# Development and Calibration of a Microfluidic, Chip-Based Sensor System for Monitoring the Physical Properties of Water Samples in Aquacultures

## TL;DR

A new microfluidic sensor system was developed to measure water temperature and conductivity for aquaculture and environmental monitoring.

## Contribution

A compact, bifunctional chip-based sensor system that measures temperature and conductivity without complex modeling.

## Key findings

- The sensor accurately measures conductivity across a wide range, from river to ocean water.
- Temperature measurements using an on-chip platinum RTD showed no hysteresis effects.
- The system is suitable for inline and online monitoring in aquaculture systems.

## Abstract

In this work, we present a compact, bifunctional chip-based sensor setup that measures the temperature and electrical conductivity of water samples, including specimens from rivers and channels, aquaculture, and the Atlantic Ocean. For conductivity measurements, we utilize the impedance amplitude recorded via interdigitated electrode structures at a single triggering frequency. The results are well in line with data obtained using a calibrated reference instrument. The new setup holds for conductivity values spanning almost two orders of magnitude (river versus ocean water) without the need for equivalent circuit modelling. Temperature measurements were performed in four-point geometry with an on-chip platinum RTD (resistance temperature detector) in the temperature range between 2 °C and 40 °C, showing no hysteresis effects between warming and cooling cycles. Although the meander was not shielded against the liquid, the temperature calibration provided equivalent results to low conductive Milli-Q and highly conductive ocean water. The sensor is therefore suitable for inline and online monitoring purposes in recirculating aquaculture systems.