Miniaturized multi-sensor for aquatic studies

Abstract

We have developed and fabricated a multi-sensor chip for fisheries’ research and demonstrated the functionality under controlled conditions. The outer dimensions of the sensor chip are 3.0 × 7.4 × 0.8 mm3 and both sides of the chip are utilized for sensors. Hereby a more compact chip is achieved that allows for direct exposure to the seawater and thereby more accurate measurements. The chip contains a piezo-resistive pressure sensor, a pn-junction photodiode sensitive to visible light, a four-terminal platinum resistor for temperature measurement and four conductivity electrodes for the determination of the salinity of saltwater. Pressure, light intensity, temperature and salinity are all essential parameters when mapping the migration route of fish. The pressure sensor has a sensitivity of S = 1.44 × 10−7 Pa−1 and is optimized to 20 bar pressure; the light sensor has a quantum efficiency between 52% and 74% in the range of visible light. The temperature sensor responds linearly with temperature and has a temperature coefficient of resistance of 2.9 × 10−3 K−1. The conductivity sensor can measure the salinity with an accuracy of ±0.1 psu. This is all together the smallest and best functioning fully integrated MEMS-based multi-sensor made to date for this specific application. However, each single-sensor performance can be optimized by introducing a considerably more complicated process sequence. In this paper, a new simpler process for integrating the four sensors on one single chip is presented in details for the first time. Further, an optimized performance of the individual sensors is presented.

MEMS-Based Micro Sensors for Measuring the Tiny Forces Acting on Insects

“…However, several MEMS force sensors have been developed for swimming animals. In biologging research, pressure and flow sensors utilizing MEMS technology have been developed to measure the swimming depth and waterflow velocity by attaching several sensor units to the bodies of marine animals [ 131 , 132 ]. Meanwhile, swimming animals have sensory organs on their body surfaces that detect hydrodynamic forces, which inspired the development of several MEMS force sensors [ 133 , 134 ].…”

Cost-Efficient Oceanographic Instrument with Microfabricated Sensors for Measuring Conductivity, Temperature and Depth of Seawater

“…The development of low-cost instrumentation plays a key role in marine environmental studies and represents one of the most innovative aspects of current oceanographic research [ 5 ]. Recent developments of CTD instruments with a small size and low power consumption, suitable for mounting on gliders or AUVs and attaching to marine animals, have been reported in [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. For near-shore oceanographic research on the continental shelf, where the water depth rarely exceeds 200 m, the cost expense of CTD research is a barrier for formal and informal researchers working with limited budgets, including scientists from developing nations, citizen oceanographers, environmental educators, and students of all levels interested in understanding their local coasts and waterways.…”

Towards Chip-Based Salinity Measurements for Small Submersibles and Biologgers

“…An even more recent publication by the same authors [22] reports an uncertainty of ±0.1 PSU for a different version of the sensor chip, being 3.0 × 7.4 × 0.8 mm 3 in size, probably due to a larger electrode area. The sensitivity of the pressure sensor was now reported to be 1.44 × 10 −3 dbar −1 .…”