a unique audible
system: a click is
heard as a consequence of the
activation of the
the dose counter
one count only
after the effective release of the
Overall, the aim
of the project was
to limit the number
of materials as
much as possible,
while still using the
material that best
met the function of each component.
According to Allen, the components
were specified early in the design process based on their functional requirements, including stiffness, friction,
dimensional stability, and aesthetics. The
requirements led to a set of preferred
material types that were selected prior
to the first tooling, and have remained
unchanged. It hasn’t been necessary to
experiment with different materials.
Several engineering plastics were used
in the device, including polypropylene,
acrylonitrile butadiene styrene (ABS),
polycarbonate, cyclic olefin copolymer
(COC), acetyl, and polybutylene tere-
phthalate (PBT). Polypropylene is a
softer material with tactile benefits but
also has good static charge properties.
COC provides necessary moisture bar-
rier properties, as the reservoir of pow-
der has to be protected from the envi-
ronment so the powder won't absorb
moisture. ABS provides the hardness
required for some components, and also
offers good dimensional stability. Using
hardness and optical clarity. Where low
friction was an essential requirement,
acetyl, and PBT were specified.
Testing for Reliability
All aspects of the device needed to
work reliably, repeatedly, accurately,
and required extremely sensitive parts
and thorough testing. Thus, the scale
up of the device into commercial volumes required a rigorous investigation.
“Our approach has included testing
the devices across the possible range
of manufacturing variations, and then
redesigning parts to best deal with these
variations,” Allen says.
To make sure the dosing mechanism
would be accurate, the team built automated test rigs to simulate a patient
using the device, and had them cycle
through all 120 doses. “It is incredibly
important that the dose counter be fail
safe, as it would be dangerous for a
patient to have an inhaler displaying an
inaccurate number,” Allen explains.
The device is currently approved in
Europe and is in the process of seeking
FDA approval in the United States.
"All you have to
do is open, inhale,
and then close;
there is nothing
else the patient
has to do."