For more than 260 million people worldwide with asthma, inhalers are essential. However, studies show incorrect use in 12–71% of cases, up to 86% for hospitalized patients, and as high as 97% among children, reducing the dose they actually receive. Many users struggle with using their inhalers correctly, whether because of technique mistakes, inconsistent use, or age. As a result, the medicine often doesn’t reach the lungs as it should. Now, researchers at Kiel University in Germany are using ultra-precise 3D printing to redesign the tiny carriers inside dry-powder inhalers, aiming to make drug delivery much more effective.

Why do inhalers sometimes fall short?

Professor Regina Scherließ. Image courtesy of Kiel University.

Inhalers deliver medicine straight to the lungs, which is the best place for treating asthma. That makes them the alternative of choice versus pills or injections. But in everyday use, inhalers often don’t work well because people make mistakes or don’t use them regularly.

In fact, studies estimate that anywhere from 50% to 94% of patients misuse their inhalers due to technique mistakes like not inhaling deeply or coordinating incorrectly. On top of that, many people don’t take their inhalers as prescribed, with global estimates ranging from 43% to as high as 80%.

This combination of misuse and skipping doses can lead to increased asthma symptoms, more flare-ups, and even hospital visits, making things harder for people and the hospital system.

A team of researchers led by Professor Regina Scherließ at Kiel University wondered if a better design could fix this problem. To tackle the issue, they used 3D printing to create millions of identical, “hair-thin carrier particles” with exact shapes. In their study, one design (dubbed “Pharmacone”, with star-like protrusions) performed incredibly better, delivering four times more of the medicine into the lungs compared to other shapes. According to the scientists, the sharp angles likely cause particles to bump and rotate more, releasing the drug more effectively.

The work was published in the Nature portfolio journal Communications Materials, in a paper titled “Aerodynamic performance of tailored microparticles as carriers in dry powder inhaler formulations made by multi-focus multi-photon 3D laser printing.” The paper details how different geometries affected drug release and says the star-shaped Pharmacone design was the most effective.

Designs of the potential carrier particles. Image courtesy of Kiel University

Is this just theoretical?

For now, yes. Basically, because these are model particles for lab experiments, and are not ready for actual inhalers right now. But there is definitely potential. Inhaler design has been slowly evolving, with devices like Easyhaler® showing more regular use and control, and lower error rates in some clinical studies. Still, most patients haven’t experienced the benefits of such precise design, at least not yet.

Even small improvements can make a big difference. One study in the UK estimated that poor inhaler technique in about 366,000 asthma/Chronic Obstructive Pulmonary Disease (COPD) patients led to £16.2 million in unplanned healthcare events each year. Similarly, Spain’s lost resources due to misuse reached into the millions of euros. Better inhalers could help cut these costs.

A design like Pharmacone could help more medicine reach the lungs, even if a patient’s technique isn’t perfect. With better mechanics, the inhaler itself could do more of the work, compensating for poor coordination or inconsistent inhalation flow, explain the researchers. But patients aren’t all the same, especially kids and older adults. For example, fewer than 20% of elderly COPD patients use inhalers correctly, with even lower rates for devices like classic “spray” inhalers and a type of dry powder inhaler (DPI) called Turbuhalers, where proper use has been recorded at just 11.9% and 10%, respectively.

Pharmacone under the scanning electron microscope:
 the image shows Pharmacone carrier particles after mixing with the model drug. Image courtesy of Kiel University.

While these particles are still experimental, for now, biodegradable versions need to be developed before they can move into clinical use. Another hurdle is scaling up production. For this, the team turned to two-photon polymerization (2PP) for its nanometer resolution. The method works by focusing a laser into a photosensitive material, hardening it point by point with incredible precision. Traditionally, 2PP has been too slow for large-scale work, but a breakthrough at the Karlsruhe Institute of Technology (KIT) recently changed that. By introducing parallelization, researchers at KIT made it possible to print 49 structures simultaneously, instead of one at a time. Using this upgraded system, the Kiel University team could successfully produce millions of identical, hair-thin particles in series. This is an incredible step forward in making experimental designs like the Pharmacone practical for drug development.

The metamaterial printed with the new system consists of a complex three-dimensional lattice structure on the micrometer scale. Image courtesy of Vincent Hahn, Karlsruhe Institute of Technology.

Inhalers are only as effective as the way they’re used, and misuse is still one major problem.. Kiel University’s 3D printed Pharmacone particles are a great way to prove how smarter design could help more medicine reach the lungs, and a wonderful promise of better inhalers.