Make-Your-Own Microfluidics Device

Research Question:

How can we use very simple components to make a microfluidic device capable of making a quantitative colorimetric measurement?


Watch the videos to the left on using toys and household items to hack healthcare!

Learning Objectives:

  1. Determine the different design elements necessary to produce a successful lateral flow microfluidic device and explain why they are important.

  2. Use data from an experiment to iteratively design and conduct subsequent experiments.

  3. Design a lateral flow device that can produce quantitatively reliable results.

  4. Explain how intermolecular forces are involved in the production and use of lateral flow microfluidic devices.


To Do List:

Step 1: Read lab background, watch videos, and visit links provided about experimental context on this page (scroll down on this page)

Step 2: Read lab procedure

Step 3: Watch corresponding lab tutorials

Step 4: Answer pre-lab questions

Step 5: Perform lab experiment

Step 6: Answer post-lab questions

While microfluidic devices are sometimes complex analytical tools, they can be simple to create from everyday items. Jose Gomez-Marquez, director of MIT's Little Devices Lab, is pioneering the use of toys to make medical equipment. His work includes making microfluidic bioassays using legos and manufactured parts. The team at MIT has used this lego microfluidics technology to develop low cost blood analysis tests.1

Dr. Gomez-Marquez and his team are committed to putting flexible lost cost technology into the hands of people who can use it to develop their own tools and that is precisely what we are going to do in this lab!

The image shows an open medical diagnostics kit containing rulers, eppenndorf tubes of various sizes, a small device constructed from gears, an information packet, and a rectangular plastic device.

Figure 1. Example medical kit made from little devices1

The outline of a five-pointed star is drawn on a piece of filter paper in purple crayon, which has been baked into the paper material. The outline acts as a barrier to contain the liquid inside the star. The star is filled with food-colored water in shades of red, yellow, blue, and purple.

Figure 2. Example of hydrophobic and hydrophilic areas

Paper microfluidics can be even more flexible and easy to use than lego microfluidics. To produce a device, you can use easily accessible filter paper and something as simple as wax crayons to make testing devices for applications such as diagnosing disease and testing soil and water.

The fundamental principle behind this paper-based fabrication technique is the contrast of hydrophobic and hydrophilic areas to create a pattern of of fluid filled areas on paper.2 The pattern can be created by using any type of wax like parafilm, candles, a wax printer or in this case crayons, to outline the fluid channel, then applying heat to the wax so that the hydrophobic substance penetrates the full thickness of the paper. The wax-filled paper creates a hydrophobic boundary for the hydrophilic channel.

The flow of the liquid is driven by capillary action.3 Water, and liquids with similar polarity will maximize their intermolecular forces causing the fluid to wick through the paper. Plants use this same phenomenon to move water and nutrients from soil up stems to leaves. Capillary action can move fluids over a distance of 20 mm within 2 seconds.3 Properties such as viscosity and surface tension of the sample can alter the time it takes for capillary action to wick the sample into a certain area.



Microfluidic devices that make use of wicking are often called lateral flow. One well known example of a lateral flow device is a pregnancy test. The fluid is drawn through the channel into different areas containing the reagents. The reaction takes place in the interstitial spaces between the paper fibers. A colorimetric reaction unique to the assay will occur in the detection zone and can be measured quantitatively using a spectrophotometric probe or a smartphone camera, or semiquantitatively with the naked eye. Watch this video to see more about how pregnancy tests work: How Do Pregnancy Tests Work? | Reactions Science Videos

The image shows a series of square plastic devices linked together at the edges. Small paper strips are threaded though the devices, spanning the links. The arrangement makes the strips spell out MIT.


More recent development in microfluidic technologies shows that various microfluidic channels can be joined together to form a single chip capable of facilitating an entire chemical process from beginning to end, eliminating the need for complex equipment or instrumentation.4

In this lab your goal is to design a lateral flow device that quantitatively mixes different colors to produce a calibration curve. For example, you will mix a series of different concentrations of blue dye with yellow dye to produce a green calibration curve. This lab will involve investigating the different steps of producing, using and detecting color on a microfluidic device.

References

  1. Research – MIT Little Devices Lab. https://jfgm.scripts.mit.edu/littledeviceslab/research-2/ (accessed Jul 22, 2020).

  2. Li, X.; Ballerini, D. R.; Shen, W. A perspective on paper-based microfluidics: Current status and future trends . Biomicrofluidics 2012, 6, 011301-13.

  3. Songok, J.; Tuominen, M.; Teisala, H.; Haapanen, J.; Mäkelä, J.; Kuusipalo, J.; Toivakka, M. Paper-Based Microfluidics: Fabrication Technique and Dynamics of Capillary-Driven Surface Flow. ACS Appl. Mater. Interfaces 2014, 6 (22), 20060–20066. https://doi.org/10.1021/am5055806

  4. Koesdjojo, M. T.; Pengpumkiat, S.; Wu, Y.; Boonloed, A.; Huynh, D.; Remcho, T. P.; Remcho, V. T. Cost Effective Paper-Based Colorimetric Microfluidic Devices and Mobile Phone Camera Readers for the Classroom . J. Chem. Educ. 2015, 92, 737-741.