Imagine that you are sitting in a cafe leisurely, and the coffee in your hand exudes an attractive aroma. You don't need heavy instruments, and you don't have to endure the pain of needles, so you can know your blood sugar level in real time. Does this sound like science fiction? Today, this is not a distant dream. A technology called "non-invasive blood glucose monitoring" is quietly changing the lives of diabetic patients and pushing the traditional blood sampling monitoring to the edge of history.

The traditional blood glucose monitoring relies on blood sampling at the fingertips, and the glucose concentration in the blood is analyzed by a blood glucose meter. Although this method is accurate, frequent blood collection not only brings pain and inconvenience to patients, but also makes it difficult to achieve all-weather continuous monitoring. Non-invasive technology, on the other hand, has turned its attention to a wider field, from sweat, tears and saliva to skin tissue and even electromagnetic waves.

One of the most potential directions is technology based on optical principles. It uses light with a specific wavelength to penetrate the skin and interact with glucose molecules in subcutaneous tissue, and infers the blood glucose concentration by analyzing the changes of reflected or transmitted light. For example, a technique called "Near Infrared Spectroscopy" uses light in the wavelength range of near infrared light to penetrate the skin for several millimeters to measure the glucose absorption of subcutaneous tissue. This method does not need blood collection, and can be made into wearable devices, such as smart watches or bracelets, to realize real-time continuous monitoring. Its challenge is that the temperature, moisture, pigment and other factors on the skin surface will interfere with the measurement results, and complex algorithms are needed to correct them.

Another striking direction is the use of microwave or radio frequency technology. This sounds more like a plot in a science fiction movie. By emitting low-power microwave signals to the skin, these signals will resonate with water and glucose molecules in the body. Different concentrations of glucose will affect the dielectric constant of water molecules, thus changing the reflection or transmission characteristics of microwave. By accurately measuring these changes, the blood sugar level can be calculated. The advantage of this technology is strong penetration and little external interference, but it also needs sophisticated hardware and complex signal processing technology.

In addition to physical methods, non-invasive technologies based on biochemical principles are also developing. For example, using the microneedle patch, this tiny needle is only a few tens of microns long, which is thinner than the hair, and the user can hardly feel the sting. These microneedles can pierce the outermost stratum corneum of the skin and come into contact with interstitial fluid. The glucose concentration in interstitial fluid is highly correlated with the glucose concentration in blood. The enzyme coated on the microneedle will react with glucose to generate an electrical signal, which will be captured by the sensor. Although this technology has a "needle", its painless and minimally invasive characteristics make it closer to the scope of non-invasive monitoring.

The development of these technologies is far from smooth sailing. Every direction faces unique challenges. How to ensure the accuracy and stability of the measurement results, how to eliminate all kinds of interference factors, how to make the equipment smaller and more comfortable, and how to reduce the cost are all difficult problems that scientists and engineers are trying to overcome.

In the future, non-invasive blood glucose monitoring devices may be as popular as smart phones. They may be integrated into our smart watches, glasses and even contact lenses. Diabetic patients will no longer need to carry blood glucose meters and test papers with them, and they will no longer have to endure the pain of blood collection many times a day. They can know their blood sugar changes anytime and anywhere and manage their health better. This is not only a technological innovation, but also a great improvement in the quality of life, which will bring hope to countless people and open a brand-new era of health management.

（Writer：Juliy）