Actuonix

At a Glance

• Linear actuators provide controlled movement to joints and muscles during recovery from fractures, sprains, and atrophy.
• Linear motion is a common requirement in a wide range of medical devices.
• Linear actuators are used in infusion pumps and IV drips to deliver precise doses of medications.

Actuators are used in a variety of medical applications ranging from prosthetics through to testing and rehabilitations devices. Actuonix’s medical clients range from startups through multinational medical device manufacturers.

There are several benefits of using micro linear actuators when developing medical devices. They save engineers the difficulty of designing a bespoke linear motion solution using motors, slide rails, lead screws, and other parts. The actuators free up time for engineers to work on other important aspects of product design.

Actuators are also relatively easy to access in high volumes when required. They can alter input, speed, force, and other factors without the need to completely redesign the system. Plus, they are affordable, relative to designing a custom motion solution.

Actuonix Motion Devices provides micro motion solutions for several markets including robotics, aerospace, automotive, medical, and radio control. This article looks at Actuonix actuators that are designed for the medical sector.

We caught up with Owen Hubner, electronics engineer at Actuonix, to get more details about how to build medical devices using actuators.

Explain some of the uses of linear actuators in medical devices.

Owen Hubner: Linear actuators are growing in demand in the medical sector owing to their ability to provide precise and controlled linear movement on smaller and smaller scales. We are seeing more and more aspects of patient care gain assistance from automation and robotics – from rehabilitation to surgery – and linear actuators power many of these dynamic systems. 

Some examples of systems we see leveraging linear actuators include:

Physiotherapy/rehabilitation – Linear actuators are placed in specially designed devices to provide controlled movement to joints and muscles, aiding patients in recovery from ailments like fractures, sprains, and atrophy.

Prosthetics – Some linear actuators are small and powerful enough to be built into prosthetic hands and other extremities, providing precise movement of individual digits and joints while providing enough force to lift objects and perform day-to-day tasks with lifelike movements. 

Infusion pumps & IV drips – The precise position control of linear actuators is used in infusion pumps and IV drips to deliver precise doses of medications and to tightly regulate the flow of IV fluids to patients. 

Imaging/scanning equipment – On a larger scale, linear actuators can control the positioning of both the patient and scanning equipment for procedures like MRI and CT scans. Here, both power and precision movement are essential to ensure both the patient and equipment are held in the correct position throughout the whole procedure.

What are the advantages of using linear actuators compared to a bespoke linear motion solution?

Owen Hubner: The main advantage of using a linear actuator is basically that the manufacturer of said actuator has already put in the time and effort to design a product that is as compact, high-performing, and low-cost as possible.

Linear actuators consist of many moving parts and specialized components and considerable amounts of time designing and prototyping are required to get them working together to deliver good performance and reliability. Some highly specialized systems may warrant a fully bespoke linear motion design, but I’d suggest designers always check fist to see if their requirements can be met by an off-the-shelf solution that could save you both time and money.

How can the use of actuators reduce costs in designing medical devices?

Owen Hubner: The development of medical devices is a long process of designing, prototyping, and testing before it can go to market. Because of the intense engineering and time involved, medical devices are an extremely costly investment and certain off-the-shelf products can help offset that cost.

Linear motion of some kind or another is a common requirement in a wide range of devices from prosthetics, to infusion pumps, to imaging and body scanners. Linear actuators can help meet those requirements while saving on design time and getting a product to market faster. 

How do design engineers determine which actuator is best for a piece of medical equipment?

Owen Hubner: Design engineers have many factors to consider when designing an actuator into a piece of medical equipment. 

There are several performance-related factors:

Force – One of the most fundamental questions is ensuring the actuator in question can drive the load under which it is expected to operate. Overloading the actuator may result in a loss of performance, decreased lifespan, or damage to drive mechanism. One must therefore make sure that the maximum expected load falls within the actuator’s rated specification.

Control method – Designers are often working to integrate the actuator with a predetermined control interface. For actuators with electric motors, this might be directly driving the motor in & out or controlling the actuator speed or position using a control signal like a PWM voltage signal.

Voltage/power – Many designs are also constrained by what power rating and voltages are available to use to power the actuator. It is critical to make sure the actuator’s rated voltage and current draw match what your system can provide.

There are also several physical characteristics:

Stroke length – Most models of linear actuator have a wide selection of stroke lengths available. When selecting for a certain model, you should make sure it is available in a stroke length that suits your design. Some actuator manufacturers will even do custom lengths at higher volumes.

Rod vs. track actuator – Rod-style and track-style have different pros and cons and are suited for different applications. Rod actuators consist of a shaft that extends from the housing and are best suited in applications where the load is already supported along its axis of movement. Their design often makes them simpler to mount to the load than track actuators, but they are vulnerable to wear/damage if heavy side-loads are put on the actuator shaft.

Track actuators cover this weakness with a linear guide or track to which you mount the load.  The lack of an extending shaft also makes their total footprint less than that of a rod-style actuator.

Article source: MDDI