion properties can be influenced depending on the location as well as the interaction of the functionalized surface with cells for the improved ingrowth behavior of an implant or its antimicrobial properties.

About the growth core "Mikrolas - Surfaces shaped by photonics"

The growth core (an initiative funded by the BMBF) "Mikrolas - Surfaces shaped by photonics" is intended to combine technologies from various research areas of ultra-precision machining and further develop them for industrial production, so that the partners in the growth core can use these technologies for their applications.

With ultra-short laser pulses, surfaces can be specifically and precisely changed in order to achieve special technical or biological properties. The ultrashort pulse laser is a relatively new process with which any material can be processed with the highest precision. The laser can drill, cut, mill and structure surfaces in the micrometer range. He can drill holes that are thinner than a human hair. For this purpose, the laser beam is bundled over a lens and directed onto the surface. The material to be removed is quickly heated without melting, so that it evaporates. In this way, the laser processes the smallest areas in the shortest possible time.

Targeted optimization thanks to simulation

However, the exact interactions of micro- and nanostructured surfaces with the surrounding media of the implants are hardly known in detail. While experimental and analytical methods for the analysis of such surface interactions cannot be used or can only be used with disproportionately high costs and time, virtual methods enable a systematic, very detailed and "transparent" approach. The technical and biological properties of the photonically functionalized surfaces are to be predicted and optimized using numerical simulation (in silico). Depending on the application, design processes are developed on this basis that enable a targeted optimization of the surface structuring.

ASD Advanced Simulation and Design GmbH from Rostock specializes in simulation-based product development and has developed appropriate processes for the design and optimization of surface modifications for selected medical technology applications as part of its growth core.

Virtually to the right microstructure

Hip endoprostheses are one application. In clinical practice, these still have a relatively high revision rate, so they often have to be replaced prematurely. Reasons for this can be the release of abrasion products from the surfaces and thus faster wear due to abrasion particles in the joint gap. The tribological effect of microstructural modifications to the pair of sliding surfaces of the joint endoprostheses was investigated using numerical flow simulations for such a problem.

The simulations showed a clear effect of the applied deterministic surface structures in the size range 5 to 50 µm on ceramics, medical stainless steel or plastics with regard to the sliding conditions in the joint gap. In particular, the viscosity of the non-Newtonian synovial fluid and thus its carrying and lubricating behavior as well as the local transport of friction particles are strongly influenced by the shape and size of the surface modification. The simulation-based selection of suitable microstructures to increase the lubrication effect and implant life before carrying out corresponding rheological and tribological tests significantly reduced development time and costs.

Dossier simulation

How simulation improves product development

Make connections visible

The simulation-based investigation of the interaction of mechanical surface modifications on implants with surrounding tissue also enables prediction and optimization of relevant functionalities in the early design stage. Bone is a living material that can adapt to changing load conditions by changing its structure. The new simulation methods take into account the relationships between the topology of a microstructured surface and its effects on the growth behavior of cells.

In the case of dental implants, it is interesting to see how microstructured surfaces influence the implant-bone interaction. In addition to the modified growth behavior of cells on the implant surface, a surface modification can also change the stresses or strains in the bone and implant. So it is possible that additional voltage peaks have a positive effect on bone remodeling processes. On the other hand, certain mechanical loads should not be exceeded in order to avoid permanent damage to the bone tissue. The simulation model also analyzes the effects of microstructured surfaces of a dental implant on its insertion behavior and stability in the jaw. This means that the great potential of laser structuring to generate a defined, cell-selective surface with section-related roughness design can be used in a targeted manner.

Simulation lowers development costs

In summary, it can be said that with the method of virtual product development described, a significant reduction in development times and costs can be achieved in the industrial implementation of modern surface modifications. In the case of medical technology products in particular, not only the possibilities of predicting physical-technical functional parameters but also of biological interactions are very promising.

simulation

Realistically map the smallest volumes of microfluidics

* ASD Advanced Simulation and Design GmbH, Rostock