Mastering the Flow of Tiny Biological Liquids with Electrogates

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Authors of the paper, left to right, O. Gökçe, E. Delamarche, Y. Arango and Y. Temiz.

Today, much of the knowledge we have in biology and medicine is derived from the ability to detect analytes from complex biological samples, such as blood and urine. This knowledge, in the form of data, is vital for patient diagnostics. For more than a decade, IBM scientists have taken their years of experience from the computer industry and applied it towards the development of new bioanalytical tools and techniques to push the frontiers of knowledge in life sciences.

Some of these tools are microfluidic chips that can be used for point of care diagnostics (POCDs). These chips can be about the size of a memory stick and are designed to be used in emergency situations in the field, i.e. on an ambulance truck, to get fast results from patients, who for example could be complaining about chest pains at a restaurant before going into cardiac arrest. Trained medical staff can take a small sample of blood, around the size of a tear, and drop it on the chip where it flows through a series of channels, interacting with reagents along the way, to derive an accurate diagnostic result in seconds. These results can then help doctors determine the right course of action.

However, one of the major limitations of these devices is their lack of flexibility because each chip must be designed and fabricated accordingly to a specific application. For example, the same chip architecture may not be used both to detect cardiac problems and infectious diseases such as malaria, but this is about to change.

Appearing today in the peer-review journal, Applied Physical Letters, IBM scientists in Zurich demonstrate a simple, yet effective technique to address this challenge, which they call electrogates or “e-gates,” for short. The e-gates are precisely designed for the stop-and-go control of the flow of liquids in capillary-driven microfluidic chips. If you have ever dipped a croissant in your morning coffee, you are familiar with capillary-driven flow.

Photograph of a fabricated chip containing 6 independent flow paths and 2 e-gates per path

The key trick to the e-gates are 2 micrometers deep trenches, which are designed in a semicircular pattern and etched at the bottom of 15 micrometer high microfluidic channels — for comparison, red and white blood cells are between 2-5 micrometers wide. This trick allows biological samples to stop at specific positions along the channels so the flow of the liquid can resume precisely by applying a DC voltage between the liquid and the trench. The voltage for each e-gate is conveniently controlled using a smartphone app, providing flexibility and control over the flow conditions.

In one particular design reported in the paper, the IBM team demonstrated that they could stop and start the flow in less than 1 second, using a voltage of 5 V, basically one standard square battery you can buy at the store, making the e-gates particularly compatible with portable, low-power tests. This simple concept is very efficient and can get samples going where and when needed in various parts of a chip to optimize tests independently from each other while keeping microfabricated chips very generic.

In summary, our approach uses a simple geometrical pattern, which can easily be fabricated using techniques that are already compatible with many POCD devices employing microfluidics and electrodes. The next step for the research is to look for partners to license the technique and bring it to market.

This work has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. [701690].

Electrogates for stop-and-go control of liquid flow in microfluidics, Y. Arango, Y. Temiz, O. Gökçe and E. Delamarche

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