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Whether testing for voltage withstand, inductance, capacitance, resistance, or triboelectric noise, we perform a variety of electrical tests on the custom cables we manufacture every day. Come take a virtual tour of our lab and see a sample of the tests we regularly offer.
When used in medical devices, wires and cables must meet exacting standards developed to ensure that the finished products will always perform as intended, with infinitesimal failure rates. Nowhere are those requirements more stringent than for invasive devices which have come to play a central role in both diagnostic and therapeutic applications for a wide range of diseases and conditions.
To get a better idea of the capabilities needed to meet such high standards, we recently spoke with Mike Tkalcic, Project Design Engineer here at New England Wire Technologies to learn more.
Q: In terms of the attributes that customers typically specify, how would you compare the requirements for medical products to those for other types of products?
A (Mike T.): The requirements for medical devices are more complex and often more demanding than those of nearly any other industry. Depending on the complexity of the device, developers may need to specify not only the basic physical attributes of the cable, like size and shape, but also their biocompatibility profiles, flexibility, lubricity, flex-life, performance after sterilization, and other characteristics. Obviously electrical performance is also critical.
Q: The attributes required for cables used in medical applications may be specific to a particular product, or even a particular model. What kind of medical products are the most demanding?
A (Mike T.): Cables that have stringent electrical requirements. Many advanced medical devices require signal wires to carry high-end video signals, and they are being expected to perform at higher and higher frequencies. Signal integrity is critical, so the wires are expected to function perfectly – even after physical abuse, such as being run over by a hospital gurney. Electrical characteristics such as insertion loss and jitter can’t be compromised in such situations; otherwise the video signal degrade.
Q: How do customers typically specify materials for the various elements of a cable, and what are some of the key implications of material selection?
A (Mike T.): One of the first decisions that customers need to make is whether the cable is for single use only, or if it is expected to be used over and over. Multiple-use cables have specific sterilization requirements that need to be considered when selecting compounds for insulation and jackets. Another consideration is whether the cables will be continuously flexed – a factor that will influence the proper selection of conductor type and stranding. Incorrect selection of these materials would undoubtedly result in cable failure or reduced life cycle.
Q: As medical devices have become more complex, requirements for electrical performance have also increased. How do these requirements determine the types of cables needed for a particular device?
A (Mike T.): Designs for today’s medical devices often include quite specific parameters related to miniaturization, high- or low-temperature performance, low triboelectric noise, and signal integrity. Our twinaxial cables can often be optimized to meet the needs of such medical applications. We also offer low-noise options for signal applications that undergo mechanical shock, vibrations, or repeated flexing typical of medical device applications.
Q: For many medical products, miniaturization is a natural outcome of clinical experience and technological advances in a variety of areas. How does the trend influence the attributes of cables used in such products?
A (Mike T.): The trend toward miniaturization is especially pronounced among permanently implantable devices and surgical products, including devices such as endoscopes that support minimally invasive surgery. Our miniature and microminiature coaxial cables are designed to meet the particular impedance, capacitance, and other exacting electrical requirements of such miniaturized devices.
Q: In addition to requiring excellent signal integrity, the cables used in some devices must also be very flexible and capable of maintaining flexibility after sterilization, while also being robust in the environment they are used within. How do these requirements translate into options from which customers can select?
A (Mike T.): We have a proprietary design reinforced silicone rubber jacket option called NEWtuf® that provides three times the tensile strength of silicone rubber and exhibits reduced distortion as a result of elongation. We also provide custom multi-conductor cables that can utilize a range of different types of conductors, shielding, and insulation options to address both flexibility and durability concerns. Specially processed, finely stranded conductors also contribute to ultimate flexibility, extended flex-life, and resistance to fatigue.
Q: The selection of coatings used in a cable can also influence its suitability for medical applications. What considerations do device developers need to address when specifying coatings for their cables?
A (Mike T.): NEWT offers both parylene coating and our proprietary SLEEK™ coating for silicone rubber cables. Both parylene and SLEEK™ provide optimal lubricity for situations where low friction, easily cleanable cables is a must, such as in a hospital or surgical setting. These coatings are permanently bonded to the silicone cables, are biocompatible, sterilization and autoclave stable, and add virtually no thickness to the final cable dimension. Parylene is typically applied to piece lengths and requires masked edges for bonded connections, while SLEEK™ is applied in a continuous process and is overmoldable, which is ideal for situations where long continuous lengths are a priority.
Q: Many medical products must comply with specific performance standards, but what about new products, or product applications, for which no standards exist? Can NEWT help companies that are in the process of testing components for suitability in their applications?
A (Mike T.): Yes, we can help in narrowing down the range of cable options to a few good candidates that the customer can then test. Often, the required cable has a few critical components. We can quickly prototype these components and perform specialized electrical and mechanical tests, providing feedback to help customers in their determination. These components can then be built into the finished cable, often saving time and money.
Q: What about the overall configuration of cables used in medical products? How much flexibility do medical product developers have when selecting cables from NEWT?
A (Mike T.): Custom design of cables is really “who we are” at NEWT, so we work closely with customers to develop and supply the exact cable required for their application. Marrying the customers’ needs with our design and manufacturing experience produces the most ideal cables for each application.
Q: What are the strongest trends affecting cable selection for medical devices, and what role do you see NEWT playing in addressing those trends?
A (Mike T.): Miniaturization remains a very strong trend amongst medical products, and this single goal carries with it a host of new technical requirements in areas such as more stringent signal transmission requirements for video and other data, long flex-life, increased lubricity, and so on. These increasing demands will continue to shape the design and development of future cables for medical applications. Custom design of such cables fits perfectly with NEWT’s core capabilities and products. We will continue to strive to be the market leader, working with our customers to achieve success in this cutting-edge industry.
Thanks Mike!
Born in Montreal, Quebec, Canada, Mike graduated from Dawson College with a degree in Electrotechnology. Mike has lived in New Hampshire since 1992, almost 20 of those years working for New England Wire Technologies. He works in our Engineering Design Department with a prime focus on customer’s special projects.
Interesting fact about Mike: he got his first computer in the 80’s, a Hyperion, which boasted 256 kB RAM. What a deal for almost $5000!
Nowadays he enjoys spending his free time with his wife, five children, and two grandchildren. Leisure time is spent in the woods or on local ponds, getting greasy tinkering on small engines, or growing a variety of hardneck garlic.
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In the short video here, we’ll walk you through the initial steps in working with NEWT on your custom cable design and will introduce you to your NEWT team members who will be communicating and collaborating with you on your project. Take a look!
Our very own Design Engineer, Tom Paquet, describes the most important features of good robotic cable design. Watch now!
The evolution of robotics and automation have transformed the modern manufacturing process. The intelligent factory of the future requires a level of flexibility and sophistication never before seen. From advanced sensors to autonomous motion control, components that can withstand ever increasing extremes in environment and performance will be imperative to remain productive.
We sat down with New England Wire Technologies Design Engineer, Tom Paquet, to pick his brain about the special anatomy and design behind today’s robotic cables. Let’s find out about the unique features required to support one of the hottest industries in the marketplace…
Q: So Tom, what kind of cable performance requirements do you typically see for robotic applications?
A (Tom): Honestly, we see just about everything. With robots being used for an increasing number of applications, there are requirements beyond just power, like signal, data and high voltage situations. It’s always about “where is this cable going to live?” That is, what environment will it be in? It’s important for us to understand if there are conditions that over time could compromise the integrity of the insulation. If it’s in a medical application, there are typically stringent cleaning requirements that we need to address. It’s also really important that we understand how the robot is going to move and what parts may rub on the cables, so designing for durability and sometimes abrasion, and always flexibility and flex life are critical.
Q: Can you explain the difference in the flexing movements required for robotics?
A (Tom): We see requests for cables to handle bending, torsional flexing, rolling, and combinations of all of those. Typically with robotics, flex life is more critical than overall flexibility.
Q: So, what is the difference between flexibility and flex life?
A (Tom): Flexibility is how easily the cable moves when handled. Almost all requests we see have a flexibility requirement in terms of how easily the cable moves, or how limp or “dead” it is when it lies on a surface. It can be tricky with robotics, because all of that movement you gain from flexibility is actually causing micro-movements within the cable which introduces friction and stress points which can create a weakness that eventually becomes a failure over time.
Flex life is a function of how many times you can flex the cable. Generally, flex life is given in the terms of “cycles”. When you bend something back and forth, we call that one cycle. So something that is very flexible may only have a few hundred or thousand cycles before it fails, depending on the cable construction. But something designed for very good flex life may withstand hundreds of thousands or millions of cycles, which is critical for robotics applications. Getting the correct balance between flexibility and flex life is super important in robotic design.
Q: What design features are important to promote better flex life?
A (Tom): The first step is to fully understand what type of motion the robot will be performing. So we need to discuss if this is a bending application, a torsional application, or something else as that can make a difference in some of our material choices.
Q: And what are the special material considerations for good flex life cables?
A (Tom): We’re almost always looking at alloy stranding for the conductors because they are harder and therefore deform less plastically. Without getting too much into Metallurgy 101, all materials first deform elastically and then plastically. So if you can bend something and it will return to its original shape, that’s an elastic deformation. If you bend it and it doesn’t return, that’s a plastic deformation – which is basically just “damage”. Harder metals, like alloys, can withstand more wear and tear before developing these imperfections, so that’s why alloys are a good choice.
Using plastics that will not fatigue quickly and fail is critical. Very flexible plastics tend to have poor flex life, and for the very same reason as alloys – you don’t want plastic deformation, you are looking for the elastic deformation. So we tend to use hard plastics for the primary conductors like polyesters or fluoropolymers. The jacket insulation should have a nice, tight fit to hold all of your conductors together and get a good bond, which is a good reason to use a polyurethane as that already has naturally good flex life and it is very abrasion and cut-through resistant.
Q: Why is cable design and geometry so important?
A (Tom): I mean, ideally we want an entirely symmetrical cable with all identical conductors – this ensures that everything equally shares any sort of stress burdens. In reality that hardly ever happens, so we have to be able to identify the weakest links, fortify them if possible, and put them in low-stress positions. Larger cables allow for more mechanically robust designs and larger bend radiuses, but real estate may mean there is less room for the cables in the overall design. Sometimes by the time people get to the cable portion of their finished robot design, they’re left with pretty minimal space for the cable to live – “this is the space we have left, what can you put in there to accomplish these goals?”
Q: Does NEWT provide testing for robotics cables?
A (Tom): We do offer a battery of test options that can help mimic real-life performance, allowing us to provide customers with reliable results. For example, for robotic designs, we commonly perform traditional flex testing which is often referred to as a “tick-tock” test for bend endurance, torsional stress testing, and rolling torsional testing which is a combination of torsional and flex testing. If customers have special testing requirements, we’re always happy to work with them to develop custom flex tests as well.
Want to see a quick video tour of our Mechanical Testing Lab? Click here.
Q: Are aesthetics important for robotics cables?
A (Tom): The way the end product looks is always important, especially when the cables are visible to users within the environment. You want the product to look professional. For medical robotics, there is a focus on clean, smooth, light-colored, probably glossy finished, and easy to clean cables. For other robotics the aesthetic may lean more toward something “cool” looking, and may use neon or bright colors. Onsite at NEWT, we have a custom color lab where we do color matching and custom color formulations for a wide variety of compounds and finishes, so the options are nearly endless.
Thanks Tom, this has been really helpful! Want to watch a video version of this discussion? View it here.
Tom has explained just a few of the key features of robotics cable design. If you have additional and/or special requirements for your project, Contact Us! We have provided custom cable to the robotics industry for decades. Our expert team of design engineers work closely with each customer to develop innovative, one-of-a-kind wire and cable solutions.
Today, we speak with Clayton Elliott, Design Engineering Manager here at New England Wire, about some of the specific design considerations and materials that go into today’s Ventilator Cables and their importance.
Q: Thanks for taking some time today to answer a few questions, Clayton…We know the medical industry requires some of the most high-performance, specialized products in the world. Where does the ventilator cable stand in terms of complexity of design and construction?
A (Clayton): While the standard ventilator cable may not be as complex as some of the highly specialized solutions we provide, it is nonetheless a critical component in the device and needs to retain physical and performance characteristics over the long term, under some pretty harsh conditions.
Q: In your opinion, what are some of the most important performance characteristics of this particular cable?
A (Clayton): Well, as I mentioned, they definitely need to stand up to potential abuse given the environment, but beyond that, there are some other considerations such as interconnection capability and shielding requirements that need to be taken into account.
Q: You mentioned the harsh conditions and physical construction, can you talk about that a bit more?
A (Clayton): Yes, well in terms of durability, the jacket plastics need to be selected not only for wear and tear, but for comfort and ease of cleaning. Medical cables in general are constantly being coiled and uncoiled, stepped on, and rolled over. Repeated sterilization in harsh conditions can further stress the cable’s physical and electrical integrity. Choosing the appropriate jacket material is critical to meet the performance demands of biocompatibility, disinfection and sterilization compatibility, environmental regulatory compliance, aesthetics, flexibility, durability, and cost. Additional surface finishes may be applied to some jacket plastics for reduced coefficient of friction and ease of cleaning.
Q: What do you mean by “comfort”?
A (Clayton): The useability of these cables by respiratory therapists, nurses and physicians is an important factor. By using smaller gauge size wires to create ultra flexible strands which are then paired with appropriate conductor plastics, the cables survive a larger number of bend cycles without suffering fatigue while offering the handler improved movement, flexibility, and overall ease of use. Patients may also appreciate a highly flexible cable as as it can decrease pulling and jabbing as they move around in the hospital setting.
Q: What about some of the other electrical capabilities you mentioned?
A (Clayton): Well, first and foremost is the constantly increasing interconnect demands of new devices today. Hybrid cable capability is crucial for meeting the numerous interconnects of a single device. Adding highly reliable wired USB communication cables to the overall design means more functionality and performance in the same circular cross-section. Sometimes there are other demands for signal, power, vent tubes, grounding, etc. In that case our design engineers work to create a customized hybrid cable tailored to the specific requirements of any application. The other primary consideration is proper shielding. This is essential to many applications as it can keep out unwanted external interference. In many cases, electromagnetic interference (EMI) is a threat to signal integrity. Shield quality is of particular importance in small signal or high frequency applications where a slight variation can have significant impact. All electrical cable will radiate energy to, and pick up energy from, its surroundings. As such, shielding can also be used to contain the electromagnetic energy radiated by a cable, which can protect nearby sensitive components – crucial in hospital settings where numerous electronics are in use within confined spaces.
“Thanks so much for taking the time to break it down for us, Clayton.”
These are just a few of the key features of ventilator cable design. If you have additional and/or special requirements for your project, Contact Us! We have provided custom cable to the medical electronics industry for decades. Our expert team of design engineers work closely with each customer to develop innovative, one-of-a-kind wire and cable solutions.
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Download our General Capabilities booklet here
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Download a PDF of our informational booklet specific to Medical Cables and learn about New England Wire’s unique products and services we offer to support the medical device industry.
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While it is often one of the last characteristics mentioned, flexibility is an important design consideration for many wire and cable applications. Other aspects such as number of conductors or voltage rating are essential to designing an adequate construction, however, for many multi-conductor cables, the difference between adequate and ideal comes down to flexibility.
Off-the-shelf multi-conductor cable will typically utilize solid or coarsely stranded conductors, stiff insulation, separation layer materials, and foil shielding to cut costs. For applications in which flexibility is not an afterthought, a custom solution is often required. New England Wire Technologies specializes in designing and manufacturing flexible multi-conductor cable tailored to your specific requirements.
Design Methods:
Typical Applications:
Advantages:
Learn more about our ultra flexible stranding options, custom flexible interconnects, and extended flex-life cables.
Primary insulations (insulations applied directly onto conductors) are generally hard insulations that will resist deformation and damage during cabling and other subsequent processing operations; this ensures a high measure of quality both for safety considerations and electrical performance.
Polyolefin – some of the least expensive plastics available in wire and cable, Olefins actually have very good electrical properties and as a result are commonly used in commodity signal wires such as USB and CAT5 Cables. Their main drawback is their high relative stiffness and low temperature rating (80°C).
PVC – The work horse of the wire and cable industry PVC is often used a primary insulation for its advantageous mechanical properties and its inherent flame resistance.
Polyester – In addition to having higher temperature ratings and lower embrittlement temperatures than many commonly used plastics, Polyester also offers improved abrasion resistance and can be extruded in walls thinner than many other materials.
Fluoropolymers – Developed as extrudable versions of PTFE all Fluoropolymers have very high temperature ratings, very low coefficients of friction, are extremely flame retardant and have excellent dielectric strength.
Silicone Rubber – Although not commonly used a primary extrusion due to its softness, Silicone Rubber is occasionally used for applications that require ultra-flexible cables.
Compounds used for jacket insulation are primarily flexible materials that are selected based on the requirements of the customer’s application.
PVC – Heavily plasticized PVC’s can offer a nice combination of flexibility and flame resistance.
Polyurethane – Due to its excellent tear strength and toughness Polyurethane is a preferred option for cables that will have to withstand mechanical abuse.
Thermoplastic Elastomer (TPE) – A blend of thermoplastic resins and thermoset rubbers TPE’s are very flexible jacket materials that still have good mechanical properties and a pleasant feel.
Silicone Rubber – An ultraflexible high temperature material, Silicone Rubber is commonly used for jacketing cables in the medical industry because of its ability to withstand autoclave. New England Wire has also developed NEWtuf® Reinforced Silicone to improve mechanical performance and offers Parylene and SLEEK™ coating to improve the surface texture of Silicone Rubber.
Polyester – A more rigid material than is commonly used in cable jackets, Polyester has excellent resistance to fluids and fuels and is highly abrasion resistant.
Fluoropolymers – Although Fluoropolymers are very stiff options for use as a jacket, their excellent chemical resistance, high temperature rating and natural resistance to fire makes them a good option for cables that will have to survive in particularly harsh environments.
