Chemical etching of medical alloys and titanium

Medical alloys are typically characterised by their high strength-to-weight ratio and their biocompatibility. Also – crucially – medical alloys exhibit impressive corrosion resistance, which is of vital importance when used in the manufacture of implantable medical devices which are under constant attack from bodily fluids.

A common medical alloy is stainless steel which consists of chromium, nickel and molybdenum. It is the chromium in stainless steel that gives the metal its corrosion and scratch resistance, the nickel offers an even and polished finish and the molybdenum increases the hardness of stainless steel and helps sustain a cutting edge.

Cobalt-Chromium based alloys such as Elgiloy® are used in making orthopaedic implants. These materials exhibit excellent biocompatibility, are resistant to corrosion and wear and they have properties that replicate those of the body structures they replace.

In recent years, titanium has become of pivotal importance in the medical device industry. In common with other medical alloys, however, its strength and corrosion resistance – while being advantageous in end-use applications – make it an extremely difficult material to process. Traditional metal fabrication technologies struggle with the hardness of titanium and as photo etching effectively chemically corrodes metal, titanium’s impressive corrosion resistance presents numerous challenges for photo etching as well.

Precision Micro has invested heavily in the photo etching of titanium due to the fact that it is such a fundamental material in medical applications. Titanium’s corrosion resistance and biocompatibility as mentioned are of key importance, but it also has an innate ability to “knit” with human bone. As such titanium and its alloys are used in a variety of implant applications, including bone and joint replacement, maxillofacial and craniofacial treatments and cardiovascular devices, as well as for external prostheses and surgical instruments.

In 2014 Precision Micro invested 1m Euro in its titanium etching plant and process in response to market/customer demand. The etch machine and allied control systems were custom built to Precision Micro’s specifications and the titanium line is housed in a purpose-built, self-contained unit at the company’s premises in Birmingham, U.K.

This investment means that Precision Micro can now process all relevant medical alloys, including titanium and Nitinol, in sheets sized up to 600mm wide by 1500mm long and in thicknesses from 10 microns to 1.5 mm.

Photo etched parts are burr-and stress-free and require virtually no post processing. Being essentially an ambient process, etched parts suffer no heat-induced distortion or embrittlement during the process and materials maintain all their original mechanical properties.

With photo etching design complexity is not a limiting factor as component features are produced simultaneously from low cost, easily iterated digital tooling. This ensures a process which is economical, low-risk, with lead-times measured in days not months.