The past several years have seen an acceleration in research and product development in a multitude of fields. Though there are many factors involved, what has been most impactful in these technological leaps is the equipment used to conduct such experimentation, with the advancement in microfluidics leading the way. Microfluidic devices, often referred to as microfluidic chips, are revolutionizing fields such as biomedical research, diagnostics, and chemical analysis [1].
Microfluidic devices are designed to manipulate tiny volumes of fluids using precise micro-scale channels, essentially shrinking the traditional laboratory into a space that can fit in the palm of your hand [2]. These devices not only accelerate research but can be specifically designed through the choice of their construction materials to directly impact their performance, durability, and application range.
Introduction to Common Materials for Microfluidic Device Fabrications
Also known as lab-on-a-chip systems, microfluidic devices can integrate an array of laboratory functions onto a single chip. Their precision allows for the testing for a variety of applications including drug development, DNA analysis, and point-of-care diagnostics [3]. The core of these devices is built through a fabrication process involving the creation of microscale channels and chambers in which fluids can be precisely controlled and manipulated.
Key Materials for Microfluidic Device Fabrications
1-Polydimethylsiloxane (PDMS)
What is PDMS? The materials used to construct these devices require specific qualities such as flexibility, transparency, and biocompatibility [4]. PDMS, a silicon-based organic polymer renowned for encompassing these attributes, stands out as one of the most extensively employed materials for fabricating microfluidic devices.
Advantages of PDMS:
- Flexibility: PDMS is highly flexible, making it suitable for creating intricate microfluidic designs.
- Transparency: Its optical transparency allows for easy observation of fluid flow as well as the reactions within the chip.
- Biocompatibility: PDMS is non-toxic, meaning that it will not cause damage or contamination, and is suitable for biological applications.
- Gas Permeability: It allows gases like oxygen and carbon dioxide to diffuse through, beneficial for cell culture applications [5].
Applications of PDMS:
- Microfluidic Product Development extensively uses it due to its ease of application in prototyping fabrication.
- PDMS Casting and Molding enables rapid microfluidic device production because of its malleability qualities.
- Lab-on-a-Chip Manufacturing commonly uses it in creating lab-on-a-chip devices for biochemical assays and cell biology studies because it meets all the needs of microfluidic device construction [6].
2-Glass
Advantages of Glass:
- Chemical Resistance: Unlike many plastics and other materials, glass is highly resistant to solvents and reagents, making it ideal for chemical analysis applications.
- Thermal Stability: Extreme heat can warp other materials; however, glass can withstand high temperatures, useful for thermal cycling processes such as PCR.
- Transparency: As would be expected, it has excellent optical properties for real-time observation and imaging [7].
Applications of Glass:
- Microfluidic Chip Manufacturers: Because certain chemicals can be challenging to work with in terms of resistance and optical clarity, glass is often the preferred material for certain applications.
- Lab-on-a-Chip Devices: Often used in high-precision analytical instruments and diagnostics [8].
Also Check Out: Advantages of Microfluidics Devices
3-Polymethyl Methacrylate (PMMA)
Advantages of PMMA:
- Cost-Effective: Cost is often a factor when considering testing. PMMA is less expensive than glass and silicon.
- Easy Fabrication: Being that it is a highly flexible material, it can be easily machined or molded into desired shapes.
- Optical Properties: It is clear, allowing for easy visualization [9].
Applications of PMMA:
- Disposable Devices: Some agents require fresh devices. PMMA, due to its lower cost, is commonly used for disposable microfluidic chips in point-of-care diagnostics.
- Prototyping: Suitable for rapid prototyping due to its ease of processing [10].
4-Polycarbonate (PC)
Advantages of Polycarbonate:
- Durability: When strength is a priority, PC is often the choice, as it is mechanically strong and resistant to impact.
- Thermal Resistance: It can also withstand a range of temperatures, suitable for various experimental conditions.
- Biocompatibility: Safe for use in biological applications [11].
Applications of Polycarbonate:
- Reusable Chips: Because of its strength and resistance qualities, it is often used for reusable microfluidic devices.
- Medical Devices: Employed in the fabrication of medical diagnostic tools.
5-Silicon
Advantages of Silicon:
- High Precision: Some applications require higher accuracy. Silicon allows for precise microfabrication using photolithography and etching techniques.
- Thermal Conductivity: Excellent thermal properties for heat-sensitive applications.
- Integration with Electronics: Many fields require testing applications that are geared toward electronics. Silicon easily integrates with electronic components, which makes it useful for sensors and detectors [12].
Applications of Silicon:
- Integrated Systems: Used in complex microfluidic systems that require electronic integration.
- High-Precision Analysis: Ideal for applications requiring high precision and stability [13].
6- Paper
One of the greatest advancements in microfluidic device construction is based on one of the most simple and basic materials. Paper microfluidics take advantage of the natural and unique porous structure of the cellulose fibers in paper:
Advantages:
- Low-cost: Paper is readily available and inexpensive, making it ideal for resource-limited settings.
- Disposable: Used paper devices can be easily discarded, reducing the risk of contamination, as well as lowering cost.
- Simple fabrication: These devices can be fabricated using techniques like wax printing or inkjet printing, making them accessible for even basic laboratory setups [14].
Applications:
- Paper microfluidics is particularly attractive for point-of-care (POC) diagnostics. POC devices allow for rapid and on-site testing, which is crucial in areas with limited access to sophisticated medical facilities. Examples include pregnancy tests and tests for infectious diseases [15].
7-SU-8
If ultra-accuracy is of critical importance, SU-8 takes us into the realm of high-precision microfluidics:
Properties:
- High Resolution: SU-8 can create very fine features with high detail, enabling complex microfluidic designs with intricate channels and structures.
- Excellent Chemical Resistance: SU-8 is resistant to many chemicals commonly used in microfluidic experiments, making it suitable for applications involving harsh environments.
Applications:
- SU-8 is commonly used for creating microfluidic molds for other materials like PDMS. Due to its high resolution, it’s ideal for devices with intricate microfluidic features or those requiring precise control over fluid flow [16].
The Future of Microfluidic Materials
Even with the amazing advancements in microfluidic technology, innovation in materials used to construct these devices is an ongoing process. Researchers are continuing to explore new materials like hydrogels that can mimic the properties of human tissue, and breakthrough composites that combine the strengths of different materials. As the microfluidics field progresses, more versatile and sophisticated materials will emerge, increasing their capabilities as well as their applications.
