Microfluidics is the science of controlling and manipulating fluids, allowing the analysis and use of lower levels of sample, chemical and reagent volume. The technology provides quick reaction times, optimized sensitivity, greater temperature control, portability and simpler automation at a cost-effective price. The technology has significant potential to be utilized in numerous applications, and OEM microfluidics companies like Dolomite Microfluidics and Fluigent are focused on working with their customers to support the technology’s growth into other sectors.

Both Dolomite and Fluigent provide OEM solutions for microfluidics, and are involved in collaborations and initiatives to help drive microfluidic technology across multiple applications. Dolomite partnered with OptoRobotix and Bioneer in 2013 to develop a cutting-edge stem cell handling technology, and, more recently, joined forces with Partek in May to develop a single-cell analysis pipeline on Partek’s NGS data analysis software, Partek Flow.

A spinout from the Curie Institute, Fluigent was established in Paris in 2005. In April, Fluigent partnered with Sculpteo, a 3D printing service company, and 10 other companies as the lead of the HoliFAB project, a Horizon 2020 initiative dedicated to accelerating industrialization in microfluidics using 3D printing.

IBO spoke with Richard Gray, head of Dolomite, and Robert Pelletier, president of Fluigent, to discuss the utilization, challenges and future of microfluidics.

Issues and Solutions

While microfluidic technology has great advantages, including ease of use, high throughput and multiplexed assays, quick and precise analyses, low reagent usage, and overall cost reductions, the technology is not without its limitations.

Fluid shear stress can be an issue in microfluidics, and it increases the more viscous a sample is and also due to fluid velocity. “Cell suspensions can be a challenge, particularly where the cells are fragile,” said Mr. Gray. “Care is also required where the fluids contain beads or particles which have a very different density to the fluid (for example, RNA capture beads sometimes have a 40% higher density than the fluid, and can drop out of suspension very quickly).” Other challenging sample types, as Mr. Pelletier, explained, are oils, blood, alginates and polymers. As Fluigent specializes in pressure-based solutions to improve flow control, the company uses pressure to solve the issues that challenging samples may come with. “Issues with viscous substances are typically resolved through either using higher pressures to drive flow rates, or through iterative chip designs to enlarge the channel sizes and improve flow characteristics,” said Mr. Pelletier.

Dolomite also has its own solution to address shear stress. “We’ve developed methods to feed these suspensions gently and successfully,” explained Mr. Gray. “Our Edge connection technology maintains flow in a single plane as it enters and exits the chip, thus reducing shear when compared to conventional connector methods (which require a 90 degree change of direction, often coupled with rapid deceleration and acceleration as fluid passes through inlet and outlet holes).”

Chips are an important tool in microfluidics devices, as they help control and confine fluids at a microscale level. The microfluidic chip provides many functionalities and allows for users to generate multi-step reactions without requiring a high level of expertise. Various materials are used to make microfluidics chips, such as Polydimethylsiloxane (PDMS), silicon, glass, hydrogel and paper, which each have their benefits. PDMS is most commonly used to create microfluidics chips due to its elasticity, permeability, transparency and low costs. However, a major drawback is that the material can absorb hydrophobic molecules and water vapor, which can then be released over the course of an experiment, potentially skewing results.

To address these challenges, Dolomite chiefly makes its chips from glass, which has proven to work best with the company’s customers’ applications. Mr. Gray explained that the benefits of glass include pressure capability, thermal performance, chemical resistance, precision, lifetime and ease of connection. Morover, Dolomite can customize the chip based on its customer’s application to ensure optimal performance. “We can coat glass chips to ensure they are hydrophobic when required,” said Mr. Gray. “We use a different coating when working with the fluorocarbon oils that are popular for cell biology work. Fluorocarbon oils absorb large amounts of gas, which can mean cells remain viable in droplets for many days.” If UV transparency is required, Dolomite uses fused silica (quartz), and can create plastic chips if glass is not viable, with polymers such as COC (Cyclic Olefin Copolymer) and COP (Cyclo Olefin Polymer), and acrylic glass, also known as PMMA, or Poly(methyl methacrylate). For example, Dolomite’s Nadia product family, an automated, microfluidic droplet-based system for single-cell research, uses a disposable injection molded 8-lane polymer chip.

“The main element is optimizing the entire system (chip and fluid handling) to achieve the desired performance.”

Dolomite continues to develop new and specialized methods to address chip challenges, as chips are a key component of the technology. “We have specialized channel designs; for example, our 3D pore technology was developed to handle challenges such as feeding sticky polymers,” Mr. Gray said. “We have also expanded our chemistry capability, and will shortly be launching new reagents and surfactants to improve performance and throughput for a range of applications.”

Keeping abreast with customers’ research and operational challenges is imperative for companies such as Dolomite and Fluigent. As Mr. Pelletier noted, although Fluigent is not a chip company by definition, it is important for the company to stay informed of various chip materials and applications in order to best serve its customer base. “The key is understanding one’s analytical needs, their desired materials and their limitations, and making recommendations based on limitations and budget—often there is a balance that needs to be struck,” he said. For example, he explained, many customers may prefer to prototype various designs in PDMS in order to optimize performance and settle on a conclusive design, before moving on to a more cost-effective material. “One needs to keep in mind the chemistry of what is taking place at each step along the way to suggest surface coatings, different surfactants, etc.,” he continued. “The main element is optimizing the entire system (chip and fluid handling) to achieve the desired performance.”

Another imperative feature of microfluidics is the key to the technology itself: flow control. The microfluidic device on which fluid flow occurs and the equipment controlling the flow are essentially the most fundamental aspects of microfluidics. Numerous solutions for flow control are available, such as pressure controllers and generators, liquid pumps (peristaltic and piezo-electric), electro-osmotic pumps and syringe pumps.  The latter are the most commonly used in microfluidics, due to their flow stability performance, constant mean flow rates, low costs and ease of use. However, syringe pumps can limit fluid dispensing volume and flow rate responsiveness can be rather slow.

“The key is understanding one’s analytical needs, their desired materials and their limitations, and making recommendations based on limitations and budget—often there is a balance that needs to be struck.”

In recent years, alternative flow control techniques have emerged, such as pressure-based solutions. “We use pressure pumps, which can be coupled with flow sensors to give closed loop flow rate control,” said Mr. Gray. “Pressure pumps have fast response, smooth flow, scalability from µL to liter reservoir scale, with flow rate capability from 100nl/min to 500ml/min from the same device. We are developing these systems further to give real time monitoring of performance—such as droplet size—and will then take another step to give real-time control of droplet size and automated detection of fault conditions.”

According to the company, Fluigent was the first to introduce flow control driven by pressure, and, as Mr. Pelletier noted, has numerous patents on methods to optimize pressure control of fluid flow. “The major limitations of syringe pumps for microfluidics are their pulsatility from the stepper motors at low flow rates and slow response time to microfluidic systems that often have a high degree of resistance,” he explained. “The use of air pressure to drive flow eliminates the pulsatility, due to there being basically no moving parts. As pressure changes can be made virtually instantaneously, one can change a flow rate in a matter of milliseconds, where syringe pumps can take several minutes to reach a stable flow.”

Looking Forward

As microfluidics OEM companies, Dolomite and Fluigent focus on supplying their customers with what they need to accelerate their research, with the companies both conducting their own R&D for new techniques and applications that microfluidics can be used for, as well as manufacturing and customizing microfluidics components based on customer demand. “For our end user/laboratory products, we are continually developing new technologies and applications to drive the business forward,” said Mr. Pelletier. “The other main part of our business is in providing OEM solutions for customers needing pressure-based flow.”

Dolomite also works in tandem with its customers, though it has been taking a greater role in the research aspect recently. “Increasingly, we are leading the R&D to offer new capability and applications to our customers, i.e., we have established a Particle Engineering Team to offer new particle generation systems and chemicals, and can do in-house testing of customer samples to validate methods and protocols,” Mr. Gray explained. “However, we still work with scientists every day, to engineer and fabricate custom devices to meet their needs.”

Microfluidics has great potential to be used in a vast array of industries, such as the burgeoning precision medicine industry, in which the accuracy and efficiency of microfluidics can have a major impact. Novel applications utilizing microfluidics continue to emerge, such as RedShiftBio’s AQS³pro (see IBO Spotlight), which uses microfluidics for protein characterization analysis. Bruker’s recent acquisition of Sierra Sensors (see Executive Briefing) also points to advances in the technology, as Sierra Sensors combines SPR with microfluidics.

“I think that microfluidics is perhaps more deeply entrenched in areas of medicine and biomedical research than may be outwardly apparent, and with significant economic impact.”

However, microfluidics technology is not as widely adopted as it seems it should be. Mr. Gray pointed to specific issues that may be limiting wider implementation of the technology. “The two primary constraints are: first, a perceived limit of throughput (how can I make a kilogram of drug delivery particles with a microfluidic chip?), and second, how does microfluidics enter a highly regulated area such as diagnostics or precision medicine?,” he explained. “[Dolomite has] addressed the first with our Telos technology, and plan to go further still into areas such as cosmetics. The second remains a significant challenge, and I think that the hurdles of FDA compliance and fast-moving diagnostics technologies have made it hard for companies to enter the market successfully. For the moment, Dolomite is focused on applications in other sectors.”

According to Mr. Pelletier, there is a substantial influence of microfluidics in research, although it may not be as clear from the outset. “I think that microfluidics is perhaps more deeply entrenched in areas of medicine and biomedical research than may be outwardly apparent, and with significant economic impact,” he stated. He noted companies such as Bio-Rad, Cepheid, Illumina, Opko and RainDance all have products that are based on microfluidics.

Microfluidic technology shows promise for numerous applications, and may be able to help drive research in various sectors in the future. “There is a lot of development in the point of care diagnostics area that is microfluidically based,” Mr. Pelletier said. “New companies are coming on to the scene constantly that are using microfluidics for the next generations of bioanalytical devices, drug discovery, cancer diagnostics/therapy, water testing, bacterial detection, protein analysis and more.”