Users of Apple Watch have found that their inked skin confuses the sensors on the underside of the devices, and makes it harder for the device to perform certain functions such as reading heartbeats.

Many early buyers of the watch, which was launched on the market last week, have expressed their frustration on social media sites like Reddit and Twitter under the hashtag #tattoogate.

One anonymous user on Reddit - an entertainment, social networking and user-generated news website - said the device's locking mechanism, which should disengage when the watch detects it is being worn, failed to work on decorated skin.

"My hand isn't tattooed and the Watch stayed unlocked. Once I put it back on the area that is tattooed with black ink, the watch would automatically lock again," the user wrote.

Blocking light

Tattoos may also impact the functioning of Apple Watch's heart rate sensors, Apple admitted. On its support page, the company said the device used green LED lights paired with light-sensitive photodiodes "to detect the amount of blood flowing through your wrist at any given moment."

"Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings," Apple added on its support page.

The tattoo issue comes after the Wall Street Journal (WSJ) reported on Wednesday about flaws in the device's taptic engines, which produce the sensation of being tapped on the wrist.

The report said the problem had been detected in some of the parts supplied by AAC Technologies Holdings based in Shenzen, China. Quoting an Apple source familiar with the problem, WSJ said Apple was now looking to a Japanese company to supply flawless parts.

In a survey conducted by Ipsos and Reuters in March among nearly 2,500 Americans, only 24 percent of participants were interested in buying the Apple Watch, while a whopping 69 percent said they were not interested in purchasing the device. Some 7 percent were undecided.

sri/uhe (Reuters,dpa)