More, NEXThaler is
characterized by a unique
feedback system: a click
is heard as a consequence
of the activation of the
and the dose counter decrements by one count only
after the effective release of
Materials for Functionality
Overall, the aim in designing
the NEXThaler was to limit
the number of materials as
much as possible, while still
using the material that best
meets the function of each
According to Allen, the
components were specified early in the design
process based on their
including stiffness, friction, dimensional stability, aesthetics, etc. The requirements led to a set of preferred material types that were selected prior to the
first tooling round, and have remained unchanged. It hasn’t been necessary to
experiment with different materials.
Several engineering plastic materials were used in the device including polypropylene, acrylonitrile butadiene styrene (ABS), polycarbonate, cyclic olefin
copolymer (COC), acetyl, and polybutylene terephthalate (PBT). Polypropylene provides a softer material with tactile benefits but also has good static
charge properties. COC provides moisture barrier properties as the reservoir of
powder had to be protected from environment so the powder wouldn’t absorb
moisture. ABS provides the hardness required for some components and also
offers good dimensional stability. Polycarbonate gives good dimensional stability, but also hardness and optical clarity. When low friction was an essential
requirement, acetyl and PBT were specified.
Testing for Reliability
All aspects of the device needed to work reliably, repeatedly, and accurately,
and also 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 this
variation,” 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.
Several engineering plastic materials were used
in the device including polypropylene, acrylonitrile
butadiene styrene (ABS), polycarbonate, cyclic olefin
copolymer (COC), acetyl, and polybutylene terephthalate (PBT).