Planar Microfabricated Water Sensor with Bare Electrodes
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Solution Overview
Problem
Existing sensors for measuring conductivity, temperature, and dissolved oxygen in water face challenges such as high power consumption, fragility, complex manufacturing processes, slow response times, biofouling, and high costs, which limit their accuracy and long-term performance, especially in miniaturized and cost-effective applications.
Innovation Solution
The development of an apparatus with a substrate-based conductivity and temperature sensor system featuring bare electrodes, strain compensation, and an open cell design for reduced proximity effects, combined with a dissolved oxygen sensor using bare metal electrodes without oxygen-permeable membranes, and integrated electrochemical generation of chlorine for antifouling, all fabricated using planar microfabrication techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional conductivity, temperature, and dissolved oxygen sensors are used, then measurement accuracy is achieved, but device size and power consumption increase
Solution Approach 1:
The patent combines multiple sensing functions (conductivity, temperature, dissolved oxygen) into a single integrated sensor device with a unified substrate and common electrode structure. This merging eliminates the need for separate sensor housings, power supplies, and processing units that would individually consume power, while maintaining high measurement accuracy for all three parameters through shared signal processing circuitry.
Solution Approach 2:
The sensor device performs multiple measurement functions simultaneously using a single device architecture. The conductivity sensor, temperature sensor, and dissolved oxygen sensor all operate from one integrated platform, allowing the device to provide comprehensive water quality monitoring without requiring multiple separate instruments, thereby reducing overall power consumption while maintaining individual measurement accuracies.
2Reliability
If membrane-covered electrodes are used to prevent biofouling, then sensor durability improves, but response time and sensitivity decrease
Solution Approach 1:
The sensor employs electrochemically generated chlorine from chloride ions in the water to actively clean its own surfaces. By applying a cleaning potential to the electrodes, the system generates hypochlorous acid and other reactive species that oxidize and remove organic fouling deposits in real-time, allowing the sensor to maintain its response characteristics without physical membranes or external cleaning mechanisms.
Solution Approach 2:
The system dynamically changes the electrical potential parameter applied to the electrodes between measurement mode and cleaning mode. During measurement, a low potential maintains sensing accuracy; during cleaning intervals, a higher potential generates chlorine for biofouling removal. This parameter switching allows the same electrode surface to provide both durable operation and fast response times without requiring protective membranes.
3Volume of moving object
If complex microfabrication processes are used to制造 miniaturized sensors, then device size reduces, but manufacturing complexity and cost increase
Solution Approach 1:
The sensor utilizes uniform planar electrode patterns fabricated using standard photolithography techniques on a flat substrate. All electrodes (conductivity, temperature, dissolved oxygen) follow similar geometric designs and fabrication steps, avoiding complex three-dimensional structures, precision dicing, or specialized deposition processes. This homogeneous approach enables mass production with conventional semiconductor manufacturing equipment, reducing both complexity and cost while achieving miniaturization.
4Measurement precision
If precision dicing and multi-step deposition are used for MEMS sensor fabrication, then sensor performance improves, but automation for mass production becomes difficult
Solution Approach 1:
The patent extracts the sensing functions from complex MEMS structures and implements them using simple planar electrode geometries on a flat substrate. By removing the need for precision dicing, three-dimensional etching, and multiple deposition layers, the design allows all sensors to be fabricated in a single photolithography step on large wafers, which can then be automatically diced into individual devices using standard automation equipment, greatly improving mass production capability while maintaining adequate sensor performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables high-accuracy, miniaturized, and cost-effective sensing of conductivity, temperature, and dissolved oxygen with improved response times, reduced biofouling, and increased stability, suitable for various water applications including oceanography and freshwater monitoring.
Implementation Method 1
a conductivity sensor for sensing conductivity in water; the conductivity sensor is an electrode-based conductivity sensor
Implementation Method 2
a temperature sensor for sensing the temperature of the water; the temperature sensor comprises electrically resistive paths
Implementation Method 3
a dissolved oxygen sensor for sensing dissolved oxygen in water
Implementation Method 4
integrated electrochemical generation of chlorine for antifouling
Data Source
AI summary
Apparatus (2) for sensing at least one parameter in water, which apparatus (2) comprises: (i) a conductivity sensor (6) for sensing conductivity in water; (ii) the conductivity sensor (6) is an electrode-based conductivity sensor having bare electrodes (12) which contact the water; (iii) there are at least four of the electrodes (12); (iv) the conductivity sensor (6) is fabricated on a substrate (14) using photolithography and etching; (v) the conductivity sensor (6) is an open cell sensor having a physically unconstrained electric field; (vi) the conductivity sensor (6) is of a dot construction comprising a dot and a surrounding formation; (vii) the conductivity sensor (6) has two electrodes which are for current stimulation and which geometrically bound and enclose another two electrodes which are for voltage sensing; and (viii) the conductivity sensor (6) is a laminar construction on the substrate (14).