The latest wearable product of Apple, the Apple Watch Series 6, features a new function that can monitor users’ blood oxygen saturation, which is a critical indicator of people’s overall wellness. The function marks a milestone of wearable devices and is likely to drive demands for sensing components including LEDs and photodiodes.

(Image: Apple)

According to TrendForce, most wearable devices measure biometric data, such as heart rate, blood oxygen, blood pressure, and blood sugar levels, as well as sweat content, through a type of optical technology known as photoplethysmography (PPG).

These sensing product design usually consists of a transmitting end and a receiving end. PPG transmitters measure heart rate via detecting the amount of blood flowing through the user’s wrist for a given duration, generally by using green LEDs paired with infrared LEDs. On the other hand, pairing infrared LEDs with red LEDs will allow these transmitters to obtain blood oxygen levels by measuring the difference between oxygenated and deoxygenated hemoglobin for a given duration. Meanwhile, receivers are designed to feature low dark current photodiodes, which provide fast response times and are capable of receiving the total energy emitted from the LED.

(Image: Apple)

The sensor equipped by Apple Watch 6 is made up of four LED clusters and four photodiodes. Green, red and infrared LEDs emit light onto the blood vessels in the wrist and photodiodes measure the amount of reflected light. These date will then be calculated via algorithms to learn the color of the blood to suggest the oxygen level.

TrendForce estimates that the shipment of Apple Watch in 2020 will grow by 3.7% YoY to 27.7 million units. The rising shipment will also lead to hiking demands for sensing components. The supply chain including module providers Universal Scientific Industrial and STMicroelectronics, LED suppliers Osram and Epistar as well as the photodiode maker Optotech.