Medical Design Briefs - November 2023 - 15

hospitals, physicians' offices, clinics, pharmacies
and even patients' homes. Advantages
of POCT include reduced complexity,
rapid results, cost- effectiveness,
accessibility, improved
nience, and reduced patient risk.
POCT instruments often use similar
assays (testing procedures) as the central
labs' traditional instruments, but the
POCT instruments are typically much
smaller and easier to use. Ease of use is
critical, since POCT instruments will be
operated by people with widely varying
levels of experience and training. In addition,
POCT devices must be designed
to perform similar process steps as central
lab machines but must do so within a
much smaller footprint. This design
challenge has been met by reducing the
volumes of biological samples and reagents
needed to perform the assays,
and by reducing the fluid handling requirements
in the instrument down to
microfluidic levels.
POCT instrument developers who employ
solenoid valve technology to conMedical
Design Briefs, November 2023
patient convetrol
the flow of fluids in their products
can design the fluidic path to flow directly
through an isolation valve or, alternatively,
employ a general-service (air) solenoid
valve as part of a microfluidic
system design.
An isolation valve provides hermetic
separation of the control mechanism and
the fluid. If choosing an isolation valve, a
designer should look for several critical
characteristics. First, it must have a small
footprint to reduce overall instrument
size. Second, it must be able to operate
with a very low internal volume, to allow
for small sample sizes and low reagent
consumption. Finally, power- saving features
such as a latching coil or an integrated
hit-and-hold circuit reduce power
consumption and therefore reduce the
potential for heat generation, which is
important when a valve is processing with
thermally sensitive samples.
As clinical diagnostic instruments get
smaller and closer to the patient, new designs
are increasingly moving away from
traditional fluidic systems and toward
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utilizing microfluidics.
To ensure
that assays are conducted
properly (without the presence of highly
trained lab personnel), these designs
often rely upon single-use microfluidic
cartridges that are preloaded with the
reagents needed to perform the assay. In
POCT systems with this type of fluidic
design, general-service (air) valves can
be used to pilot or drive the mechanism
that generates the movement of fluids
(reagents, samples, etc.) within the cartridge
and the POCT system in the proper
sequence. Among the key features to
consider in a general-service valve for
POCT applications are 1) ensuring a
high size-to-flow
ratio, 2) minimizing
weight, 3) high cycle life, and 4) low
power consumption.
Home-Use Medical Devices
A home-use medical device is intended
for use outside of a professional
healthcare facility, such as in a home.
The user can be the patient, a caregiver,
15
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Medical Design Briefs - November 2023

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