Organ-on-a-chip: microfluidic devices that mimic human organ function

An organ-on-a-chip is a microfluidic device containing living human cells in continuously perfused chambers, arranged to reproduce tissue- and organ-level functions such as a breathing lung interface. Organs-on-chips, also called microphysiological systems, are used to model disease, test drugs and reduce reliance on animal studies.

Key takeaways

• Bhatia and Ingber defined organs-on-chips in Nature Biotechnology (2014) as perfused microfluidic devices that simulate tissue- and organ-level physiology.
• The lung-on-a-chip from Huh et al. (Science, 2010) showed that adding breathing-like stretch changed how lung tissue responded to nanoparticles.
• Chips trade biological self-organization for engineering control: flow, forces, layout and real-time measurement.
• US law now lets drug applications rely on nonclinical tests that include microphysiological systems, making chips part of the new approach methodologies landscape.
• Combining chips with brain organoids could improve perfusion, stability and measurement for neuroscience and biocomputing.

What is an organ-on-a-chip? #

An organ-on-a-chip is a small engineered device, often molded in a transparent silicone polymer, with channels a fraction of a millimeter wide. Living cells line these channels and are fed by flowing medium. Bhatia and Ingber’s 2014 review described the defining features: microchip manufacturing methods, continuously perfused chambers, and cells arranged to recreate multicellular architectures, tissue-tissue interfaces, physical and chemical microenvironments and vascular perfusion. They argued that this produces levels of function not possible in conventional 2D or 3D culture, while allowing high-resolution, real-time imaging.

The technology grew out of microfluidics, the engineering of fluid flow at micrometer scales, which Whitesides surveyed in Nature (2006). At those scales flow is smooth and predictable, so researchers can deliver nutrients, drugs and signals with precision.

Core components #

A typical organ chip includes:

• Microchannels that carry medium, blood substitutes or air.
• A porous membrane separating two cell types, such as epithelium and endothelium, to form a tissue barrier.
• Mechanical actuation in some designs, for example vacuum chambers that stretch the membrane.
• Sensors or access ports for sampling, imaging and electrical measurement.
• Human cells, from primary tissue, cell lines or induced pluripotent stem cells.

How is an organ chip experiment run? #

A typical workflow looks like this:

1. Design the device, choosing channel geometry, membrane and any mechanical actuation to match the tissue being modeled.
2. Fabricate and sterilize it, often by molding a polymer against a master and bonding it to glass or plastic.
3. Coat surfaces with extracellular matrix proteins so cells can attach.
4. Seed the cells, often two or more types on opposite sides of a membrane.
5. Start perfusion at flow rates that feed cells without damaging them through shear stress.
6. Apply conditions, such as stretch, a drug or an infectious agent.
7. Measure outcomes, including imaging, barrier integrity, secreted molecules and, for excitable tissue, electrical activity.

Each of these choices is an experimental variable. Two labs using the same cells in differently designed chips can see different results, which is one reason standardization matters.

How did the lung-on-a-chip work? #

The landmark example is the lung-on-a-chip reported by Huh et al. in Science in 2010. The device placed human lung air-sac (alveolar) cells on one side of a thin porous membrane and blood-vessel cells on the other, recreating the alveolar-capillary interface. Side chambers applied cyclic vacuum to stretch the membrane, mimicking breathing.

The authors reported that the chip reproduced integrated responses to bacteria and inflammatory signals. In nanotoxicology tests, mechanical strain made the tissue’s toxic and inflammatory responses to silica nanoparticles stronger and increased nanoparticle uptake into the vascular channel, with similar effects observed in whole mouse lung. The broader point was that a cell’s physical environment, not only its chemistry, changes the biology you measure.

How is an organ-on-a-chip different from an organoid? #

The two are often confused because both aim to make lab-grown human tissue more realistic. They take opposite routes.

Ingber’s 2022 review in Nature Reviews Genetics discusses how the approaches are converging: organoids can be placed inside chips to gain flow and vascular-like interfaces, while chips gain the richer cell composition of organoids. For a deeper look at standard organoid culture, see how brain organoids are grown.

What are organs-on-chips used for? #

1. Disease modeling, recreating features of infection, inflammation or genetic disease in human tissue.
2. Drug efficacy and toxicity testing, including organ-specific toxicity that animal models may miss.
3. Personalized medicine, using cells from an individual patient.
4. Multi-organ systems, linking chips to study how a compound is processed by one tissue and affects another.
5. Regulatory science, as candidate methods for safety assessment.

Leung et al.'s 2022 guide in Nature Reviews Methods Primers covers practical design, fabrication and validation, and highlights standardization as a continuing challenge.

How do organs-on-chips relate to animal testing rules? #

In the United States, the FDA Modernization Act 2.0 amended the Federal Food, Drug, and Cosmetic Act so that drug applications refer to “nonclinical tests” rather than preclinical tests including animal tests. The bill text defines nonclinical tests to include animal tests as well as non-animal or human biology-based methods, naming cell-based assays, microphysiological systems, and bioprinted or computer models. The law permits these alternatives; it does not ban animal testing. This places organ chips among the broader family of new approach methodologies that regulators are now evaluating.

Can you build a brain-on-a-chip? #

Researchers have built chips that model pieces of nervous system function, such as the blood-brain barrier or neurons cultured under controlled flow, and have housed brain organoids in perfused microfluidic chambers. Brain chips are less established than lung, liver or gut chips, in part because neural function depends on long-range connectivity that is hard to recreate at small scale.

For biocomputing, chip engineering addresses practical problems:

• Life support. Organoids lack blood vessels, so perfusion can improve nutrient delivery, complementing efforts toward organoid vascularization.
• Electrode integration. Chips can be built on top of a microelectrode array to record electrophysiology while controlling flow.
• Chemical inputs. Timed delivery of compounds offers a second channel alongside electrical closed-loop stimulation.
• Connecting regions. Channels can guide connections between separately grown tissues, an engineered relative of the assembloid.

These integrations are discussed further in bio-silicon hybrid computing and the future of biocomputing.

What are the limitations? #

• Partial biology. A chip models part of an organ, not a whole organism with immune, hormonal and metabolic interactions.
• Material effects. Common polymers can absorb small hydrophobic molecules, distorting drug concentrations.
• Standardization and validation. Many devices are custom, which makes cross-lab comparison and regulatory acceptance slower.
• Throughput and cost. Complex chips can be harder to scale than plate-based assays.
• Cell source. Results depend on which cells are used and how mature they are.

As chips and organoids converge, the parameters of each run (flow rates, medium, cell source, timing) become part of the result. Logging them alongside every recording is part of what we are building into the Organoid Programming platform, so that organ-on-a-chip style life support and electrophysiology can be reproduced, not just reported.

Frequently asked questions

What is an organ-on-a-chip in simple terms?

An organ-on-a-chip is a small, usually transparent device, often a few centimeters across, with tiny channels lined with living human cells. Fluid flows through the channels as blood or air would in the body, and some devices also stretch or squeeze the cells. The aim is to make cells behave more like they do inside a real organ than they would in a flat dish.

What was the first famous organ-on-a-chip?

One of the best-known early examples is the lung-on-a-chip reported by Huh and colleagues in Science (2010). It recreated the interface between lung air sacs and blood capillaries on a flexible membrane that could be stretched to mimic breathing. The authors reported that this mechanical strain increased toxic and inflammatory responses to silica nanoparticles.

What is the difference between an organoid and an organ-on-a-chip?

An organoid is a 3D tissue that self-organizes from stem cells, following developmental programs with relatively little external structure. An organ-on-a-chip is an engineered device in which researchers place cells in a designed layout with controlled flow and forces. Organoids offer biological complexity; chips offer control and measurement. The two are increasingly combined as organoids-on-chips.

Can organs-on-chips replace animal testing?

They can replace some animal tests and complement others, but not all of them yet. A single chip models part of one organ, not a whole body with metabolism, immunity and interacting organs. US law changed in 2022 so that drug applications can rely on nonclinical tests including microphysiological systems, rather than requiring animal tests, and regulators are working out where chips are sufficient.

Is there a brain-on-a-chip?

Yes, researchers have built chips that model aspects of brain tissue, such as the blood-brain barrier, neurons cultured with controlled flow, or brain organoids housed in perfused microfluidic chambers. These systems are less mature than lung, liver or gut chips. They are relevant to biocomputing because stable perfusion could keep neural tissue healthy for longer recordings.

What is a microphysiological system?

Microphysiological system, or MPS, is a broader term for in vitro platforms that recreate aspects of human tissue physiology at small scale, including organs-on-chips and some organoid-based systems. US regulators and legislators often use this term. The FDA Modernization Act 2.0 lists microphysiological systems among the nonclinical test methods that can support drug applications.

Sources

1. Huh, D. et al. (2010). Reconstituting organ-level lung functions on a chip. Science.
2. Bhatia, S. N. & Ingber, D. E. (2014). Microfluidic organs-on-chips. Nature Biotechnology.
3. Ingber, D. E. (2022). Human organs-on-chips for disease modelling, drug development and personalized medicine. Nature Reviews Genetics.
4. Leung, C. M. et al. (2022). A guide to the organ-on-a-chip. Nature Reviews Methods Primers.
5. S. 5002, FDA Modernization Act 2.0 (117th Congress), engrossed text. GovInfo.
6. Whitesides (2006). The origins and the future of microfluidics. Nature.