Miniature Seals: Good Things Come in Small Packages
Critical Polymer Solutions In Microsurgery (Staplers, Cataract Tools & More)
By Ronelle Decker (September 2021)
With the growth in older populations and chronic disorders, the need for surgical procedures is rising, among them microsurgeries—an evolving discipline of surgery that typically deals with very small structures such as blood vessels and nerves or sensitive areas such as tissue and cartilage and performed with the assistance of microscopic and special miniaturized instruments. Since precision and reliability are critical in this type of surgery, technological innovation has led to compact tools, which are enabling smaller incisions to be made, lowering risk of infection and potentially shortening recovery as well as reducing costs over traditional surgeries.
Powered, microsurgical devices is a trend that began in the early 2010s with developments in minimally invasive surgery providing the benefits of smaller incisions and more versatile solutions for surgeons, including better patient recovery times with leading OEMs in this space who were beginning to design smaller, more versatile solutions. Since then, the industry has seen a rise in miniature motors in surgical tools, pumps and ventilation equipment. The global minimally invasive surgical instruments market, leveraging laparoscopy and tiny instruments, is anticipated to grow at a CAGR of 9.85% , according to Grand View Research. Additionally, global hand-held surgical instruments will comprise U.S. $6.51 billion by 2025 at a 7.1% CAGR from 2019-2025 per Research and Markets.
When Small = Big: Miniature Seals Provide Critical Protection
Hand-operated surgical staplers are a good example of how smaller surgical devices are providing comfort during surgery, which have boosted their demand. In the past, they were often large, cumbersome and heavy, requiring a large amount of force to rotate and staple properly. Today, smaller versions of these devices are a third of the size, easily fitting in the surgeon’s hand. On top of that, they are often battery powered to allow surgeons to easily and properly apply staples with the push of a trigger, making them significantly easier to use. Since these tools must be precise, reliable and withstand over a thousand autoclave cycles, the micromotors operating the tools are placed under challenging and strenuous demands.
Seals are a critical component in these new smaller instruments that can help alleviate these operational and maintenance demands. With electronics housed within the tools, polymer seals such as Omniseal® spring-energized seals can help to protect interior circuitry from steam and cleaning extensions, preventing fluid entry into electronics and shafts with autoclaving reaching temperatures up to 149°C (300°F) along with other debris in surgical environments. A drill or stapler, for instance, may have up to six rotating shafts, each accommodating a different motion of the device. Each of these tiny shafts requires a miniature seal to protect electronics in the cleaning process.
Hand-operated surgical staplers are one critical application in the minimally invasive surgical instrument industry; others include orthopedic, ophthalmology, cardiovascular, neurosurgery and pediatric surgery. These applications would also benefit from using miniature spring-energized seals, resulting in long service life, high speed capabilities, high temperature management in overload conditions (torque or speed) as well as contact protection relating to fluids and alkaline solutions due to the strict cleaning and sterilization requirements.
The Rise of Cataract Eye Surgery
According to the Centre for Disease Control and Prevention, in 2015, around 20.5 million people in the U.S. (mainly those aged 40 years and older) suffered from cataracts, resulting in an increasing demand for cataract eye surgery and driving growth of the market during the forecast period.
About 50 years ago, the first phacoemulsification cataract surgery was performed by Charles Kelman, MD, (known as the “father of phaco”) in New York, in a four-hour procedure. Now, the phaco procedure can be completed in a matter of seconds due to a number of refinements in ultrasound systems, microsurgical incisions, and new hardware/software, which give surgeons a variety of power options, better control of fluidics, and improved chamber stability.
Phacoemulsification has become the primary method of cataract removal, resulting in a 98% success rate on all cataract surgery operations. It is a modern cataract surgery method in which the eye's internal lens is emulsified with an ultrasonic handpiece and aspirated from the eye. Aspirated fluids are replaced with irrigation of balanced salt solution to maintain the anterior eye chamber. The lens is replaced with an artificial intraocular lens (IOL).
Within the cataract removal handpiece itself are critical parts that make it even more stable such as our fluoroelastomer seals, which protect the handpiece electronics and withstand autoclave / sterilization cycles up to 1,000 cycles. They also have the following benefits:
Providing stability and control for a heavy-duty tool that is also considered disposable after 1,000 uses (a busy surgeon might perform 50 surgeries per day)
Tolerating the high speed piezoelectric vibration and micro-shuttling motion at the tip of the handpiece that is used to cut-up cataract tissue and suction
“Sizing” Up Sealing Solutions: Finding A Precision Seal
When one of our key life sciences customers started to develop microsurgical devices, a main concern was finding a seal manufacturer who could make seals small enough that would operate efficiently. While, generally, larger seals are more complex and expensive to produce, once spring-energized seals reach sizes below ¼ inch, they also become increasingly more difficult and expensive to commandeer.
While manufacturers might be able to minimize the number of miniature seals required by making design changes and making some of the components disposable, these types of devices—typically used for 50 to 100 surgeries before disposal—would still need to be autoclaved, and its electronics be protected.
Elastomer o-ring seals that rely on elasticity of the materials for sealing are often used in static applications with moderate pressure and temperature demands in life science. However, in addition to lower elasticity and tensile strength, and a less tight seal, small o-rings often do not work well in applications that involve fluid. Given the amount of friction in the rotating shaft, grease (not a good fit in surgical and other applications) is necessary to ensure lubrication of o-rings.
Spring-energized seals consist of a PTFE-based compound, PEEK, or other polymer jacket encapsulating a metallic spring energizer. OmniSeal® spring-energized seals provide a tight sealing solution with strong tensile strength even in aggressive media at extremely high and low temperatures [from -268°C (-450°F) to 316°C (600°F)] and at high speeds without the need for lubrication to help ensure a longer life. They are available in FDA compliant (Title 21 CFR §177.1550) and/or USP Class VI certified materials suited to address a variety of sterilization challenges and are ideal for high-speed, dry running applications that require long life.
Range of Solutions: A Big Leader in Small (and Large) Seal Design
With over 60 years of engineering and manufacturing sealing and polymer solutions, Omniseal Solutions’ spring-energized seals are designed in various sizes from extremely small—working well in miniature motors and ultrasonic surgical scalpels—to very large, as in the case of space fuel tanks and oil and gas ball valves. They have been used extensively in pumps and parts essential to manufacturing, engines and braking systems in automotive, applications facing extreme temperatures in oil and gas exploration, and in every space shuttle launch to date.
Specifically, in life sciences, our seals and polymers are used in chemical analyzers, HPLC/UHPLC, in vitro diagnostic systems, blood processing, portable and stationary oxygen concentrators, insulin delivery systems and surgical tools, to name a few. The majority of these are custom designed and matched with optimal materials by our business to ensure superior performance in their specific applications.
While many manufacturers may claim to provide spring-energized seals for life sciences, not all providers are alike when it comes to designing miniature seals for small surgical devices. When it comes to selecting seals in these microsurgical tools, the following are several important capabilities to consider.
1. Ability to Address Small Sizes: One of Omniseal Solutions' biggest strengths in this area is its ability to design and manufacture the smallest seals for micro instruments. Once the diameter of the seal dips below ¼ of an inch, the list of suppliers who can address this requirement drops dramatically. Our business is able to produce some of the smallest seals for these applications.
2. Options to Ensure the Best Seal for Any Application: With 100+ different jacket materials and six spring styles—including advanced pitch to cantilever, extended spring, and more—Omniseal Solutions can provide the best seal to address the specific application.
To ensure a long seal life in the past, shafts needed to be comprised of hard materials to prevent wear from jacket materials working against the soft substrates. However, hardening, plating or coating materials can become expensive, and with some instruments having up to six shafts, these costs can multiply. Our jacket materials enables equipment manufacturers to leverage any type of shaft material—including soft materials—to ensure a long life, enabling less expensive surgical devices to be created.
3. Quality Materials: Similarly, Omniseal Solutions ensures the quality of all of its materials. As an example, we use a specially formulated high-performance polymer as the jacket material for our spring-energized seals (with numerous options available). This custom material formulation is produced in-house, starting with PTFE resin sourced from leading, trusted suppliers to a tightly-controlled process for blending and compounding fillers, all within our business to ensure consistent quality, versus looking to sub-suppliers.
4. Cleanliness: Omniseal Solutions offers high levels of purity to meet stringent cleanroom standards with seals for surgical applications able to be designed in a Class 10000 Clean Room. It also offers over twenty-two FDA Compliant or USP Class VI materials and a number of sterilization resistant materials that are suitable for sealing and friction control.
5. Precision: Our business can hold tight tolerances (of + 1), even in small seals. It’s a practice requiring extreme precision, expertise and special instrumentation, including vision aids for assemblers in clean room environments.
Our customers in microsurgical devices span the U.S., Europe and Asia, with leading medical device manufacturers and a drive component manufacturer for DC micro motors as just a few examples. Omniseal Solutions works with these customers throughout co-development to help design seals for use in the surgical instrumentation.
Whether the seal’s application is static, rotary, dynamic, linear or reciprocating, or if a soft shaft, hard shaft or plated substrate is being used, Omniseal Solutions can leverage the best combination of spring styles and jacket material for any application. While many customers may recognize our business for its seals business, its capabilities go beyond that. We also offers numerous grades of Rulon® PTFE filled materials to address friction and wear-control and Meldin® thermoset polyimide and thermoplastic high purity products for use in bearings and other parts in life science applications.
With the benefits of miniaturization and only a few major surgical tool suppliers already offering these smaller, battery-powered surgical tools, the opportunities for these devices and smaller seals will only continue to rise. Omniseal Solutions is ready to help OEMs and suppliers address their biggest challenges when they do look to miniaturization and the cost-savings, maintenance and safety benefits that come with these advanced tools.
OEMs and parts suppliers are often amazed that a tiny seal can do so much! Contact us to learn how big of an impact our miniature seals can make for your application.