Torq-Lok® Braided Catheter Coating
A patented metal plating process that locks braid intersections together, increasing torque transmission, pushability, and radial force strength along with minimizing elongation & kinking.
What is Torq-Lok®?
Torq-Lok® is ProPlate’s patented metal plating process that locks the intersections of a braided catheter together, transforming a loose woven structure into a single, force-transmitting assembly. Rather than relying on a mechanical or adhesive bond, Torq-Lok® uses electroplating to fuse each crossing point of the braid, comparable to micro-welding every intersection in the structure.
The result is a braid that transmits torque, axial force, and radial force from the proximal end of the catheter to the distal tip with significantly less energy lost to deformation.
Torq-Lok® is protected under U.S. Patent 9,962,522, assigned to Professional Plating, Inc.
Why Braided Catheters Need Torq-Lok®
Braided catheter construction is widely used where high torque response, pushability, kink resistance, and steerability are required. The catheter must be stiff enough at its proximal end to allow pushing and manipulation, while remaining flexible enough at the distal end to navigate increasingly smaller and more tortuous vasculature.
In a standard braid, energy applied at the proximal end is lost as the wire strands slide past each other at their points of intersection. This reduces torque transmission efficiency and limits the precision with which a physician can control the distal tip during a procedure. Increasing braid pic count to compensate for this energy loss adds material cost, production time, and can stiffen the overall structure more than desired.
Torq-Lok® addresses this at the source by eliminating the ability of the wires to slide past each other at their crossing points, without changing the braid pattern, wire count, or wire diameter.
How Torq-Lok® Works
Torq-Lok® applies a metal plating layer to a completed wire braid, depositing metal at the points where wire strands cross. Plating thickness is tailored to the application, covering a usable range of 10 to 5,000 micro-inches, with a preferred range of 250 to 1,200 micro-inches and a typical target of 750 to 1,000 micro-inches, depending on the level of torsional stiffness required and the available profile budget.
The plated metal joins the wires together only at their points of contact, leaving the lengths of wire between intersections unattached. Those unattached spans are what preserve the bending behavior of the braid. The plating does have some effect on flexibility, and the degree of that effect depends on the braid construction, wire material, plating thickness, and application requirements. ProPlate tailors the core material compatibility, plating chemistry, and process parameters for each customer’s specific braid construction, wire material, and catheter design.
Compatible Wire Materials
Torq-Lok® has been developed and validated for braids constructed from stainless steel, tungsten, molybdenum, and nitinol wire, with stainless steel being the most common substrate. Wire cross-sections can be round, oval, rectangular, or other polygonal shapes, with round wire being the most common configuration.
Have questions about Torq-Lok® for your braided catheter design?
Torq-Lok® Performance Benefits
Preliminary testing of Torq-Lok® compared to non-coated braided catheters demonstrated significant performance improvements across multiple measures of torque transmission and structural integrity.
30-66%
Increase in Torque Response
66%
Increase in Torque-to-Failure
90°
Increase in Twist Before Kinking
Additional Benefits
- Improved pushability
- Controlled radial forces for more predictable device behavior
- Minimized elongation under axial load
- Elimination of cut-end unraveling at the catheter ends
- Reduced pic count potential, allowing a lower pic count, meaning fewer wire intersections per linear inch, while achieving equal or better torque performance, reducing material cost and production time.
**Testing was conducted on braided catheters with the following parameters: 4 French OD, 60 pic count, 12 inches in length, 2-over-2-under-2 weave pattern, 0.001″ x 0.004″ wire. Results may vary based on braid construction, wire material, and application-specific factors.
Torq-Lok® vs. Laser-Cut Hypotube Alternatives
For catheter designers evaluating braided versus laser-cut hypotube construction, Torq-Lok® targets the same performance limitations that drive teams toward a hypotube, without re-engineering an existing braided design. Read our white paper for a detailed technical comparison of braided catheters, laser-cut hypotubes, and how Torq-Lok® compares across key performance parameters. Read White Paper →
Engineering Advantages for Device Designers
Because Torq-Lok® increases force transmission efficiency with minimal changes to the braid’s physical footprint, it gives device designers flexibility that traditional braid construction cannot offer.
Reduced Pic Count, Increased Inner Diameter
Since Torq-Lok® allows a smaller diameter wire or lower pic count braid to achieve equivalent or superior torque performance, catheter designers can offset the profile contribution of the plating layer by reducing wire diameter or pic count. This approach can maintain or increase the inner diameter of the assembly while managing overall profile, creating more room for additional functional components inside the catheter.
Design Flexibility for Complex Geometries
Torq-Lok® can be applied to braided assemblies used in any device requiring improved torque transmission through a flexible braided structure, including flexible drive shafts and other torque-transmitting assemblies beyond traditional catheter applications.
An Established Process Requiring Application-Specific Development
ProPlate has developed and refined the Torq-Lok® process across a range of braid configurations, wire materials, and polymer core substrates. While the core process is established, each new application requires its own development and validation work to account for the unique combination of braid construction, wire material, polymer core, and plating parameters involved. The following are the key variables that must be characterized and validated for each specific application.
Polymer Core Compatibility
Braided catheters are constructed around a variety of polymer core materials, and each material reacts differently to the plating chemistries used in the Torq-Lok® process. ProPlate has run extensive trials across different core materials to determine appropriate process parameters for each substrate type.
Plating Thickness
The appropriate plating thickness for Torq-Lok® varies by application depending on the braid construction, wire diameter, pic count, and the level of torsional stiffness required. Thickness must be characterized during development to achieve the desired torque performance while managing the profile contribution of the plating layer. Each application requires process development to define and validate the correct thickness specification.
Consistent Adhesion
Reliable, repeatable adhesion of the plated layer to the braid is essential for consistent performance. ProPlate’s Torq-Lok® process has been tailored and validated to achieve dependable adhesion across production volumes.
Custom Tooling for Production Scale
ProPlate has developed custom tooling specific to the Torq-Lok® process to ensure consistent, repeatable results when manufacturing at production volumes, supporting a wide range of braid configurations and catheter lengths.
Application Examples & Technical Resources
Torq-Lok® Enhanced Torque for Braided Catheters
Braided catheters lose torque transmission efficiency when wire strands slide past each other at their points of intersection. ProPlate developed the patented Torq-Lok® process to lock these intersections together through selective metal plating. The result was a significant increase in torque response and torque-to-failure, with the unattached spans between crossings preserving the braid’s bending behavior.
Torq-Lok® vs Laser-Cut Hypotube
Braided catheter shafts lose torque where the wires cross. Compare braid, laser-cut hypotube, and the patented Torq-Lok® plating process, with the design parameters from US 9,962,522 B2.
Ready to discuss Torq-Lok® for your catheter program? Submit a request and our team will follow up.
Patent and Industry Recognition
Torq-Lok® is a patented innovation, protected under U.S. Patent 9,962,522 B2, “Braid Plating Method for Torsional Stiffness,” assigned to Professional Plating, Inc.
Since its introduction, Torq-Lok® has been recognized by the medical device industry as a significant innovation in catheter performance technology.
- 2015 MD&M West and Qmed Supplier Innovation Challenge — Finalist: Torq-Lok®
- 2016 BIOMEDevice Boston Innovation Challenge — Top 10 Finalist: Torq-Lok®
- Featured in Medical Product Outsourcing: “Electroplating Innovation Used to Enhance Braided Catheters”
- Featured in Qmed (now MD+DI): ProPlate’s Torq-Lok® process discussed alongside Vizi-Band® as engineered metal coating innovations for catheter-based devices
Frequently Asked Questions About Torq-Lok®
What is Torq-Lok® and how does it work?
Torq-Lok® is ProPlate’s patented metal plating process that locks the wire intersections of a braided catheter together by depositing a thin metal layer at each point of contact. The plating fuses the crossing points without attaching the wire lengths between them, increasing torque transmission while preserving the braid’s flexibility.
How much does Torq-Lok® improve torque performance?
Preliminary testing demonstrated a 30 to 66 percent increase in torque response, a 66 percent increase in torque-to-failure, and a 90 degree increase in twist before kinking, compared to non-coated braided catheters. Testing was conducted on a 4 French OD braid with a 60 pic count. Results may vary based on braid construction, wire material, and application.
Does Torq-Lok® reduce catheter flexibility?
Torq-Lok® plating bonds the wires at their points of intersection, leaving the wire lengths between crossing points unattached. While the process does have some effect on flexibility, the primary performance gains are in torque transmission, pushability, radial force strength, and kink resistance. The degree of flexibility change depends on the specific braid construction, wire material, plating thickness, and application requirements.
What wire materials is Torq-Lok® compatible with?
Torq-Lok® has been developed and validated for braids constructed from stainless steel, tungsten, molybdenum, and nitinol wire. Wire cross-sections can be round, oval, rectangular, or other polygonal shapes.
Is Torq-Lok® patented?
Yes. Torq-Lok® is protected under U.S. Patent 9,962,522 B2, “Braid Plating Method for Torsional Stiffness,” assigned to Professional Plating, Inc.
Can Torq-Lok® allow for a smaller pic count or smaller wire diameter?
Yes. Because Torq-Lok® increases torque transmission efficiency at each braid intersection, catheter designers can often use a lower pic count or smaller diameter wire while achieving equal or better torque performance than an uncoated braid with a higher pic count. This can reduce material cost and increase the available inner diameter of the catheter without increasing its outer diameter.
Does ProPlate manufacture Torq-Lok® at production volumes?
Yes. ProPlate has developed and refined the Torq-Lok® process across multiple braid configurations, wire materials, and polymer core substrates. Because each catheter design involves a unique combination of these variables, application-specific development and validation work is required before moving to production. ProPlate engages with customers during the development phase to characterize polymer core compatibility, plating thickness, adhesion performance, and tooling requirements specific to each application.