What is Microfluidics?
Before we get into micromachining microfluidic chips, we have to discuss the fundamentals of microfluidics. Microfluidics is the science of how fluids can be measured through microchannels. The field combines chemistry, physics, engineering, biology, and biotechnology principles to help with innovation in various industries and applications. There are three main medical applications used for microfluidics. Diagnostics are used in health care to diagnose viruses, glucose levels, and blood testing, among other tests. The second is biological and uses lab-on-chip devices for drug testing, DNA analysis, and disease detection. The third application is the delivery of medicine in a controlled manner to a patient.
Part of the construction consists of plastic plates called chips that can be manufactured in multiple ways. For example, photolithography, acid etching, molding, and micromachining are the most common methods. These plastic chips are placed within a device that pumps the fluid through the channels and controls the amount of fluid through each channel. Chips are made from a wide variety of materials such as Polystyrene (PS), Polyether Ether Ketone (PEEK), Polyethylene Terephthalate (PET), Polyvinyl Chloride (PVC), Polymethylmethacrylate (PMMA), Cyclic Olefin Copolymer (COC), Polycarbonate (PC), Polyetherimide (PEI) and Pethylsiloxane (PDMS).
Plastic chips are often referred to as a “lab on a chip.” A good example is the COVID test. You apply a fluid to the device and receive results or data without sending it to a lab. This is similar to how testing evolved during the early stages of the pandemic. Another term in microfluidics is “organ on a chip,” which involves replicating the functions of an organ on a small chip for testing purposes. This allows laboratories to study how a disease affects an organ, helping them determine potential treatments to reduce the disease’s impact.
The Benefits of Microfluidics
The significant benefit of microfluidics is that you use fewer fluids for testing. Fluids react differently in smaller amounts so that you can get more accurate and quicker results. The smaller amounts also give you more control over the entire process. Typically, the plastic chips used in microfluidics are translucent so that the fluidics can be viewed through a microscope. One of the main advantages of microfluidics is you can do lab-type work within your small business without having to send it out to a lab, saving you time and outsourcing costs.
How to Manufacture a Microfluidic Chip?
There are four ways to produce a microfluidic chip, each with advantages and disadvantages. Methods include: photolithography, acid etching, molding, and micromachining microfluidic chips.
Photolithography
The main advantage of photolithography is that you can produce very fine channels that might otherwise be impossible due to the tooling size required in a machining process. The downside of photolithography is that you must go through several methods to achieve your final part. It also involves a lot of different equipment for each step, costs money to purchase and maintain the equipment, and consumes valuable floor space. Due to the larger number of steps in the photolithography process, takes extra time and requires different skill levels for each stage, which often means using multiple people for each stage. Considerations such as temperatures and having a proper vacuum make this more complicated than micromachining.
Acid Etching
Acid etching can also be used to create the chip, and it has advantages and disadvantages similar to photolithography. However, due to the hazardous chemicals required in the etching process, the photo method is typically more common than the acid etch process.
Molding
The main advantage of the molding process is you can produce high quantities of the same chip design quickly and cost-effectively. The challenge with molding is you first need to create a mold. The mold either needs to be outsourced at a high cost or requires special equipment and expertise to produce in-house. The molding process can be either injection molding or a hot stamp die. If you need a high volume of chips that are precisely all the same or there is little risk you will require design changes, molding is a good solution.
Micromachining Microfluidic Chips
Micromachining of plastic chips offers the most flexibility. You can do one-off R&D-type parts quickly or run small production batches with low-cost efficiency. You also have the option to do high-volume runs and avoid making the investment cost of creating a mold. The milling process can create a smoother texture within the channels with better control over the channel size than the other manufacturing methods. This significantly impacts the accuracy of the test results. Micromachining allows you to do three-dimensional milling that photolithography cannot, offering more fluid testing capabilities and advantages. The cost of producing the part in micromachining is less than that of the photolithography process and can be done faster. Micromachining is becoming common for making R&D and small to medium-batch production quantities.
Watch a DATRON M8Cube Mill an Acrylic Microfluidics Plate
10 Reasons Why You Should Use a DATRON for Micromachining Microfluidic Chips
#1) Highspeed Spindle
Due to the small, detailed channels required in the micromachining process, a machine tool with a high-speed spindle is critical to the efficiency of the process. Milling with small tools needs to be spun at higher speeds to achieve a shorter machining time. Equipment with low RPMs (for example, 10,000 RPM) using small tools must travel very slowly through the material, or the cutting tool will break. This can mean a very lengthy time to machine a part. DATRON uses spindles that reach 60,000 RPM, often producing a part in minutes compared to hours spent using a traditional machine tool.
#2 Non-machinist Can Operate
Machine tools to produce microfluidic chips are often found in a lab environment and are preferred to be operated by scientists, not machinists. The interface to the equipment must be simple, intuitive, and easy to operate. Traditional machine tools have complicated controls, with many push buttons and dials. Machines are generally operated only by experienced machinists. DATRON takes a different approach to our machine interface. DATRON’s next Control Software is very similar to a smartphone or tablet and uses familiar touchscreen gestures, menus, and visual icons, making it easy to learn and operate. DATRON often sees non-machinists fully operating a machine just a few days after installation
#3) X, Y Part Accuracy
In microfluidics, it is critical that the milled channels are precise and within tolerance. Therefore, this application requires a machine tool with precision tolerances and depth control. Most compact benchtop machines do not offer the accuracy needed.
The German-engineered DATRON system achieves the precision required for this process by evidence of many labs, universities, and manufacturers currently using the equipment. Features such as dynamic milling will maintain tolerances and surface finishes within a channel if the cutting path must decelerate to go around a corner or accelerate as it comes out of one. Heavier machine tools cannot achieve this due to the weight of the spindle Z axis and need the agility that DATRON offers on our machines. DATRON also provides a linear scale option for very tight-tolerance microfluidic applications. It is a precision reference guide or ruler-like scale monitored by a laser. This gives feedback to the machine control to its actual location, and the motion control system will compensate for any variance at a micron level. This option is ideal for microfluidic applications like sputtering centrifugal discs, often requiring tight micron-type tolerances.
#4) Thermal Growth
Features such as a chiller that pumps refrigerant around the spindle bearings help maintain a constant temperature of the spindle, reducing any thermal movement or growth in the Z-Axis. Without a chiller, the spindle temperature would change, and the materials used to construct the spindle would expand as the spindle heats up. This would change the location of the cutting tool in the part, impacting your channel depth tolerances. DATRON offers chillers for our highspeed spindles in applications requiring tight tolerance cutting depths.
#5) Precision Channel Depths
Typically, the supplied plastic sheet material is consistently different throughout a sheet. This can lead to inaccurate channel depths throughout the material because of the variances in the material. Machining the material to an exact thickness takes time and obtaining a quality surface finish can be difficult. With the DATRON system, an optional integrated probe can be added to the machine and programmed to measure a matrix of points over the entire surface of the sheet. The machine control then takes this data and raises and lowers the spindle to follow the material variances.
You, therefore, can program your chip as if the material is perfectly flat, and the machine will automatically raise and lower the spindle when it knows the material is thicker or thinner in certain areas. There is no need to take time to prepare your material. You will also have lower part rejection rates because your machining depths will be within tolerance, regardless of material thickness variances.
#6) Precision Tool Lengths
To ensure precise channel requirements, your tool offset (the recorded length of the cutting tool) must be accurate. This process is done manually on many low-cost or tabletop systems, which can be time-consuming and prone to errors. Incorrect measurements can result in out-of-tolerance parts. However, with the DATRON system, the operator can quickly and precisely measure the cutting tool length via a touchscreen command in seconds during tool setup. Additionally, programming the machine to automatically touch off the tool after each tool change helps to compensate for cutter wear and achieving micron-level accuracy.
#7) Material Mounting
Plastic microfluidic chips are typically a flat material that can be difficult to secure to the machining table. The large, often thin sheet size does not lend itself well to mechanically securing at the edges. Doing so can usually distort the material and create a domed effect. Typically, they are double-sided and taped to a plate. This process takes time to set up and remove and can leave adhesive residue that could contaminate the testing process. DATRON uses a unique vacuum table system that precisely and positively secures the material in seconds without using tape or fasteners. The setup of your part takes seconds, and it holds your material flat and securely over the entire sheet.
#8) Customized Cutting Tools
Many generic cutting tools are not ideal for machining plastics because of their design to handle a wide range of materials, including steel. In contrast, DATRON provides a line of micro-grain carbide tools optimized explicitly for machining microfluidic chip materials. These tools feature specialized cutting geometries that enable high-speed machining in plastics while delivering superior surface finishes, which are essential for microfluidic applications. Additionally, DATRON offers MCD tools with diamond cutting edges, which can surface materials and produce an almost optically clear finish.
#9) Clean Room Ready
Clean rooms have various levels or classifications depending on lab requirements. Many machine tools are unsuitable for clean rooms because they use lubricants and coolants that can cause contamination. However, many DATRON customers have successfully installed their machines in clean room environments. DATRON machines are fully enclosed, protecting the exterior from contamination. In some cases, installing the machine can be done without any modifications. Still, depending on your specific needs, you might need to use a different lubricant. You should consult with DATRON to ensure your exact requirements are met.
#10) Footprint
It is common to find labs confined on an upper level of a building complex and crammed with equipment. Floor space can be a scarce commodity. These spaces usually cost more per square foot due to their location in comparison to factory floors in industrial communities. Traditional machine tools are large, heavy, and bulky to install in a lab environment. Smaller desktop-type CNC machines often don’t offer the tolerances and features required for this application. DATRON provides the best of both worlds. For example, the compact DATRON neo can fit through a standard doorway. The neo does not take up any more floor space than a refrigerator, and can be installed on the upper floors of an office complex because of the machine’s light weight design. Yet, it offers the accuracy and reliability of a much heavier traditional machine tool.
DATRON has Your Micromachining Microfluidic Chip Solutions
Micromachining microfluidic chips has become essential for various medical and scientific applications. From diagnostics to drug testing and disease research. As the demand for high-precision, low-volume production continues to grow, choosing the right manufacturing method is crucial. Among the options available, micromachining stands out for its flexibility, cost-effectiveness, and precision. It is ideal for both R&D and small to medium production runs.
DATRON’s advanced machining technology, with its high-speed spindles, intuitive controls, and tight-tolerance capabilities, offers a streamlined solution for creating microfluidic chips with exceptional accuracy and speed. By simplifying complex processes and reducing setup time, DATRON systems provide a reliable, clean-room-ready option for labs and manufacturers looking to scale their microfluidic production without sacrificing quality. Contact our knowledgeable team today to learn more!
