On December 13th, 2023, I attended a Watson Lecture at Caltech. These lectures are public talks where scientists share their latest work. This particular lecture was given by Wei Gao, a professor at Caltech who works on biosensors.
Biosensors are devices that can analyze sweat to give real-time health information. Sweat contains a lot of useful information like:
- Metabolites: Things like amino acids and THC.
- Nutrients: Elements like sodium (Na+), potassium (K+), and glucose.
- Hormones: Chemicals like cortisol and insulin.
- Proteins: Substances like albumin and globulin.
- Medication Levels: Amounts of drugs like antidepressants and methadone.
- C-reactive Proteins (CRPs): These are markers often linked to inflammation.
- Ions: Elements like sodium (Na+), potassium (K+), chloride (Cl-), magnesium (Mg2+), and calcium (Ca2+) ions.
These are some examples of information sweat contains. There are much more, but these are some of the most abundant and important components of sweat which can potentially save someone’s life.
Professor Gao talked about the challenges in making biosensors. These include:
- Making high-quality biosensors that can be produced in large numbers.
- Making biosensors that can make you sweat without needing to exercise.
- Making biosensors that can monitor a wide range of very low levels of important biomarkers.
Sweat is a treasure trove of information about our body’s condition. But, unlocking this information isn’t easy or cheap due to the complexity of sweat. Professor Gao’s team has found a way around this by using laser-engraving to create multimodal microfluidic wearable sensor patches at low cost. These patches, made from skin-friendly materials, fit comfortably on the skin.
The sensors work by analyzing sweat. But we don’t sweat all the time, especially when we’re idle. So, how do these sensors work when we’re not sweating? The answer lies in a technique called iontophoresis. It uses a small electric current to stimulate sweat production. A miniaturized iontophoresis module is integrated in the biosensors. This allows for a steady, mild sweat, enabling the sensors to work efficiently, even when we’re asleep.
However, there’s another challenge. The levels of biomarkers in sweat can vary greatly from person to person. To tackle this, the wearable biosensors are equipped with highly sensitive detection mechanisms. These mechanisms can detect and measure specific molecules in sweat, providing a broad spectrum of biomarker monitoring. Professor Gao’s team has developed biosensors based on bilayer MoS2 back-gate FET. The sensors are often integrated into a microfluidic system that can efficiently sample and analyze sweat.
Professor Gao’s team has made several types of biosensors that measure different components of sweat and can help prevent specific diseases. Here are some of them:
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Sweat Biosensors: These devices analyze sweat to track important health measures like metabolites, nutrients, hormones, proteins, and medication levels. They help in real-time health monitoring and early diagnosis.
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Biosensor for Fertility Hormones: This wearable device measures fertility hormones in sweat. It uses a combination of microfluidics and emerging electrode technology with a group of molecules called aptamers to measure hormone levels in real-time.
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Biosensor for Inflammation: This sensor wirelessly detects the presence of C-reactive proteins (CRPs), a marker of inflammation, in human sweat. CRPs are typically present in very low concentrations, so the way Gao’s team measures CRPs is impressive.
One of the most interesting parts of his talk was about how these biosensors are powered. Gao mentioned that these devices are self-powered. They use human sweat to power themselves. The sweat itself has ions and other chemicals which produce small amounts of power. The sensors use power (measured in nanowatts), which is why the power produced from sweat can power the sensors. I’m really excited about the future of these biosensors and the way they harness energy from sweat itself.
The lecture ended with a Q&A session, followed by some time for conversation. It was a fascinating look into the future of personalized medicine, and a testament to the exciting work being done in the field of science and technology.
