Overcoming Engineering Challenges: Developing a Tiny Robotically Steerable Guidewire

Posted by Brian Buntz on February 15, 2013

As a company that develops medical products that typically comprise micro-electromechanical systems (MEMS), our greatest engineering challenge is rooted in the sheer physical size of our devices. For example, our flagship product is a robotically steerable interventional guidewire with a diameter of 0.014 in. (0.36mm)β€”the IntelliWire. Equivalent to just two strands of human hair thick, the core of this device houses an array of electrical and mechanical components, which collectively make up a proprietary multi degree-of-freedom motor and its supporting systems. Each of these components must be precisely manufactured and assembled to tolerances of much less than the size of a dust mite in order to ensure optimal operation and functionality. As a result, our most stringent constraints are derived from the capabilities of cutting-edge microtechnology production.

The electrical and mechanical components in the IntelliWire guidewire must be manufactured to tolerances smaller than the size of a dust mite.

Of late, we have observed a steady paradigm shift in microtechnology. In the early years, practical MEMS devices were largely confined to thin-film technologies, and were fabricated using silicon chip processing capabilities. Whilst this bottom-up approach is highly scalable, repeatable and cost-effective, many problems cannot be solved via thin-film technologies alone. In the case of actuators and motors, thin-film devices tend to produce high actuation speeds, but with low stresses and strains. In a practical sense, this translates into actuators that produce only minuscule forces, which are often orders of magnitude lower than required for the application at hand. With this, there is a clear and demonstrable need for top-down, bulk technologies to complement their thin-film counterparts. Here, the term top-down refers to more traditional forms of device manufacture (such as piecewise machining and assembly), and it is this need that is driving more companies to develop and manufacture top-down MEMS devices.

For a long time, there has been a wide gap between the manufacturing envelopes of bottom-up and top-down methods, but this is slowly changing too. Device designers now have the option of using complex parts as long as 1 mm that are grown via a bottom-up method. These parts can be produced with remarkable vertical and horizontal resolution, are highly repeatable and are cost-effective for large-scale production. However, there are still many devices that cannot be produced via even these advanced bottom-up methods, giving rise to a continued reliance on top-down manufacturing approaches. Striking the right balance between top-down and bottom-up production is typically the greatest challenge that micro-device designers face.

Geoff Rogers is one of the directors of IntelliMedical Technologies, an Australian startup company that specializes in the development of microscale medical devices. They are currently developing a steerable 0.014-in. guidewire based on proprietary technologies, as well as other devices for use interventional cardiology, neuroradiology, and other minimally invasive procedures.