You Can Count On It
MIT's new smartwatch-sized device tracks blood cells in real-time, bringing a lab-quality blood analysis straight to your wrist.
You have probably heard of complete blood count tests before, but do you know what it is that they are actually counting? It is the number and types of cells that are found in the blood. Running this test is often a first step in assessing one’s general health or diagnosing disease because the results can be very revealing. An abnormally low number of red blood cells, for example, may be due to nutritional deficiencies or internal bleeding, while high levels of white blood cells may signal that an infection is present.
While these tests are frequently performed, they are far from ideal. The patient must first come to a clinic for a blood draw, then the sample must be sent away for analysis at a lab. This is not only inconvenient, but it also introduces a significant delay. Moreover, the blood sampled only provides a small snapshot of the overall picture of one’s health. A much better solution would be to continually monitor blood cell counts throughout the day.
But that is not practical with existing technologies. An instrument like a flow cytometer could do the job, but they are very large and in no way mobile. Or at least that used to be the case. Researchers at MIT have developed a wristwatch-sized device that works on principles similar to those of a flow cytometer. When strapped on the wrist, it can scan beneath the surface of the skin to identify blood cells as they zip by through the veins.
The team’s creation, called CircTrek, directs a laser beam toward the skin. This laser, when focused by an optical system, excites cells that have been labeled with a fluorescent dye. A photodetector called a silicon photomultiplier was utilized to sense the presence of the excited state of the fluorescent dye. An onboard ESP32 microcontroller processes the raw data and translates it into cell counts. The ESP32 also provides Wi-Fi connectivity such that the readings can be streamed to the patient’s physician in real-time. The hardware measures just 42 mm by 35 mm, making it about the size of a typical smartwatch.
So far, the device has been tested in an in vitro experiment that simulated blood flow beneath human skin. The results produced by the device were found to compare favorably with a manual count performed with a high-resolution microscope.
An obvious drawback to using this technology is that it requires cells to be fluorescently dyed. That alone is enough to cause most people to request a traditional lab test. But for certain situations, such as with people receiving CAR T cell therapy, the cells may already be labeled. In these cases, the device could provide valuable insights about the effectiveness of the therapy.
While CircTrek may not yet be ready for widespread clinical use, its development could ultimately lead to more accessible, continuous blood monitoring. By shrinking the capabilities of a flow cytometer into a wearable format, the researchers have opened the door to a future where real-time blood analysis could become part of our everyday health tracking, much like a heart rate monitor is today.