Microfluidic chips are widely used in various fields ranging from medicine, science, and the food industry to environmental engineering. While gravitation plays a major role for liquids at the macroscopic scale, microfluidics are dominated by surface forces. Microfluidic flow is dominated by viscous forces and is laminar. Therefore, liquids behave in a more controlled and predictable way than in a macroscopic system. Numerous techniques enable the fabrication of microfluidic chips, including hot embossing, injection molding, laser ablation, 3D printing, and focused ion beam machining. While a single chip doesn’t allow the change of parts of the implemented microfluidic network, a modular system allows the rearrangement of components by splitting up the network into different parts separated into different blocks or modules. This can be achieved by using LEGO blocks.
Research shows that this approach works for open microfluidic networks. Additionally, when using polydimethylsiloxane (PDMS) as a base material, it can be used to fabricate organ-on-a-chip systems. In this work, Ecker and colleagues aim to create a modular microfluidic system using magnets and casted O-ring-like structures.
Two modular microfluidic blocks (MMBs) can be easily connected and disconnected using magnets. Each MMB contains small magnets; when you bring two MMBs together, the magnets align the connection interface and connect the blocks (Figure 1).
The goal was to produce a transparent module that would allow the visualisation of test fluids inside the channel structures. So, the researchers opted for using PDMS.
The manufacturing process of MMBs involves many steps. Initially, researchers created a template for the MMBs. This template serves as the foundation for crafting a polyurethane (PU) mould, essential for casting the MMBs. After that, PDMS is added to the mould, allowed to cure in an oven, and finally removed from the mould.
Function of the Flow Sensor
The researchers wanted to test if their flow sensor worked properly by comparing its measurements to those of a known commercial flow sensor. To achieve this, they used Cellix's ExiGo syringe pump to set different fluidic flows and measure the actual flow using both their flow sensor and a commercial flow sensor.
The researchers compared the measurements from the MMB sensor to those from the commercial sensor and found they were very similar, confirming the feasibility of the MMB sensor (Figure 2).
Other experiments in this study
The researchers tested some pumps and found they work well up to a certain speed, about 50 Hz. They also tested how well the system was connected by closing most openings, pouring water into the only open one, and measuring the pressure. They found that the system stayed sealed up to a certain pressure.
By using different measurement setups, the authors demonstrated the feasibility of the device.
How to get started
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Ecker, Rafael, et al. "A Self-Sealing Modular Microfluidic System Using PDMS Blocks with Magnetic Connections." IEEE Access (2023).