Medical Design Briefs - June 2022 - 11

Another shortcoming is the elaborate
handling of high-volume and viscous
formulations that conventional drugdelivery
devices are not capable of.
Some new drugs require specifi c dose
timing concerning starting time or fl ow
rate, while others are in a lyophilized
state and require reconstitution. To
overcome these administration-related
challenges, new drug-delivery mechanisms
are required.
Connected Large-Volume Injectors
For a few years already, large-volume
injectors (LVIs) - also called on-body
delivery systems, patch pumps, or wearable
drug-delivery devices - have been replacing
intravenous infusion with subcutaneous
injection. They are less painful to
apply and enable chronic disorders to be
treated at home by patients themselves.
In particular, prefi lled drug-device combinations
provide a convenient and reliable
alternative to outpatient treatment.
Because of the high volumes and
viscosities, biopharmaceutical delivery
must be controlled, confi rmed, and
tracked. Automatic drug-delivery systems
with fl ow rates ranging from 1.5 to
300 ml per hour ensure continuous drug
delivery out of a vial over a specifi c period
of time. LVIs can also allow lyophilized
drugs that need be delivered by
the user shortly after reconstitution to be
fi lled at the point of use.
Challenging Device Design
The market for LVIs for non-insulin
drugs is expected to grow at fast pace in
this decade. Over 50 wearable products
and more than 10 drug-device combinations
with high storage capacities are
either commercialized or in development.
Whether selling devices including
a medication or not, the drugdelivery
industry is facing many design
challenges: improving the handling of
viscous formulations and optimizing usability
as well as keeping devices small
and costs low.
Consequently, most LVIs are made of
disposable and reusable parts, which
makes sense in environmental terms.
Although the battery, motor, readout
electronics, connectivity module, and
display are reusable, the needle, drug
compartment, patch, and wetted sensors
are disposable.
As recent events have shown, LVIs can
also be designed for already existing
Medical Design Briefs, June 2022
Cov
MDB Sensirion Sensors Feature 0622_1.indd 11
TEST DESIGN
The lightweight in-line pump
CS-3 with barbed inlet and
outlet connectors for easy
fi tting to tubing is designed for
precise microdosing at fl ow
rates of up to 100 ml per hour.
Taking up only 0.5 cm3
app, but additionally enable communication
such as telemetry with stakeholders
involved in the patient's care, like
family members, parents, or relatives.
Nursing staff, doctors, pharmaceutical
companies (for research), and health
insurers (for proof) receive updates as
well as metrics about the administration
and the device status.
of space
(12 × 6 mm), the liquid fl ow
sensor offers millisecond-fast
response times as well as both
direct and bidirectional fl ow rate
measurement.
drugs. Although a patent on a drug expires
(Amgen's Neulasta in 2015, for example),
the availability of a new on-body
injector can lead to an extension of the
drug's lifetime and the related business
for Amgen. Thus, new life-cycle management
strategies in the pharmaceutical
and medical industry can create new revenue
streams.
Miniaturized, Cost-Effective, and
Disposable Sensors
Since there are various biopharmaceuticals
with different properties, LVI
designers must individually guarantee
reliable, precise function and high
ease of use. Up to now, they equipped
devices with visual, audio, or tactile indicators
for needle positioning and onbody
attachment. Even failures like occlusions
can be detected to some
degree, but currently only in an indirect
way, leaving the possibility of false
positives.
Even more important is the direct fl ow
measurement and delivered volumes as
well as bidirectional measurement capability,
which conventional sensors are
not capable of. Sensirion's sensor solutions,
for example, allow miniaturized,
disposable liquid fl ow sensors to be integrated
into LVIs to control, confi rm, and
track subcutaneous drug delivery in real
time. They enable precise dosing in
terms of fl ow rate as well as administered
volume and enable automatic failure detection
such as occlusion or air-in-line in
a cost-effective and direct manner.
Integrated into a connected LVI,
these next-generation sensors not only
allow the administration to be monitored
by the patient via a smartphone
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Programmable features could also
adapt or optimize the subcutaneous
drug-delivery process. In case an injection
device shows issues, a fl ow sensor
can provide peace of mind to patients as
well as their relatives. Put simply: implementing
a tiny smart sensor improves
therapy outcome, patient adherence,
and quality of life. Miniaturized liq uid
fl ow sensors address the abovementioned
market trends and provide a
great value-to-cost ratio.
Sensor, Pump, and Beyond
Finally, in designing LVIs, it is recommended
to view the liquid fl ow sensor
and the pumping mechanism from a holistic
point of view. To identify the ideal
design of the fl ow control system in
terms of size, performance, ease of integration,
manufacturability,
and
cost,
medical device manufacturers should
aim for the best possible combination.
Conventionally, pump technology is
selected fi rst and often independently
of the fl ow sensor, especially when
unique requirements and related intellectual
property of the device manufacturer
are involved. Combining a previously
selected pump with a liquid fl ow
sensor can be challenging, especially
when the pump performance requires
further improvement, failure detection
and resilience, all to be provided by the
sensor. The pump's specifi c working
principle, fl ow profi le, mechanical design,
and fl uidic connectors might further
complicate the task.
In one application, for example,
Sensirion assembled a small-footprint
liquid fl ow sensor with a single-use micropump
from Quantex Arc. The result
was a highly compact fl ow controller
providing a steady fl ow in different
fl ow regimes and consuming very little
energy.
This article was written by Andreas Alt,
Sales Director, and Susanne Pianezzi,
Business Development Manager, Sensirion,
Stäfa, Switzerland. For more information,
visit http://info.hotims.com/82322-341.
11
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Medical Design Briefs - June 2022

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