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Micro Servo Gear Motor for Single-Use Medical Device

Precision Servo Motors for Medical Devices

There has been a growing trend amongst electronic medical device manufacturers to make both single-use and reusable devices more portable. As electronic medical devices become more compact, the components inside of them need to shrink as well. When designing a device intended for use in the medical or healthcare industry, precision is mandatory.  Some examples of electronic single-patient or disposable medical devices are surgical tools, syringe pumps, endoscopic tools, and ventilators.

With the improvements to Lithium Ion battery technology, the limits imposed by power cords are a thing of the past. Smaller, lighter, and more portable devices are flooding the medical market. With use in both laboratories and field studies, the precise control offered by motorized medical devices has become a necessary part of the modern medical professional toolkit. At the heart of these devices are micro motors, steppers and mini servo motors.

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This project involved working with a design and manufacturing company that aimed to launch a precision medical single-use device. They had less than a year to get fully functioning models into the field for FDA evaluations. Our customer was looking for a micro servo motor, essentially a spur gear motor with an encoder, to drive the internal mechanisms of their medical dispensing device. They presented us with a unique set of performance requirements and tight tolerances, making this project unique and a welcomed challenge.


Due to the nature of the application and how the device operated, the customer needed an electric motor to operate over a wide range of input voltages, hitting numerous torque and speed requirements throughout. Our gear motor had to have an operating voltage of less than 7VDC, but have a minimum starting voltage of just over 1VDC. The device is battery operated so current draw was also a constraint we had to consider.

In addition to the gear motor, they also needed a precise encoder to control dispensing flow rates, but the overall diameter of the gear motor was less than 12mm. The position control of the gear box output shaft and connected lead screw was critical to the functionality of this device. The encoder not only had to provide high resolution, but the waveform had to be extremely consistent. At first glance, we thought our preexisting magnetic encoder would be a good fit for the application. However, our existing encoder was not capable of the fine resolution and precision our customer required.

The main reason this customer reached out to ISL was because other suppliers were not able to offer a viable solution, in their requested form factor. Additionally, there were growing concerns of quality with other suppliers and since this was a medical device, quality and consistency was the utmost important aspect. Our customer had requested each gear motor have a unique serial number and wave form data collected during final quality inspection.


Our team of engineers chose to start with one of our more common spur gear motor designs that met the size constraints.

We then had to consider the varying operating conditions and electrical demands. After extensive R&D we decided to adjust the internal windings of the motor so that our servo motor was able to deliver the upfront torque and power required, while also being energy efficient.

We then had to adjust the reduction ratio of the spur gearbox to provide optimal performance. We decided to use a high speed dc motor coupled with a high reduction spur gearbox to achieve the performance needed. By converting the motors speed into torque through the gearbox, we hit both the high torque and low speed our customer tasked us with.

Once our gear motor solution proved to meet all of the torque and speed requirements we turned our attention to the encoder. For the encoder design, we opted to go with a dual channel magnetic encoder that utilizes hall-effect sensors for precise feedback. The customer then designed their motor controller to communicate with and interrupt feedback from our high resolution encoder. In order to increase the encoder resolution we designed and integrated a higher pole-count magnetic ring. This in turn doubled the encoder resolution. The high resolution encoder coupled with the high reduction of the gearbox provides exceptional positioning and control.

In order to keep the encoder phase shift consistent, we created custom encoder assembly fixtures to ensure that each encoder PCB was designed and installed consistently onto each motor. Through the use of SMT technology, all PCBs had limited variances. To meet our customers’ quality and consistency requests, we contracted a third party equipment designer to design and build us a custom encoder inspection machine. This machine measures and records each encoder’s performance during our final QC process. It provides our QC team with a quick determination of the encoder accuracy. The data is then exported into a report and sent with each shipment to our customer.


Working with product development teams can be a balancing act of trying to meet an application’s performance requirements while working with constrained space and a finite budget.

At ISL Products our mission is to deliver tailored components that uniquely suit our clients applications. After months of testing, validation, and calibration, we were able to provide our customer with a truly bespoke micro servo motor solution for their precision instrument.

With decades of experience designing and manufacturing servo motors and micro servo motors, ISL Products knows what it takes to get precision in a small form factor. The utilization of high quality materials, manufacturing techniques and encoders all help achieve what medical device manufacturers expect from the optimal servo motor solution.

Our team stayed in constant communication with the customers R&D team, providing updates, timelines, and performance data to keep them not only in the loop, but intimately informed. Our collaborative approach resulted in many design updates before a finalized product was delivered to the customer. In this time we worked through use cases that hadn’t been planned yet and enhanced our components to further the success and influence of the application.

Contact ISL Products today to create the ideal motor solution for you!

Samples of a similar gear motor can be found on DigiKey: