Apple developers, in the build up to the launch of the new smartwatch, have outlined one group who might not get the most out of their new product – anyone with a tattoo.

The smartwatch has many functions which operate by light sensors on the watch’s back, which may be interfered with by dramatic changes in skin tone such as darker tattoo ink. The ink of some tattoos can block light from reaching the sensor, making functions such as a heart rate sensor prone to failure and misreading.

The watch works by using green LED lights to detect the amount of blood flowing through the wrist, which as Medicine and Natural Biological Sciences applicants will know is how the heart rate is measured at the wrist. Further to this problem, another investigation by Reuters has found that the soft ping signals that alert a user to an incoming message do not work on people with tattoos where the watch is worn. Fundamentally, ink on the wrist makes it difficult for the watch to detect that a wrist is there at all.

This problem is not, however, unique to Apple. Many sensor-based technologies have found failures with not only tattooed skin, but darker skin in general. The amount of light reflected back from darker pigmentations of skin is typically less light than the technology is designed to cater for. Engineering applicants should explore further on why it is important to ensure technologies are fit for purpose across large and diverse sample sizes, and HSPS applicants should explore further on how and why consumer products cater to majoritarian groups.

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