Axsis has the potential to transform a range of procedures, creating opportunities to use robots in completely new areas of surgery.
Flexible instruments and a novel motor / control configuration result in an external body no bigger than a drinks can.
Driving a 1.8mm arm with a 1mm working channel, Axsis combines four-degrees-of-freedom motion with the ability to apply multi-directional forces – axial, tangential and grasping – without any external motion.
Operating space efficiency
Designed to work within the constraints of real-world operating rooms, Axsis can easily be deployed for part of a procedure and quickly removed for unhindered access to the patient.
The flexure’s rolling curve profile ensures a smooth and efficient motion that mirrors the surgeon’s hand movements. Force-reflecting telemanipulation gives the surgeon tactile feedback and a true sense of touch.
Axsis integrates with real-time 3D imaging, enabling a new level of robotic assistance. Virtual boundaries, surgical ‘macros’ and integration of artificial intelligence (AI) to inform and aid surgery all become possible.
Our objective – to develop a lightweight, compact robot – is something that many others have tried before. However, by starting with a strong fundamental understanding of clinical practise and by making procedural priorities and clinical objectives our driver, we rapidly focused in on a design approach that varied from the norm.
Rather than try to shrink traditional robotic design approaches to work on a smaller scale, we took a different route – developing a core design that was small while delivering the right combination of functionality. Early proof-of-principle prototyping gave us confidence in our approach and allowed us to identify key technical challenges to be addressed early in development.
Once our core concept was established, we moved on to rapid development of the final system. Taking approximately five months from concept to demonstrator, our risk-based and systems engineering-led approach allowed our teams to run fast in parallel, with confidence that the system would integrate and work as expected, first time.
Seeing the potential
Cataract lens replacement is the highest volume surgical procedure in the world, with more than 300,000 operations carried out by the NHS in the UK every year. Outcomes are generally very good, but in some cases the patient is left with worse vision than before.
The surgery is currently performed by hand under a microscope. We realised that, if we could build a surgical robot on a miniature scale, the established benefits of robotics – such as motion scaling and minimally invasive access – could improve outcomes and allow more facilities to offer the procedure.
The scale of the problem
Our surgical robotics team worked with practising surgeons to understand the challenges of adopting current-generation robots for ophthalmology. Large by design, these robots feature long, straight instruments passing through small openings in the patient, driven by large, load-bearing motors. Consequently, these robots are simply not suitable for ophthalmological applications.
Our design uses small, static, non-load-bearing motors, rolling joints and a novel transmission system to minimise friction. The result is a fully articulating robot designed to operate on a completely different scale to traditional surgical robotics.
A big future
Having developed Axsis as a technical demonstration for ophthalmic surgery, we are now looking to the possibilities beyond.
Miniature, articulating surgical tools have the potential to deliver significant benefits in many other areas, such as early intervention procedures for cancer and natural orifice surgery for oesophageal and gastrointestinal tract procedures, as well as the placement of certain neurostimulation implants.
Tales of the team
“The parallel mechanism design enables the use of high-performance miniature linear actuators, providing high power density and integrated sensing.”
Ben Lefroy, mechanical design
“The stainless steel, rolling link end-effector design achieves axial stiffness, low-friction movement, tight radius of curvature and manufacturability.”
Chris Wagner, technical authority
"By rethinking the traditional approach to the design of surgical robots, we came up with a kinematic design that enabled us to fit all components into a body just 56mm in diameter."
Rodrigo Zapiain, lead mechanical engineer
"Working on the membranes within the eye is precise and delicate work that has a significant impact on a patient's quality of life. So assembling 1.8mm links with cables of 0.08mm in a robust way was essential for control and flexibility."
Jayna Jogia, manufacture & mechanical design
“We found an interesting solution for maintaining cable tension throughout the range of motion, using a numerically optimized 2D gimbal to compensate for the non-linear cable stretches.”
Erica Kantor, mechanical design
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