System for determining fluid level in a biological subject

A system for performing fluid level measurements on a biological subject, the system including:

• a) at least one substrate including a plurality of microstructures configured to breach a stratum corneum of the biological subject, at least some microstructures including an electrode and wherein the microstructures are conductive and include an insulating layer extending over an end of the microstructure proximate the substrate so that at least a tip portion of the microstructure is uncoated and acts as the electrode, and wherein at least some of the microstructures include a shoulder that is configured to abut against the stratum corneum to control a depth of penetration;
• b) a signal generator operatively connected to at least one microstructure pair to apply an electrical stimulatory signal between microstructures in the at least one microstructure pair, wherein microstructures in the at least one microstructure pair each have respective electrodes in opposition from one microstructure and another microstructure, and wherein the electrical stimulatory signal generates an electric field between the respective electrodes;
• c) at least one sensor operatively connected to the at least one microstructure pair, the at least one sensor being configured to measure electrical response signals between microstructures in the pair;
• and,
• d) one or more electronic processing devices that are configured to:
• i) determine measured electrical response signals, the response signals being at least partially indicative of a bioimpedance;
• and,
• ii) perform an analysis at least in part using the measured electrical response signals to determine at least one indicator at least partially indicative of fluid levels in the subject and wherein the system is configured to perform repeated measurements over a time period so that changes in impedance are used to track changes in fluid levels over time.