Medical Design Briefs - July 2022 - 26

TECHNOLOGY LEADERS Motors/Motion Control
Performance Parameters
Brush DC
Torque
Speed
Power
Efficiency
Reliability
Weight (Inertia)
Cost (low)
Cogging
Iron Core Coreless
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Brushless DC
Slotted
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Stepper
Slotless Can Stack Disk Magnet Hybrid
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Table 3 - Comparison of key performance characteristics of different motion technologies.
* Speed. The drug dictates the duration
and flow for the therapy, so the device
speed will be set. BLDC stepper motors
can meet higher speed requirements.
Brush DC motors can satisfy medium
speed requirements, whereas steppers
can handle lower speed requirements.
To increase output torque, you can add
a gearbox and thereby increase the
speed requirements on the motor by
the corresponding ratio.
* Efficiency. Biologic drug-delivery devices
rely on battery power, so an efficient
system will keep the battery size
low. Brush DC coreless and BLDC slotless
motors have a rotor-based design,
making them the optimal choices for
system efficiency.
There are several types of devices that are used to
deliver drugs. (Credit: Portescap)
* Reliability. The device has a specific
life requirement based on the number
of therapies to be delivered to
the patient. Motor life is determined
by the commutation and
bearing systems. Brush DC motors
have a mechanical commutation,
meaning the motor life is dictated
by brush wear. BLDC and stepper
motors have electrical commutation,
which provides a potentially
longer motor life. Bearings also affect
motor life, with ball bearings
providing longer life than sleeve
bearings. Motor technologies offer
both bearing versions, with some
Adding a gearbox can increase output torque, and
thus increase the speed requirements on the motor
by the corresponding ratio. (Credit: Portescap)
providing them as standard and
others requiring customization.
* Weight. Because biologic drug-delivery
devices are portable, weight can significantly
affect patient comfort. Brush DC
coreless motors are the lightest option.
* Cost. Each motor technology has a cost
profile based on its design. The device
and accompanying therapy mandate a
cost profile for market acceptance, so
engineers need to understand the cost
drivers for each motor type.
Comparing the various motor technologies
and how they function in different
drug-injection devices is a necessary part of
device design (see Table 3). Referencing a
checklist like the one above can help design
engineers assess motor options for
their impact on device cost, efficiency, and
user experience more effectively.
Partner With a Motor Supplier Early in
the Design Process
Ultra EC™ mini motor platform is a 16 ECP brushless
motor, designed specifically to provide an economic
motor solution for high-performance applications.
(Credit: Portescap)
Athlonix™ DCP high-power-density brush DC mini
motors feature an energy-efficient coreless design.
(Credit: Portescap)
As biologic drug treatments continue
to increase in the market, each application
presents its own challenge in
terms of biologic therapy requirements.
Connecting with a motor supplier
early in the development process
can help designers and manufacturers
identify the best motor technology and
accessories to create an optimal drugdelivery
device.
This article was written by Jigar Fulia, Divisional
Manager, Product Design and Development,
and Kanti Vala, Research and Development
Manager, Product Design and Development,
Portescap, West Chester, PA. For more information,
visit http://info.hotims.com/82323-346.
26
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Medical Design Briefs, July 2022
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Medical Design Briefs - July 2022

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