A multitude of medical devices require hollow wires, ranging from the tools for keyhole surgery to vascular probes. The ideal wire would be strong, flexible, have a definite lumen (cavity) size and be easily manipulated. Fort Wayne Metals has developed helical hollow strand (HHS®) tubing - which has a unique structure that allows its torsional properties and lumen size to be fine-tuned.
AZoM spoke to Austin Cisna and Jay Wehrle, of Fort Wayne Metals, about their HHS® tubing, the different applications it has been used in and the level of service and customization that Fort Wayne Metals can provide.
What are the key differences between Helical Hollow Strand (HHS®) tubing and other types of tubing?
HHS® Tube is composed of 6-18 individual wires (stranded together like the threads of a rope) per layer, with up to three layers. This product line has matured into a highly customizable platform for developing solutions to navigating tortuous paths while delivering torque.
Unlike other products, HHS® Tube stranded properties can be configured to deliver torque in both clockwise and counterclockwise rotations, tailored to the flexibility needs of a medical device manufacturer. It can come in a variety of sizes, from a large working lumen to as small as the human hair.
These are all available avenues for our customers who require HHS® Tube design, and all of this can be carried out quickly and cost effectively.
What applications are HHS®Tubes used in?
HHS® Tube can be applied to many areas of the medical field. These range from being used in channels such as endoscope shafts, guide channels and in catheters, as well as in advanced medical devices such as orthopedic drills, the laparoscopic instruments used in keyhole surgery.
HHS® Tube is primarily used in the medical device industry, but the diversity of materials, range of sizes and ease of post-processing operations mean that the HHS® Tube is versatile enough to meet the needs of many non-medical applications.
HHS®Tubing can be used as a guide shaft for endoscopy. Shutterstock | flywish
What behavior has HHS®Tubing been designed to demonstrate?
The distinctive characteristic of HHS® Tube is the working lumen, which many applications utilize for guidewire delivery.
The multiple helically formed filaments give the HHS® Tube its characteristic flexibility while also the ability to deliver torque. From product to product, these tubes can be changed to focus on the needs of the customer’s design criteria.
What properties of HHS®Tubing make it suitable for use in biomedical devices? How can its structure be changed to alter these properties?
HHS® Tube is designed to be integrated into other devices and assemblies.
At Fort Wayne Metals, we offer the assembly design, manufacturing and fitting of HHS® Tube products. We can also offer the addition of crimps, beading, laser welding and assembly of unique parts. In addition, we can also process the wire using methods like swaging, which creates a stiffer product and allows it to have a smooth interface with other devices and fittings.
A variety of coating services are available for low-friction interfaces or fluid seals.
What effect does the inclusion of multiple layers have on the behavior of the HHS®Tubing?
Single layer HHS® Tube does allow for some torque delivery in both clockwise and counterclockwise directions. The nature of the product means that, like a screw, it has one direction of primary rotation.
While one direction of primary rotation is suitable for many applications, torque in both directions within the same part is essential for many more. By layering HHS® Tube in opposing directions, the difference in torque performance can be reduced while gaining other advantageous characteristics.
Typical multilayer HHS® Tube can be designed with different monofilament wire sizes at each layer to influence compression, elongation and improve crush resistance. These advantages allow the product to hold the lumen open in high-precision applications.
Most importantly, with so many of our products reaching the hands of surgeons, the product feels noticeably different from traditional wire.
How would the specification of HHS®Tube being used neurologically differ from that being used in an endovascular environment?
The multitude of applications that this productline touches is tremendous.
The same product family can exist in sizes in excess of an eighth of an inch to about the size of the human hair. Size, flexibility, material and the number of layers are some of the characteristics that can be tailored to suit the needs of the customer.
A device that is meant for neurological stimulation will require incredibly fine wire filaments to be flexible enough to be manipulated by the surgeon. A device used in the vascular system may require extreme flexibility at a larger OD, or good compression resistance to deliver complex tooling to the site of a blood clot.
Even larger endoscopy applications may need to be long, large in lumen working channel, stiff and capable of delivering good flexibility through the intestines.
HHS®Tubing can be used for neurological surgery and in electrostimulation. Shutterstock | Image Point Fr
What alloys can HHS®Tubing be made from?
The diversity of materials that Fort Wayne Metals is capable of processing, as well our collective expertise from four decades of metallurgy, allow us to provide HHS® in a variety of alloys.
Most HHS® Tube is constructed from biocompatible materials, which is key to success on the market. Since many applications are not permanent implants or are non-implantable devices and surgical instruments, 300 series stainless steel is the most commonly used alloy family.
The excellent strength properties and minimal cytotoxicity of stainless steel alloys, as well as the ease of cleaning, make it the most commonly used alloy in HHS® Tube. Cobalt Chromium and Nitinol alloys are also used in some applications.
Does Fort Wayne Metals provide advice on which HHS®Tube specification is best for a certain application?
Fort Wayne Metals is eager to accept and review all inquiries for HHS® Tube design and use.
Continuously improving our design techniques to quickly provide effective solutions for our customers is of high importance to Fort Wayne Metals. We believe that equipping our customers with the highest quality information and an honest evaluation of the opportunity presented to us will result in the best product for their use.
Can Fort Wayne Metals supply custom made HHS®Tube?
While we do offer some HHS® Tube sizes as stock items, our customers prefer to work with Fort Wayne Metals engineers to design custom HHS® Tube that suit their needs. We maintain a large stock of samples in order to quickly respond to inquiries and requests.
Where can our readers find out more about Fort Wayne Metals and HHS®Tubing?
Please visit our website. Readers can learn about the many products and services that we offer, including HHS® Tube. The Contact Us page will help readers find their local sales representative to start the conversation about which products best fit their needs.
Fort Wayne Metals also attends many industry trade shows; for a full list of our attendance please see our calendar.
About Austin Cisna
Austin Cisna graduated from the University of Iowa with a Bachelor of Science in Biomedical Engineering and a minor in Computer Science. He began his career at Fort Wayne Metals as an Engineering Intern in the summer and winter of 2015, and accepted a full-time position as Process Engineer for HHS® Tube in July 2016 following his graduation. In this role he designs and develops HHS® Tube, improves the process, and develops new production technologies.
Austin grew up in the suburbs of Chicago, but is no stranger to Fort Wayne, having visited family for holidays and special occasions since he was a child. In his free time he enjoys spending time with his fiancé, traveling, running, camping, drawing and tinkering with 3D printers.
About Jay Wehrle
Jay Wehrle is a Fort Wayne native with twenty years of manufacturing experience. He graduated from Indiana University—Purdue University Fort Wayne with a Bachelor of Science Degree in Mechanical Engineering Technology.
In July of 2016, Jay joined Fort Wayne Metals as the new Process Engineer in the Custom Assembly department at ABG; his responsibilities include HHS® finishing, laser ablation operations, EDM cutting- and laser welding.
Prior to joining Fort Wayne Metals, Jay worked at Novae Corporation in Markle, Indiana, for twelve years in various engineering and management positions. Before Novae Corporation he worked for Poly-Hi Solidur as a production supervisor.
Jay enjoys spending time with his four daughters, who keep him busy traveling to soccer games and dance competitions. In-between family activities, he enjoys running and cycling.
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