The appeal of lung-on-a-chip systems is straightforward. Conventional two-dimensional cell cultures strip away the organised tissue interfaces, fluid dynamics and mechanical forces that define the respiratory microenvironment, while animal models suffer from interspecies differences that often fail to predict human responses. By combining microfabrication and microfluidic control with pulmonary cell culture, chip platforms can reproduce epithelial-endothelial interfaces, air-liquid interface culture, vascular perfusion and even breathing-related strain, features first brought together in the landmark 2010 human lung-on-a-chip by Huh and colleagues at Harvard. Since then, the design space has exploded, encompassing immune-competent models, patient-derived cells, high-containment infection systems and inhalation exposure devices.

Yet the review’s central message is provocative: more complexity does not automatically mean better science. Membrane thickness, pore size, porosity, stiffness and extracellular matrix functionalisation are not passive structural details; they actively shape transport, cell attachment, mechanical deformation and signalling between compartments. Small-pore polyester membranes, for example, favour a compartmentalised epithelial barrier, while larger pores are needed if researchers want immune cells to migrate across the interface. Barrier fidelity and leukocyte recruitment therefore demand different, sometimes conflicting, interface properties, and choosing between them depends entirely on the question being asked.

Fluidic strategy introduces a similar set of trade-offs. Perfusion delivers nutrients, removes waste, transports drug compounds and mechanically stimulates endothelial cells, but volumetric flow rate alone does not define the cellular environment, because wall shear stress also depends on channel geometry and fluid viscosity. Pump-driven systems offer precise control over flow profiles but increase dead volume, bubble risk and operational burden. Pump-free, gravity-driven rocking platforms simplify operation and reduce contamination risk in high-containment viral infection studies, at the cost of less precise control over instantaneous flow. The authors argue that studies should routinely report the flow-generation method, channel dimensions and calculated or measured shear stress so that perfusion-mediated transport can be distinguished from endothelial mechanostimulation.

Mechanical actuation, the defining capability of breathing chips, receives particularly careful treatment. The review emphasises that breathing motion is not a single condition but a family of variables spanning strain magnitude, frequency, waveform and actuation mechanism. Recent studies show these parameters matter enormously: cyclic stretch combined with airflow can accelerate mucociliary maturation of airway epithelium, and dynamic strain can modify how cells respond to inhaled toxicants. In one striking example, an orthotopic lung cancer chip demonstrated that breathing-related deformation altered tumour proliferation, invasion, dormancy and even responsiveness to tyrosine kinase inhibitors, implicating mechanical cues in epidermal growth factor receptor and MET signalling. Therapeutic response, in other words, cannot always be attributed to cellular genotype and drug exposure alone when the mechanical microenvironment itself modifies phenotype.

The same principle applies to exposure delivery and cellular composition. A next-generation breathing chip integrated with whole-cigarette-smoke exposure reported an approximately sixty percent reduction in barrier resistance and a 4.5-fold increase in interleukin-8 expression, with dynamic strain accelerating barrier disruption relative to static conditions, results that submerged chemical extracts could never reproduce. Cellular complexity, meanwhile, should be justified functionally rather than maximised blindly. An immune-competent lung-on-a-chip modelling severe influenza found that adding tissue-resident macrophages generated cytokine profiles more closely matching patient bronchoalveolar lavage data, but reproducing the broader inflammatory storm of severe infection required resident and circulating immune populations, perfusable microvasculature and a five-micrometre-pore interface that permitted immune migration. Complexity earned its place by enabling a predefined function.

Manufacturing and quality control emerge as underappreciated determinants of credibility. Small variations in channel dimensions, membrane position, bonding or actuator geometry can alter shear stress, strain transfer and barrier behaviour, and such technical variation can easily masquerade as biological variability. The review calls for predefined tolerances on critical device attributes, functional quality-control criteria including leak testing and sensor calibration, batch traceability, and documented fabrication parameters. It also cautions that switching fabrication methods, from soft lithography in polydimethylsiloxane to thermoplastic replication for scalable production, can change gas permeability, surface chemistry and compound adsorption, and should therefore trigger re-verification of critical engineering and biological endpoints rather than being treated as a neutral process change.

To organise the path from bench to regulatory relevance, the authors propose a five-stage framework anchored to a clearly defined context of use. The first stage, engineering verification, confirms that the device reproducibly generates its intended physical environment, from verified strain fields to delivered smoke exposure. The second, biological qualification, demonstrates that this environment supports the specific biological functions the application requires, such as barrier integrity, mucociliary activity or immune-cell migration. The third stage, disease or pharmacological validation, requires reproducible detection of the target response against appropriate comparators, as illustrated by a human alveolus chip that reproduced radiation-induced DNA damage, inflammation and barrier disruption and then evaluated prednisolone and lovastatin as candidate countermeasures.

The final two stages demand the most stringency. Human concordance requires direct comparison of chip outputs with patient-derived or clinical reference data, a standard met in part by the influenza chip’s cytokine benchmarking against patient samples, but the authors warn that such evidence should not be stretched into broader claims of clinical prediction. Predictive performance, needed when a context of use involves therapeutic or toxicological decision-making, requires predefined metrics such as sensitivity, specificity or response discrimination against characterised reference datasets. Deployment and regulatory readiness then asks whether qualified performance survives manufacturing scale-up, automation and transfer between independent laboratories. The framework deliberately distinguishes physiological resemblance from demonstrated concordance, and concordance from clinically anchored prediction, so that each claim carries only the weight its evidence supports.

The review’s conclusion is a call for discipline over dazzle. Prioritising validated, fit-for-purpose performance over maximal complexity, the authors contend, offers a more credible route toward reliable respiratory research tools, drug development platforms and eventual regulatory decision support. Standardisation, they argue, should target terminology, reporting of critical parameters, reference controls and inter-laboratory reproducibility rather than forcing identical device architectures, since legitimate applications genuinely require different designs. As regulators, including the United States Food and Drug Administration in recent draft guidance, increasingly frame new approach methodologies around context of use, the framework provides developers with a practical checklist: define the question and acceptance criteria before experimentation, report engineering parameters with tolerances, benchmark against prespecified comparators, incorporate human datasets when predictive claims are intended, and prove that performance holds across batches, operators and laboratories. If the field follows that path, the miniature lungs growing on chips today may earn the trust needed to influence tomorrow’s drug decisions.

Subject of Research: Engineering and translational validation of lung-on-a-chip microphysiological devices for respiratory disease modelling and drug testing

Article Title: Engineering Lung-on-a-chip microdevices for respiratory disease modelling and drug testing: A fit-for-purpose framework for design and translational validation

Article References: Cheong, S. Y., Liew, T. I. Z., Wong, C. K., Teng, X. X., Cha, X. Y., Ng, N. C.-S., Wong, R. S.-Y., & Goh, B. H. (2026). Engineering Lung-on-a-chip microdevices for respiratory disease modelling and drug testing: A fit-for-purpose framework for design and translational validation. Biomedical Microdevices, 28(3), Article 62. https://doi.org/10.1007/s10544-026-00849-3

Image Credits: AI Generated

DOI: 10.1007/s10544-026-00849-3

Keywords: lung-on-a-chip, microfluidics, organ-on-chip, respiratory disease modelling, drug testing, microphysiological systems, translational validation, mechanical strain, inhalation toxicology, quality control, regulatory science, context of use