Yesterday’s report that we might see Apple Watch blood sugar monitoring when Series 7 releases this year has sparked both excitement and skepticism.
Excitement, because it could provide a much simpler method of monitoring blood sugar than current devices, which require a blood sample per prick. Skepticism because non-invasive measurement has been a goal for many years, with very limited success to date. The closest we have so far is a rice grain-sized sensor embedded in the skin which can then be read without further puncturing the skin …
Traditional blood glucose monitors require the patient to use a needle stick device to collect a drop of blood and transfer it to a test strip, which is then read by a machine. The process is not ideal: it is very slightly painful, somewhat complicated, and requires a steady supply of test strips.
For this reason, many companies have tried to develop monitors that are non-invasive, that is, monitors that do not require a drop of blood.
A developing form of non-invasive measurement uses the thin flap of skin between the thumb and forefinger.
Glucose levels are extracted by a non-invasive technique that transmits low-power radio waves through a section of the human body, such as the area between the thumb and forefinger. These areas have an adequate blood supply and are thin enough for the waves to pass through the tissue. These signals are then received by a sensor on the opposite side of the GlucoWise device, where data on the characteristics of blood in the flesh is collected and analyzed.
But, as the explanation explains, it only works because the skin is very thin there. How could an Apple Watch measure blood sugar on the wrist?
The answer may lie in an approach outlined in Nature in the summer of last year. A skin tag – much like an RFID – is stuck to the skin and then fed by a reader built into the Apple Watch.
This article reports a highly sensitive non-invasive sensor for real-time blood glucose monitoring from interstitial fluid. The structure consists of a tagless tag sensor that can be stuck on the patient’s skin and a reader, which can be integrated into a smart watch.
The tag sensor is powered by the electromagnetic coupling established between the tag and the reader and its frequency response is reflected across the spectrum of the reader in the same way. The tag sensor consumes no power as there is no need for an active read or communication circuit on the tag side […]
The sensing element itself is just a metallic trace which could be simply stuck to the patient’s skin and which is replaceable at extremely low cost […]
When measuring changes in glucose concentrations in saline-replicating interstitial fluid, the sensor was able to detect glucose with an accuracy of approximately 1 mM / L over a physiological range of glucose concentrations with a 38 kHz shift of resonant frequency. This high sensitivity is achieved by the proposed new design and an extended field concentration on the label.
It works by measuring the change in radio frequency. This shift is proportional to the relative percentages of water and glucose in the blood.
This frequency is selected because there is a considerable difference between water, as the main material in the interstitial fluid, and the permittivity of the saturated glucose solution while their loss factors are still low, and therefore measure at this frequency will cause a significant frequency offset and hence the sensitivity of the device.
We illustrated yesterday how the results could be displayed on the watch.
There are also infrared approaches in development, which could potentially work with existing Apple Watch models, but the above approach seems more promising in terms of accuracy.
All of this remains highly speculative, however. The method should be evaluated and approved for use, and it appears that this technology is at a very early stage in this process. While I think we’ll likely see this in the Apple Watch at some point, the timing seems tight for a Series 7 release.
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