ANTIGONE: A Programmable Energy-Efficient Current Digitizer for an ISFET Wearable Sweat Sensing System

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Wearable Technology

Background:

• Continuous health monitoring is crucial for personalized and preventive healthcare.
• Existing biosensing systems often lack the sensitivity and efficiency for real-time sweat analysis.
• Ion-Sensitive Field-Effect Transistors (ISFETs) offer potential for noninvasive biomarker detection.

Purpose of the Study:

• To design and characterize ANTIGONE, an energy-efficient Application Specific Integrated Circuit (ASIC) for low DC-current sensing.
• To enable real-time, noninvasive health monitoring through the detection of biomarkers in human sweat.
• To develop a system capable of interfacing with multiple ISFETs for multiplexed biomarker analysis.

Main Methods:

• Designed the ANTIGONE ASIC using AMS 0.35 μm technology, employing a current-to-frequency converter architecture based on charge balancing.
• Implemented a time-multiplexing front-end capable of digitizing currents from four sweat ISFET sensors.
• Integrated a Serial Peripheral Interface (SPI) for control and data readout, with Bluetooth Low Energy (BLE) communication via an MCU for portable device integration.

Main Results:

• The ANTIGONE ASIC demonstrates good linearity over a wide dynamic range (1 pA to 500 nA).
• Achieved low energy consumption per conversion (less than 1 μJ), enhancing energy efficiency.
• The chip is programmable with eight operating modes and supports multiplexed sensing of multiple biomarkers (pH, Na+, K+, Ca2+).

Conclusions:

• The ANTIGONE ASIC provides an efficient solution for low DC-current sensing in wearable health monitoring systems.
• The developed ISFET-ASIC system facilitates real-time, noninvasive, and continuous monitoring of key health biomarkers in sweat.
• This technology contributes to a broader wearable platform for personalized and preventive healthcare by integrating multiparameter biosensors.