MICRO MANUFACTURING THE IMPOSSIBLY SMALL
7/10/14 In the early days of the commercialization of micro manufacturing technologies, there was a lot of discussion about what constituted “micro” manufacturing. There was (and indeed still is) a recognized continuum from small to precision, micro, and then nano scale components and features. In general, it is safe to say that with every week that passes, we are able to manufacture — at volume — parts that only recently seemed impossible, and increasingly we are beginning to discuss parts and features in terms of nanometers instead of microns. We are forever moving down the size continuum, and today’s “micro” parts were yesterday’s pipe dreams.
Real “nano” manufacturing is actually unlike what we all understand as conventional manufacturing, and actually involves the self-assembly of parts and components at the molecular scale, this being a discipline still very much in its infancy, and involving manipulation and interaction of chemicals, building materials atom by atom.
Micro manufacturing, on the other hand, essentially involves the manufacture of products, components and features in a conventional way, using variations and evolutions of well-known “traditional” machining, molding, and automation technologies, that over time have become more and more precise. But sometimes, even for professionals like us at Micro Engineering Solutions (MES), who are at the forefront of developments in micro manufacturing, and who often times push the boundaries of the possible, there are times when it really does seem as if we are manufacturing the impossible.
It is all too easy to take for granted precisely what can be manufactured today. What makes working in such a dynamic area as micro manufacturing so stimulating is being able to see how innovation in industry is being driven by process and technology enhancements. Much of MES’s work is focused on the medical device sector, which makes this dynamism even more exciting, as developments often lead to life-changing or life-saving developments.
Across the industry in general, but in the medical industry in particular, the drive in terms of product and component design is towards miniaturization. In the medical sector, beyond the usual industrial desire for use of less material and weight savings, miniaturization is driven by the desire on behalf of medical product manufacturers to produce products that allow for ease of implantation or that facilitate new surgical procedures or treatments with minimal invasiveness.
Of course, there is a tradeoff between miniaturization and the actual function of a medical product. Smaller and smaller is not always better and better, and there are limits to the extent to which medical products can be reduced in size and still produce optimal patient outcomes. A few argue that there is a danger in some instances that the oft quoted design mantra that “form should follow function” can become lost as medical product designers continually strive for miniaturization. But in general terms, medical designers are forever pushing the boundaries of increased precision and reduced size in balance with part functionality and user ergonomics.
There are particular areas where continued requirements exist for efficacious parts that are as small as possible, for example in various in vivo diagnostic applications such as embedded sensors, in the development of intravascular ultrasound catheters, and for numerous micro-invasive technologies treating a variety of chronic medical conditions. Today, the minute scale to which micro medical parts can be produced is extraordinary, and is opening up treatment regimes and solutions to medical conundrums that seemed the things of fantasy until relatively recently.
Thin Walls and Complex Features
Just take a look at some of MES’s work and the recent developments in micro level manufacturing. Typically, with every day that passes we are able to fabricate smaller and smaller and more complex parts with thinner walls and finer and finer detail. And one of the key reasons why this is possible comes down to developments in micro machining which enable the design and creation of micro molds that allow the manufacture of such parts via micro injection molding.
These days it is relatively common-place for us to be able to micro mold parts in a variety of materials with 50 micron wall thicknesses, often with aspect ratios (length against wall thickness) of not far off 200:1. When applied to the medical device sector in particular this ability opens up massive potential in terms of less invasive and more efficient medical devices and diagnostic equipment.
Thin-walled components are key in facilitating the development of numerous medical devices and diagnostic equipment from stents to transdermal patches, and from endoscopes to biopsy forceps, sensors, and gears.
But for OEMs planning to work with this level of precision, the agency of a qualified and expert micro molder is vital. Beyond the fact that micro molding technology is evolved from “macro”-sized machines, the actual logistics of manufacturing in plastic at this size are radically different, and require an innate understanding of the unique contingencies that apply.
For example, being able to manufacture extremely thin-walled components is a product of a generous melt flow polymer, extremely accurate core-to-cavity alignment, and highly balanced flow path. Optimising the balance of all these variables is hugely demanding, and more often than not requires multiple design iterations. Never has there been a better example of why successful OEMs involved in the micro manufacturing arena work with the likes of MES as product development and manufacturing partners, not just subcontract job shops!
Many medical thin-walled micro products not only need to be able to be manufactured cost-effectively in volume, but they also need to perform in critical and often extreme conditions, meaning that every part of the design to manufacture and end use cycle needs to be considered, and a variety of regulatory and compliance criteria adhered to. All this means that getting the process streamlined and ensuring as few iterations as possible at the design stage is vital as failure to do so can have massive knock-on effects in terms of product development cost.
Micro Silicone Valves
Recently, MES was involved in the development of a silicone valve that is perhaps the smallest thin-walled micro project that we have worked on, and which truly shows the precision to which we can work these days.
This silicone valve is used in cartilage repair, and MES was able to put 84 million of them on one microscope slide. Each snowflake shaped valve was less than a cubic millimetre in size, was 100 microns tall, and 100 microns wide, with dimples / posts on top that was 3 microns in diameter and 3 microns deep. Made out of biocompatible silicone, the valves mimic cartilage, the specific application being cartilage repair in the toe.
The tooling to make such intricate parts is micro machined, and it is vital that the machining process delivers small, thin-walled valves with absolutely no flash, something that is a pre-requisite for any implantable medical molding.
Micro manufacturing is not the same as macro-scale manufacturing. While the development processes have the same names, they require a whole set of skills that are unique to manufacturing on the scale of a grain of sand. Every stage of the development process throws up challenges, from design, material selection, processing, handling, and of course validation.
Why not call MES today to discuss how we can help you push the boundaries of the possible in your product development projects. Please contact Donna Bibber at donna@microengineeringsolutions.com.
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