Low-power Integrated Circuits for Wearable Chemical Sensors
Problem being addressed
Wearable devices are very popular for gathering data about ourselves for healthcare and fitness activities, but currently they can only monitor electrical signals such as heart rate or general activity. To obtain a deeper insight into physiology, it is helpful to look at your body chemistry. Typically, this would require a blood test or urine sample which can be invasive or painful, however, there is opportunity to obtain equally useful information in other bio-fluids such as sweat. Sweat is an easily accessible bio-fluid rich in ions, metabolites and other chemicals which can help us understand what's going on inside the body, continuously and non-invasively. Recent advances in low-power microchip technology means that these measurements can now be carried out in wearable devices, enabling the next generation of wearables.
Using standard microchips - the same technology found in all smartphones - we can create tiny, low-power and low-cost electrochemical sensors. The sensors are built into the microchip itself, by modifying a widely used electronic component to become sensitive to the electrical charge of ions (such as Hydrogen (pH), Sodium or Potassium) in a target solution. By integrating sensors and processing onto a single chip of just a few square millimeters, the full device takes up a very small amount of space and so can be worn in an unobtrusive patch on the skin.
Advantages of this solution
A common alternative method used in wearable sweat sensors is to use ion selective electrodes (ISEs). These are conductors which can be screen printed on a small scale, however they then still have to be connected to an electronic system to process the signals they detect. Using our method, the sensors are integrated into the chip itself, reducing area required along with manufacturing steps that can reduce cost, and improving signal robustness by minimising the distance between sensor and processor. On top of that, the sensors themselves roughly take up an area of 10s of square micrometers. While ISEs can also be fabricated on this scale, the integrated approach easily allows massive arrays to be produces on a single chip, just like pixels in a camera, enabling potentially 1000s or more sensors on a single device. This gives the opportunity to improve signal quality and detect multiple different targets simultaneously.
Possible New Application of the Work
With accurate inference of physiological state, you could feasibly determine a users need for hydration drinks, or perhaps affinity for exercise and lifestyle choices.
Small discrete electrochemical sensors could potentially be used to monitor soil health, or plant / produce quality.
Integrated electrochemical sensors are currently being used to diagnose infectious diseases in developing countries, and to detect particular DNA mutations for determining a users predispositions.
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