The introduction of endoscopy in surgical practice is one of the greatest success stories in the history of medicine, and there is no end in sight in terms of the development of minimally invasive surgical procedures and instruments. Advances in material sciences, imaging, sensors, and robotics are driving a need for new innovative approaches to manufacturing the next generation of surgical instruments.
Minimally invasive surgery has become a routine procedure, often performed on an outpatient basis, that helps to reduce care costs, recovery times, and post-operative complications. Typical minimally invasive surgeries involve a variety of specialized endoscopes, cameras, light sources, video monitors, insufflators, trocars, and other instruments.
Robot-assisted surgery (RAS) represents the next generation of minimally invasive surgery, developed to overcome the limitations of current minimally invasive techniques and to help surgeons improve the precision of open surgeries. With the help of artificial intelligence and advanced diagnostic imaging from CT, PET, MRI, and nuclear scans, surgeons can now leverage ever-improving RAS systems to achieve significantly greater surgical precision and accuracy.
Driven by the expanded adoption of RAS systems, the next-generation minimally invasive instruments are being rapidly redesigned or adapted for robotic use. While the functional requirements of these instruments remain essentially the same, their form factors change significantly when mounted directly to robot arms. Instead of receiving haptics inputs from a surgeon’s hand through an ergonomic grip, these next-generation instruments — now called effectors — are guided electronically. They use a combination of advanced scanning and/or positioning inputs from computerized robot controls to orient themselves according to a predesigned surgical plan. Then, a surgeon can make fine adjustments using a robotic joystick, guiding the instrument using visual inputs from effector-mounted cameras. Details of the surgical plan may also be reviewed in real time, allowing the surgeon to make adjustments based on the patient’s anatomy (e.g., the angle of a new implant during a hip or knee replacement procedure).
Thanks to miniaturization and electronics, RAS effectors are generally smaller and lighter and often incorporate multiple functions compared to their endoscopic predecessors. For example, while many older surgical instruments are manufactured in a straightline configuration — which means they must bend to reach around obstructions in surgery — RAS effectors often add pre-curved or flexible sections that allow the instrument to bend around tighter corners. Many of these effectors are electromechanical, with designs that incorporate a range of materials, including metals, elastomers, and high-performance plastics.
However, the ever-smaller sizes, complex shapes, and sophisticated electronics, communications, and controls required to guide and direct effectors — along with uncompromising global standards for medical device safety, reliability, and quality — pose major manufacturing and assembly challenges for medical device manufacturers.
Addressing Assembly Challenges
Fortunately, assembly technologies continue to evolve as well. For RAS systems and end effectors that incorporate metal, elastomeric, and plastic components, ultrasonic welding remains a core manufacturing technology. Basically, ultrasonic welding bonds compatible materials through a combination of vibratory motion and compressive force. Mating surfaces of two parts are compressed together then subjected to high-frequency oscillation that creates mechanical friction — and heat — on those mating surfaces.
In the case of plastics, ultrasonic welding creates a small, but controlled, melt area in the weld joint between the two parts. Recent advances in this process make it possible not only to control the time, depth, and power inputs to a weld but also to regulate downforce so that parts containing sensors and electronics, or parts with extremely close tolerance joints (for example, RAS effectors, cameras, and related components), can be welded successfully. Often, ultrasonic plastic welding is employed for assembling housings and components that contain motors, sensors, cameras, valves, or small-scale tubes that transport and manage critical fluid or gas flows used in the surgical procedure.
In the case of nonferrous metals (e.g., copper, aluminum, nickel, silver), ultrasonic welding employs vibration and compression to create a solid-state molecular bond between metal parts. The metallic bond is unique to ultrasonic metal welding. Another key advantage of metal welding is the elimination of health issues associated with soldering fumes, reducing the need for certified soldering stations, and improving process throughput quality and repeatability by utilizing the process logic and data capture capability of the ultrasonic splicing systems.
Unlike other welding processes, the process heats but does not melt the metal parts, and therefore does not produce the intermetallic compounds that can lead to eventual corrosion. Ultrasonic metal welding is also used to create tab and foil circuits that are essential to energy storage or batteries. These batteries transmit power to motorized or heated components and communicate visual data, control signals or telemetry essential to visualize, and control robot arms and effector functions. Another key application is for electrical connections of fine wire assemblies, e.g., 30 AWG Ag (silver) coated Cu (copper) stranded wire to a single point contact for a sensor or actuator.
Both processes — ultrasonic plastic and metal welding — also bond without the need for additives or consumables. So, in the case of robotic arms or surgical end-effectors made of biocompatible plastics, component welding does not introduce the risk of external contaminants. Both processes can also bond extraordinarily small, fragile, or thin components. Also, because ultrasonic processes are so rapid, energy efficient and repeatable in quality, it is possible to fabricate high-quality, disposable end effectors for RAS at a very predictable and affordable cost.
Laser plastic welding is a third assembly process relevant to the production of medical robots and end effectors. This process is used to ensure the gentle, flash- and particulate-free bonding of plastics used in Class A aesthetic surfaces, which include the exterior surfaces of surgical robots, arms, and effectors. Laser welding is accomplished by transmitting a laser heat source through a transmissive plastic part and into a laser absorbative plastic part, which softens and begins to melt, enabling the two parts to be joined under gentle compressive force. Other benefits of laser welding include hermetic sealing between parts; the ability to join extremely thin or fragile parts; and the ability to trace extremely fine weld lines, which are essential to joining parts with narrow or microfluidic flow paths.
Another process essential to the production of surgical devices, RAS effectors, and even surgical implants is precision ultrasonic cleaning. This method uses an ultrasonic generator to produce high-frequency energy pulses in aqueous or solvent cleaning solutions in which manufactured components are immersed. The ultrasonic pulses produce cavitation, or fine bubbles that function to remove manufacturing process contaminants from product surfaces.
Improved Patient Outcomes
Together, assembly technologies like these — ultrasonic plastic and metal welding, laser plastic welding, and precision ultrasonic cleaning — are helping to shape the future of RAS systems and instruments. They help solve a wide range of assembly challenges and give device designers a new degree of freedom to explore innovative manufacturing methods that can shorten development times. For example, additive manufacturing processes using 3D printed tooling can rapidly prove out a tooling concept, optimizing the design in days rather than weeks.
The experience of technology providers in developing minimally invasive surgical instruments and RAS systems assembly offers significant advantages for the leading manufacturers of robot-assisted surgical systems. Adapting minimally invasive surgical instruments for end-of-arm robotic use will no doubt lead to improved patient outcomes.