Apple first revealed their work on bringing a hydration tracking system to Apple Watch back in August 2021. Apple noted back then that hydration measurement capabilities described in their patent provided reliable and elegant solutions that would allow a user to easily track hydration with a wearable electronic device, such as an Apple Watch, and provide helpful feedback to the user to improve safety and health of the user during activities.

Apple's patent FIG. 1 from that patent, as presented below, illustrates an  Apple Watch; In FIG. 2 the watch (#10) can provide one or more electrodes (#140) for measuring and/or otherwise responding to perspiration. For example, as shown in FIG. 2, the electrodes can be provided on an inner surface of the Apple Watch band (#110).

Apple's patent FIG. 10 above illustrates an exemplary method (#200) for tracking user hydration; FIG. 11 illustrates an exemplary method (#300) for calibrating a hydration tracking system or a watch. You could learn more about that patent report here.

Today the U.S. Patent and Trademark Office officially published a patent application from Apple that extends their work in this feature. The patent relates to systems and methods for determining body water content of a user and more particularly to systems and methods for determining body water content for a user.

Apple's patent background notes that wearable electronic devices like Apple Watch and AirPods are increasingly incorporating sensing systems that measure physiological parameters of a user. In fact, earlier today we covered another patent in a report titled "Apple is working on a new AirPods Health Feature that could assist users detect Heart Pathologies."

In this patent, Apple notes in their patent background that water is a major component of the body and plays an important role in numerous physiological processes. Maintaining body water content is similarly important to a user's health and wellbeing, and a user's body water content may vary with hydration. Recommended body water content may vary between individuals based on a number of factors, such as a user's age, weight, and/or height. However, accurately determining body water content outside of clinical settings can be difficult.

Optical Sensing System For Determining Body Water Content

Apple's latest patent on this project covers embodiments that are directed to an electronic device including a housing, a light emitter, a first detector positioned at a first separation distance from the light emitter, and a second detector positioned at a second separation distance from the light emitter. The wearable device could be an Apple Watch, AirPods or an HMD.

The electronic device can also include a processor that is configured to cause the light emitter to emit light toward a user, receive first measurements from the first detector that represent a first return of the emitted light from the tissue of the user, and receive second measurements from the second detector that represent a second return of the emitted light from the tissue of the user. The processor can determine a decay constant of the emitted light using the first measurements and the second measurements and determine a water content metric of the user using the determined decay constant.

Embodiments are further directed to methods for estimating the body water content of a user. The methods can include emitting light at a first wavelength from one or more light emitters and towards skin of a user, measuring a first return of the emitted light that has interacted with the tissue of a user, the first return of the emitted light associated with a first light emitter and light detector pair having a first separation distance, and measuring a second return of the emitted light that has interacted with the tissue of the user, the second return of the emitted light associated with a second light emitter detector pair having a second separation distance..

To review the full details of this invention, check out patent application 20240315642.