Medical Design Briefs - July 2022 - 25

TECHNOLOGY LEADERS Topic
force density within the smallest available
size.
Current Challenges in Biologic DrugDelivery
Systems
Like biologic drugs, biologic delivery
devices are relatively new to the market
and are continuously improving. Because
biologics are more complex with higher
molecular weights and viscosities than
small-molecule chemical drugs, biologic
drug devices face the following challenges:
* Accommodate high-viscosity drugs.
* Deliver a large volume of a drug.
* Delivery accuracy.
* Cost optimization in order to reach a
larger population.
Some of these challenges can be supported
by motor-driven systems (see Table
2):
* Brushless and brushed motors have
higher power densities, which, in combination
with higher reduction ratio
gearheads, can handle high-viscous
drugs greater than 50 cP.
* Power density helps to accommodate
larger drug volumes in a smaller device
size, ranging from 10 to 50 mm.
* Absolute encoders can help precisely
monitor drug delivery at 3-5 µm
resolution.
* Reliable motors and gearheads provide
long life for safe, home-based therapies.
Motor and Gearhead Options for Biologic
Drug-Delivery Devices
Because powering the delivery mechanism
is a crucial part of a drug-delivery
device, design engineers must evaluate a
variety of motors and gearheads to find
the most appropriate component for
their application. To complete this selection
process effectively, engineers can
consider the following list of key performance
elements of drug-delivery devices
and the different motor technologies
that can handle them:
* Torque/power. All motor technologies
offer the ability to produce torque, but
their internal designs present different
output capabilities. BLDC slotted designs
deliver higher output torque
than BLDC slotless designs, based on
the higher amount of copper and magnets
in the motor. When considering
stepper motors, hybrids provide the
highest torque.
Medical Design Briefs, July 2022
Biologics are drugs made of proteins and/or derivatives that modulate the immune system. (Credit: Portescap)
Biologic Drug Device Parameters
Device lifetime
Packaging
Battery operating time (hrs)
Ability to handle drugs
Drug cartridge capacity (mL)
Driving unit of device
Needle system (patch type)
Refrigeration
Sterlization
Disposable Applications
+
+
+
Specific drug
~3
Disposable
Automated insertion
and retraction
Not applicable
Not applicable
Limited-Use Applications
++
+
++
Specific drug
3-10
Separate from
disposable unit
Automated insertion
and retraction
Possible
Not applicable
Table 1 - Key performance characteristics for different biologic drug-delivery devices.
Motion Solution Parameters
Drive Technologies
Performance (Torque/Force)
Performance (Force), N
Output linear speed
Efficiency
Input voltage , V DC
Encoder needs, LPR
Weight
Size/Packaging
Life
Reliablity
Disposable Applications
Stepper/Brush DC/Others/
Mechanical
Limited range
Up to 50
1-3 mL dispensing
in <10-100 seconds
+
1.5-3.6
1-16 lines
+
++
+
+++
Limited-Use Applications
Stepper/Brush DC
Limited range
Up to 120
Up to 10 mL in up
to 20 minutes
++
3.6-7.2
1-16 lines
+
++
++
+++
Reusable Applications
Brush DC/BLDC
Wide range
torque/Force
Up to 200
Up to 10 mL in up to
2 to 4 hours
+++
3.6-7.2
16-128 lines
++
++
++++
++++
Table 2 - Technologies and key performance characteristics of motor-driven systems used for biologic
drug-delivery devices.
Reusable Applications
++++
++
+++
Various drugs based
on viscosity
3-10
Separate from
disposable unit
Automated insertion
and retraction
Possible
Possible (based
on design)
www.medicaldesignbriefs.com
25

http://www.medicaldesignbriefs.com

Medical Design Briefs - July 2022

Table of Contents for the Digital Edition of Medical Design Briefs - July 2022