As per a new patent filed with the US Patent and Trademark Office, Apple is looking into the option of making its future Watch thinner by removing the haptic feedback engine altogether.
But since the haptic feedback is essential to the user experience, the company wants the battery itself to take over that role. It describes a "moving battery component" that provides the haptic feedback.
By removing the vibration motor, Apple might free up some space and make the battery itself bigger and ultimately improve battery life. Or the manufacturer has some other plans to utilize the free space. Then again, the patent might not even materialize into a final product so only time will tell.
https://www.gsmarena.com/apple_might_use_the_battery_as_a_haptic_engine_in_its_future_watches-news-47477.php