---
title: Quattrii Clinical — The Ugly Duckling Stage
description: Explore the development of Quattrii Clinical inhalers, focusing on aerosol performance, engineering challenges, and the importance of reliable testing in clinical settings.
image: https://chi.uk/hubfs/Sygnet.png
---
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[David Harris](https://chi.uk/chi-blog/author/david-harris)Oct 21, 2026, 3:08:26 PM4 min read
# Quattrii Clinical — The Ugly Duckling Stage
[Previous](https://chi.uk/chi-blog/inhaled-biologics-devices-and-testing-must-keep-pace)
Quattrii Clinical looks like an inhaler developed by people who are unusually interested in what air does inside small holes, which is a reasonably accurate description of us. We have spent a great deal of time on the aerosolisation engine, the blister and the way the two interact, and considerably less on making the casing handsome. At this stage, we are quite comfortable with the resulting ugly duckling.
These devices are intended for pharmaceutical evaluation and early clinical studies. They need to handle the right primary package, pierce it correctly and reproduce the airflow conditions on which aerosol performance depends. They also have to assemble reliably and be straightforward to use in the intended clinical setting. That is enough to keep us occupied before anyone starts asking whether the mouthpiece could have a more elegant curve…
An attractive CAD rendering can acquire a surprising amount of authority early in a project. Once the external shape is established, the engineering team can find itself trying to fit the required airflow geometry into whatever space is left. In a DPI, a small change to an inlet or passage can affect how energy reaches the formulation, so we want enough freedom to understand those relationships before fixing the product around them.
*The two Quattrii Clinical formats shown in hand, illustrating their small size.*
Much of that work is done using high-resolution SLA parts, which let us alter dimensions and test the resulting aerosol without commissioning a new mould tool every time we learn something new. We are already designing for injection moulding, including draft angles, wall geometry and tooling considerations in the components we print. We want the development data to describe something we can eventually make.
> An attractive CAD rendering can acquire a surprising amount of authority early in a project.
Surface finish and small airflow holes can make this work a little less convenient than simply pressing ‘print’. Where finish affects the airflow, we can bead blast or polish the SLA component to make it more representative of the moulded part. Some features are printed with additional sacrificial material which we subsequently remove, allowing us to finish them back to the nominal geometry. Small holes can also be machined or carefully reamed after printing, so that printer resolution has as little influence as practicable on the aerosol experiment.
By the time the T0 mouldings arrive, we ought to have a reasonably clear idea of what the engine is going to do. The moulding process can introduce its own changes through polymer shrinkage, tolerances, surface finish and material behaviour. So we inspect the parts, measure the features that matter and check the assembled device. That includes the piercing action, the openings produced in the foil, and the overall airflow resistance of the fully assembled device.
Mechanical checks and a familiar resistance value do not, by themselves, establish that the aerosol is unchanged. NGI testing lets us compare the aerodynamic particle size distribution from the moulded device directly with the data from the representative SLA hardware. We want those first mouldings to confirm the aerosol behaviour we have already characterised. Where the results differ, we have an established reference against which to investigate what has changed in the moulded implementation.
The QCB comparison below used a 75 mg fill of CHI-F-057 (15% w/w) at 36.5 L/min (~4 kPa). Fine particle dose remained approximately 3.2 mg across the SLA reference, SLA Clinical device and two T0 moulded devices, with similar MMAD and slightly higher mean GSD in the moulded devices.
*From SLA to T0 mouldings: QCB fine particle dose, MMAD and GSD remain comparable.*
For carrier-based Quattrii, that investigation centres on the blister and the piercing system, because the blister forms the deagglomeration and classification chamber. The inlet openings, the cavity geometry and the surrounding airflow features govern the conditions experienced by the powder. A lid-foil opening that fails to reproduce the intended shape is therefore an aerodynamic issue, even if the device appears to have pierced the blister quite successfully.
> Mechanical checks and a familiar resistance value do not, by themselves, establish that the aerosol is unchanged.
Carrier-free Quattrii gives us a different set of features to watch. Its separate tuneable deagglomeration architecture has its principal tuning dimensions concentrated in one relatively simple moulded component. We can develop the formulation-specific geometry using SLA parts, then reproduce it in that component without turning the rest of the Clinical platform into a new development project. The primary package and the way the patient operates the device can remain the same.
A pharmaceutical partner may eventually want a reusable inhaler, a disposable product or a multi-unit-dose device, with an external form quite different from Quattrii Clinical. The intended patient group and use environment will shape its human-factors requirements, while manufacturing volumes and assembly strategy will influence how it is made. The Clinical platform lets that partner evaluate the formulation, primary package and aerosol engine together before those later product decisions are fixed. We want the commercial development team to start with an engine whose behaviour we understand, and a clear record of the geometry and operating conditions on which its performance depends.
**This blog post was originally published as part of a series of [LinkedIn articles](https://www.linkedin.com/pulse/912-tuning-inhaler-formulation-david-harris-xdwde/), written by [David Harris.](https://www.linkedin.com/in/davidstuartharris/)**
#### [David Harris](https://chi.uk/chi-blog/author/david-harris)
David is passionate about improving the lives and wellbeing of patients. He has focused his 30-year career on the development of medical products, mainly in the field of respiratory drug delivery. As a physicist he enjoys the complex and challenging science that underpins inhalation and has more than 50 patent applications in the field, many of which have become part of commercially successful products. David is responsible for the technical development of new products.
[mailto:david.harris@chi.uk](mailto:david.harris@chi.uk)
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"text" : "Quattrii Clinical looks like an inhaler developed by people who are unusually interested in what air does inside small holes, which is a reasonably accurate description of us. We have spent a great deal of time on the aerosolisation engine, the blister and the way the two interact, and considerably less on making the casing handsome. At this stage, we are quite comfortable with the resulting ugly duckling. These devices are intended for pharmaceutical evaluation and early clinical studies. They need to handle the right primary package, pierce it correctly and reproduce the airflow conditions on which aerosol performance depends. They also have to assemble reliably and be straightforward to use in the intended clinical setting. That is enough to keep us occupied before anyone starts asking whether the mouthpiece could have a more elegant curve… An attractive CAD rendering can acquire a surprising amount of authority early in a project. Once the external shape is established, the engineering team can find itself trying to fit the required airflow geometry into whatever space is left. In a DPI, a small change to an inlet or passage can affect how energy reaches the formulation, so we want enough freedom to understand those relationships before fixing the product around them. The two Quattrii Clinical formats shown in hand, illustrating their small size. Much of that work is done using high-resolution SLA parts, which let us alter dimensions and test the resulting aerosol without commissioning a new mould tool every time we learn something new. We are already designing for injection moulding, including draft angles, wall geometry and tooling considerations in the components we print. We want the development data to describe something we can eventually make. An attractive CAD rendering can acquire a surprising amount of authority early in a project. Surface finish and small airflow holes can make this work a little less convenient than simply pressing ‘print’. Where finish affects the airflow, we can bead blast or polish the SLA component to make it more representative of the moulded part. Some features are printed with additional sacrificial material which we subsequently remove, allowing us to finish them back to the nominal geometry. Small holes can also be machined or carefully reamed after printing, so that printer resolution has as little influence as practicable on the aerosol experiment. By the time the T0 mouldings arrive, we ought to have a reasonably clear idea of what the engine is going to do. The moulding process can introduce its own changes through polymer shrinkage, tolerances, surface finish and material behaviour. So we inspect the parts, measure the features that matter and check the assembled device. That includes the piercing action, the openings produced in the foil, and the overall airflow resistance of the fully assembled device. Mechanical checks and a familiar resistance value do not, by themselves, establish that the aerosol is unchanged. NGI testing lets us compare the aerodynamic particle size distribution from the moulded device directly with the data from the representative SLA hardware. We want those first mouldings to confirm the aerosol behaviour we have already characterised. Where the results differ, we have an established reference against which to investigate what has changed in the moulded implementation. The QCB comparison below used a 75 mg fill of CHI-F-057 (15% w/w) at 36.5 L/min (~4 kPa). Fine particle dose remained approximately 3.2 mg across the SLA reference, SLA Clinical device and two T0 moulded devices, with similar MMAD and slightly higher mean GSD in the moulded devices. From SLA to T0 mouldings: QCB fine particle dose, MMAD and GSD remain comparable. For carrier-based Quattrii, that investigation centres on the blister and the piercing system, because the blister forms the deagglomeration and classification chamber. The inlet openings, the cavity geometry and the surrounding airflow features govern the conditions experienced by the powder. A lid-foil opening that fails to reproduce the intended shape is therefore an aerodynamic issue, even if the device appears to have pierced the blister quite successfully. Mechanical checks and a familiar resistance value do not, by themselves, establish that the aerosol is unchanged. Carrier-free Quattrii gives us a different set of features to watch. Its separate tuneable deagglomeration architecture has its principal tuning dimensions concentrated in one relatively simple moulded component. We can develop the formulation-specific geometry using SLA parts, then reproduce it in that component without turning the rest of the Clinical platform into a new development project. The primary package and the way the patient operates the device can remain the same. A pharmaceutical partner may eventually want a reusable inhaler, a disposable product or a multi-unit-dose device, with an external form quite different from Quattrii Clinical. The intended patient group and use environment will shape its human-factors requirements, while manufacturing volumes and assembly strategy will influence how it is made. The Clinical platform lets that partner evaluate the formulation, primary package and aerosol engine together before those later product decisions are fixed. We want the commercial development team to start with an engine whose behaviour we understand, and a clear record of the geometry and operating conditions on which its performance depends. 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