Mastering Microfluidic Chips: An In-Depth Definition
Microfluidic chips, also known as a lab-on-a-chip or biochips, are small-scale devices used across diverse scientific studies and industrial fields. They allow precise control, manipulation, and analysis of tiny volumes of fluids.
Key takeaways
- A microfluidic chip is a device of micro-channels, typically 5 to 500 µm across, in which small volumes of liquid are moved, mixed and analyzed.
- At these dimensions viscous forces dominate inertia, so liquid in a microfluidic chip moves in laminar streams, a regime described by a low Reynolds number [1].
- A microfluidic chip has no pump of its own: an external pressure controller, syringe pump or peristaltic pump drives the liquid, and the resulting flow depends on the system’s resistance and the fluid’s viscosity [2].
- Silicon and glass were the first chip materials; elastomers such as PDMS brought inexpensive rapid prototyping, and polymer devices have become more widespread than glass thanks to lower production expenses [3,4].
- Key milestones include a gas chromatograph on a silicon wafer in 1979 [5], the μTAS concept in 1990 [6], PCR amplification on a chip in 1998 [7] and Drop-seq in 2015 [8].
Microfluidic chip definition
A microfluidic chip is a network of micro-channels, connected to the outside world through inlet and outlet ports, in which liquids are injected, mixed, reacted and analyzed. The channel geometry is designed for one application, and an external instrument sets the pressure or flow rate that moves the liquid through the microfluidic chip.
Microfluidic chips, often referred to as lab-on-a-chip devices, are miniature platforms that manipulate and analyze small volumes of fluids. These chips, which feature molded or patterned micro-channels, integrate various functions, such as mixing, pumping, and sensing, onto a compact substrate, enabling precise control over minute amounts of liquids.
Inlet and outlet ports connect this network to the external environment. Liquids or gases can be injected, managed, and removed from the microfluidic chip through passive or active methods, which may involve pressure/flow controllers, syringe pumps, or peristaltic pumps. The microscale fluidic chip’s channels may have varying inner diameters, typically ranging from 5 to 500 µm, but today’s fabrication techniques enable structures with sub-micrometer precision.
The channel network must be specifically designed for the desired application and analysis (cell culture, organ-on-a-chip, DNA analysis, lab-on-a-chip, microfluidic droplets, etc.).
A brief history of microfluidic chips
Microfluidic chips grew out of microelectronics. Silicon micromachining produced the first chip-based analyzer in 1979 [5], the miniaturized total chemical analysis system was formalized in 1990 [6], and polymer chips later brought the technology into biology research laboratories [9].
The roots of microfluidics trace back to the mid-20th century. However, it was in the late 20th and early 21st centuries that the field truly blossomed.
Miniaturization techniques have been continuously shaping the microelectronics technology and its ability to produce devices for a broad range of applications. Downscaling the dimensions of transistors has been pursued in the industry to fulfill the growing demand for smaller, faster and more energy-efficient systems [10]. In the late 1960s, a new field emerged known as microelectromechanical systems (MEMS).
This field laid the foundations for the miniaturization of mechanical systems, with the development of micromachining technology based on silicon semiconductor technology. It was during this era that engineers began realizing the capabilities of silicon chips in processing elements such as chemicals, motion, and light.
1950s-1970s: Early Developments
Pioneering work by inventors and engineers such as Rune Elmqvist, whose inkjet recorder was patented in 1951 [11], and Stephen Terry, who built a gas chromatograph on a silicon wafer at Stanford University [5], laid the groundwork for microfluidic concepts.
1980s-1990s: Emergence of Lab-on-a-Chip
The term “lab-on-a-chip” gained prominence as researchers explored ways to miniaturize and integrate laboratory processes.
2000s-Present: Rapid Advancements
Microfluidic chips found applications in various fields, including biology, chemistry, and medicine, driving a surge in research and development.
Key Milestones:
First Lab-on-Chip (1979):
In 1979, the first glimpse of the future emerged as Terry, Jerman and Angell reported a gas chromatographic air analyzer fabricated on a silicon wafer [5], an early forerunner of the lab-on-a-chip that laid the foundation for a revolutionary era in microfluidics.
Polymerase Chain Reaction (PCR) on a Chip (1998):
The demonstration of continuous-flow PCR on a microfluidic chip by Kopp, de Mello and Manz [7] showcased the potential for DNA amplification in a miniaturized format.
Organ-on-a-Chip (2010s):
Advancements in mimicking physiological conditions on microfluidic platforms led to the development of “organ-on-a-chip” devices, revolutionizing drug testing and disease modeling.
Point-of-Care Diagnostics (2010s):
Microfluidic chips played a pivotal role in the development of portable, rapid diagnostic devices, transforming healthcare by enabling on-site testing.
Drop-Sequencing protocol developed by Macosko et al. (2015)
Drop-Seq marked a significant milestone as it introduced a high-throughput method for single-cell RNA sequencing, propelling advancements in understanding cellular diversity and gene expression [8].
How a microfluidic chip works
A microfluidic chip works by guiding liquid through channels so narrow that viscous forces dominate inertia. The regime is therefore laminar: neighboring streams slide past one another without turbulent mixing, and the flow rate is set by the pressure applied across the chip, the resistance of the channel network and the viscosity of the liquid [1,2].
Why liquids move in laminar streams in a microfluidic chip
This regime is captured by the Reynolds number, which compares inertial and viscous forces [1]:
Re = ρUL / μ
where ρ is the fluid density (kg/m³), U the mean velocity of the liquid (m/s), L the characteristic channel dimension (m) and μ the dynamic viscosity (Pa·s). Because L is micrometric, Re stays low in most microfluidic chips and inertial effects become negligible [1]. Two liquids injected side by side therefore travel as separate streams and mix by diffusion only, the principle behind sensing and filtering devices built on parallel laminar streams [1].
Each channel also opposes the liquid’s motion with a hydraulic resistance that depends on its length, its cross-section and the viscosity of the liquid. Our review of flow resistance shows how to estimate it from the dimensions of a microfluidic chip and its tubing.
How liquid is driven through a microfluidic chip
A microfluidic chip has no pump of its own. Displacement systems such as syringe and peristaltic pumps push liquid mechanically. Pressure-based instruments instead pressurize the reservoir that feeds the chip, so the delivered flow rate follows from the applied pressure and the resistance of the system. Our flow control comparison sets out how the three approaches differ, and our guide to tubing selection covers the connection layer between instrument and chip.
In a Fluigent setup, the Flow EZ pressure-based flow controller drives the liquid and the FLOW UNIT inline flow sensor measures it. When the two are combined, the Flow EZ adjusts the pressure applied to the microfluidic chip automatically to hold a set flow rate [2].
Material and production methods
Microfluidic chips are made mainly from silicon, glass, elastomers such as PDMS, thermoplastics such as PMMA, hydrogels and paper. The material sets the chip’s optical, chemical and mechanical properties, its price and the production methods available, so it is usually chosen as a compromise between ease of prototyping and device performance [3,4].
Explore the world of microfluidic chip fabrication and production methods. These chips, crucial in lab-on-a-chip technology, are crafted from materials like silicon, glass, or polymers such as PDMS (Polydimethylsiloxane). The production methods vary, tailored to the chosen material.
Example of glass microfluidic chip (manufactured by Little Things Factory GmbH)
The evolution of microfluidics traces back to the late 20th century with the development of inkjet printer heads. This breakthrough showcased the generation of micron-sized droplets using piezoelectric or thermal effects.
In 1990, Manz et al. introduced the concept of miniaturized total chemical analysis systems (μTAS) [6], aiming to integrate diverse laboratory processes into a compact chip-sized platform.
This revolutionary idea sought to simplify and enhance complex chemical analyses by minimizing the size and complexity of traditional laboratory setups.
Subsequently, companies emerged, utilizing these systems for life science applications. The adoption of rapid prototyping and polymer replication, particularly PDMS, as an alternative to silicon processing, accelerated academic research. This era ushered in new terminologies such as “microfluidics” and “lab-on-a-chip” (LOC), reshaping the landscape of scientific exploration.
Microfluidic chip materials compared
| Material | Key properties | Typical uses |
|---|---|---|
| Silicon | First-generation material inherited from microelectronics; expensive to microfabricate [3] | Early analytical chips; integration with microelectronics |
| Glass | Optically transparent, chemically inert and biocompatible; surface functionalization through silanol chemistry adds processing steps [4] | Capillary electrophoresis and applications involving solvents [3] |
| Elastomers (PDMS) | Low-cost rapid prototyping; allows dense integration of valves on chip [3] | Research prototypes, parallel liquid handling, cells grown inside channels [3] |
| Thermoplastics (PMMA and others) | Rigid below the glass-transition temperature, so they withstand high pressure; molded at relatively high temperatures [4] | Rigid polymer devices, including hybrid chips [4] |
| Hydrogels | Highly permeable: molecules diffuse without bulk liquid movement [3] | 3D cell models, diffusion gradients, actuators [3] |
| Paper | Extremely cheap to prepare and easy to use [3] | Point-of-care assays [3] |
For each substrate and production route in depth, see our review of microfluidic chip fabrication, materials and methods.
Who makes microfluidic chips?
Microfluidic chips are supplied by specialized manufacturers and research foundries, and many laboratories prototype their own devices, choosing materials as a compromise between ease of prototyping and device performance [3]. Fluigent supplies a range of chips, several of them developed with partner manufacturers, designed to connect directly to its pressure-based instruments.
| Partner manufacturer | Example chips | Example application |
|---|---|---|
| Beonchip | Be-Flow, Be-Doubleflow, Be-Transflow | Organ-on-a-chip and air-liquid interface models |
| FlowJEM | Drop-seq chip | Single-cell RNA sequencing in droplets |
| Secoya Technologies | RayDrop single and double emulsion devices | Encapsulation and multiple emulsions |
| microfluidic ChipShop | Herringbone mixer (Fluidic 187), spiral sorter (Fluidic 382) | Passive mixing; size-based particle sorting [12] |
| Micronit | Glass porous media chips | Enhanced oil recovery research [13] |
Our chip range
The range covers two families. For organ-on-a-chip work, chips such as Be-Flow, Be-Doubleflow and Be-Transflow, developed by Beonchip, support perfusion studies, dual-channel models and air-liquid interface co-cultures. For emulsion work, chips such as EZ Drop, the Drop-seq chip and the RayDrop single and double emulsion devices generate monodisperse emulsions. The complete microfluidic chip range lists every chip with its specifications.
Beonchip S. L. was founded in 2016 at the University of Zaragoza by Ignacio Ochoa (specialist and PhD in biology), Luis Fernández (PhD in microtechnology) and Rosa Monge (PhD in mechanical Engineering).
Therefore, Beonchip have multidisciplinarity in its roots, and their team is proof of that. The collaboration of engineers and biologists has been key to design the most user friendly and accessible organ on chip devices that are true to the physiological environment of the body.
FlowJEM technology was developed for research and development projects by microfluidic researchers and engineers like you.
Microfluidic devices fabricated by FlowJEM have a broad range of applications, including but not limited to chemistry, materials science and technology, nanoscience, pharmaceutical science, biology, bioengineering and medicine.
FlowJEM’s goal is to meet the demands for high quality, fast turnaround time and low cost. Work with us to develop your ideas into prototypes or transition your prototypes to volume production.
Secoya Technologies develops innovative production technologies and equipment by a smart use of intensified operational units. It results in stable and reliable processes – at any scale – producing high quality (bio-)pharmaceutical products
Using cutting-edge technologies as sub-micrometric 3D printing, Secoya Technologies has developed the RayDrop, a microfluidic device that is able to continuously produce micro-sized droplets at a very high frequency (kHz) and with a very narrow size distribution (high monodispersity). Its use for the encapsulation of active ingredients and multiple emulsions has been demonstrated.
microfluidic ChipShop offers a wide off-the-shelf selection of microscale fluidic chips from thermoplastic polymers and complementary accessories. They furthermore support customized prototyping as well as volume production services from one to millions of chips, from simple microfluidic devices to complex lab-on-a-chip-systems.
Example: a mixing chip. Because liquids in a microfluidic chip move in laminar streams, two solutions injected side by side mix only slowly, by diffusion. Mixing chips add geometry to the channel to speed this up. In the staggered herringbone mixer, angled ridges on the channel floor fold the streams over one another. As a result, the channel length needed for mixing grows only logarithmically with the Péclet number, which compares transport by the moving liquid with transport by diffusion [14]. microfluidic ChipShop’s catalogue includes herringbone mixer chips built on this principle, such as the Fluidic 187.
Example: cell sorting. In a Fluigent application note produced with microfluidic ChipShop, a spiral chip, the Fluidic 382, separated a mixture of 7.3 µm and 15.25 µm fluorescent polystyrene beads by size alone, as a model for passive cell sorting [12]. In the curved channel, Dean forces and lift forces drive particles of different sizes to different equilibrium positions. The larger beads settle closer to the inner wall, so each size leaves through its own outlet. A Flow EZ drove the sample and a FLOW UNIT monitored it, and two sorting units on the chip separated the beads at 1.5 mL/min and 150 µL/min [12]. The chip and instruments are available together as the Microfluidic Size Cell Sorting Pack.
Micronit is the leading innovator and global partner in design, development and manufacturing of customer specific lab-on-a- chip solutions for life science and health applications.
With over 20 years of experience, a highly qualified team, state-of-the-art technologies, and certified manufacturing facilities, we deliver innovative and competitive products to our customers for life science research towards personal health applications.
Example: porous media chips for enhanced oil recovery. Micronit fabricates transparent glass chips with engineered pore networks that reproduce the structure of rock, so oil and water displacement can be observed pore by pore. In a Fluigent case study, researchers at the Université de Bordeaux and Texas Tech University combined Micronit chips with Flow EZ pressure controllers and FLOW UNIT sensors to study two-phase transport [13]. The Bordeaux work used the experimental data to validate numerical models of multiphase transport. The Texas Tech study, in an oil-wet network, found that recovery efficiency decreased as the invaded volume increased, owing to stronger capillary trapping [13]. The full case study on microfluidic porous media models for enhanced oil recovery details both setups.
Frequently Asked Questions
What are microfluidic chips used for?
Microfluidic chips are used to grow cells under perfusion, build organ-on-a-chip models, generate emulsions, sort particles and cells, amplify and analyze DNA, and run portable diagnostic tests. Each use relies on a microfluidic channel network designed for it: PCR on a chip [7] and single-cell RNA sequencing in nanoliter droplets [8] are two established examples. Our overview of chip applications covers each field in depth.
What are microfluidic chips made of?
Microfluidic chips are made from silicon, glass, elastomers such as PDMS, thermoplastics such as PMMA, hydrogels or paper. Glass and silicon came first but are expensive to microfabricate; PDMS allows inexpensive rapid prototyping, and polymer devices have become more widespread than glass thanks to lower production expenses [3,4].
How much does a microfluidic chip cost?
The cost of a microfluidic chip depends on three factors: the substrate material, the smallest feature size the design requires and the number of chips produced. Glass and silicon are relatively expensive to microfabricate, elastomers such as PDMS allow low-cost rapid prototyping, and paper-based devices are among the cheapest to prepare [3]. For the price of a specific Fluigent chip, contact our team .
What is the difference between a microfluidic chip and a lab-on-a-chip?
A microfluidic chip is the fluidic substrate: a network of micro-channels that contains and moves liquids. A lab-on-a-chip uses that substrate to integrate the complete steps of an analysis in a single device, from sampling and transport to reactions, separation and detection. This idea was formalized in 1990 as the miniaturized total chemical analysis system, or μTAS [6]. Every lab-on-a-chip is microfluidic, but not every microfluidic chip is a lab-on-a-chip.
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