Apparatus and methods for monitoring concentrations of analytes in body fluid

A remote concentration monitor system comprising:

• an untethered battery-free remote concentration monitor comprising one or more pairs of anode and cathode electrodes attached on a surface of the remote concentration monitor and configured to generate a current when contacting a gastric acid of a subject, a capacitor configured to be charged by the generated current, an encapsulated circuit configured to be powered by energy harvested from the gastric acid through the one or more pairs of anode and cathode electrodes, wherein the remote concentration monitor is configured to be temporarily fixed in an esophagus wall of the subject by endoscopic administration;
• and
• a waterproof external data recorder configured to receive radio frequency pulse signals generated by using the gastric acid to charge the capacitor that discharges upon reaching a voltage threshold, wherein a frequency of these pulse signals is determined by a charging rate of the capacitor, which varies according to a concentration of the gastric acid, wherein a decoded frequency of the pulse signals embodies the concentration of the gastric acid;
• wherein the waterproof external data recorder further comprises a signal receiver, a micro controller, a data storage medium, and a screen,
• wherein the untethered battery-free remote concentration monitor is configured to be inside a body of the subject,
• wherein the micro controller is configured to be in sleep mode when no gastric acid is detected in an esophagus of the subject,
• wherein the remote concentration monitor is configured to be powered by energy harvested from the gastric acid in the esophagus of the subject at pH values ranging from 1 to 4,
• wherein the micro controller is configured to wake up and transmit pulse signals when the charging rate of the capacitor reaches the voltage threshold, and
• wherein the current generated by the one or more pairs of anode and cathode electrodes is positively proportional to the concentration of the gastric acid, wherein the waterproof external data recorder is configured to receive data from inside the body of the subject, to record the concentration of the gastric acid in the data storage medium, and to display real-time gastric acid concentration and GERD severity on the screen, wherein the waterproof external data recorder is configured to be portable.