OpenMux Overview

OpenMux is an extension of the research conducted within the framework of the OPTIRAS project, particularly from the Water Quality Group at the International Iberian Nanotechnology Laboratory. We aim to provide an open-source multiplexer adaptor for the EmStat4 LR/HR potentiostat by combining hardware design with software integration. This innovation enhances experimental efficiency and scalability for researchers and engineers at an exceptionally low cost, paving the way for applications such as multiplexed electrochemical sensing, automated assay platforms, and integrated IoT-based field monitoring systems for environmental, biomedical, or industrial electrochemical analysis.

The use of OpenMux is demonstrated in the article "Multiplexed potentiometric sensing of nitrite in environmental waters" [1].

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About

This repository provides OpenMux, a homemade and cost-effective multiplexer adaptor for the EmStat4 OEM module from Palmsens. The adaptor is integrated with the potentiostat using the MethodScript protocol provided by the manufacturer.

The system consists of two main modules:

1. Hardware Module – the multiplexer adaptor (figure 1), whose schematics and PCB layout were developed using KiCad 7.0. Schematic, layout, and Gerber files can be found in the Hardware/ folder (see schematic.pdf and layout.pdf for pictures).
2. Graphical User Interface (GUI) – a graphical user interface (figure 2) to control the adaptor, implemented in Python 3.8. The GUI is located in the Application/ folder.

Figure 1: OpenMux adaptor for EmStat4

Figure 2: OpenMux GUI

The application of OpenMux for electrochemical methods is described in the scientific literature [2].

Who is this for?

• Electrochemists who want a cheap and modular, open platform for integrating sensors and data backends for:
  • Environmental or industrial monitoring applications
  • Scaling up sensor optimisation and/or preparation in the lab

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Costs

The approximate cost of the electronic components (excluding the PCB) is around €40. Key components include:

Quantity	Component	Price	Link
3x	ADG1408YRUZ Multiplexer	€10	Digi-Key
3x	Phoenix Terminal Block 8-pos	€1.60	Digi-Key
3x	Male Pin Header 12-pos	€0.14	Digi-Key
3x	Female Pin Header 12-pos	€0.49	Digi-Key

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Getting Started

1. Clone or download the repository

git clone https://github.com/WaterQuality-INL/OpenMux.git
cd OpenMux

2. Hardware and production

• Gerber files for production: Hardware/production/Mux_Module.zip
• Schematics and PCB: in Hardware/ (KiCad 7.x)
• Fabricate the PCB (JLCPCB, PCBWay, etc.), order components, and assemble.

3. Software requirements

• Python 3.8 or newer (3.8–3.11 recommended)
• OS: Windows, Linux, or macOS (GUI tested on Windows; Linux/macOS supported)
• The Application uses MethodScript-firmware/ and Icons/ folders; these must be present when running the packaged executable (see Packaging below).

4. Run the GUI (development)

Windows (cmd / PowerShell)

cd Application
python -m venv venv
venv\Scripts\activate.bat    # PowerShell: venv\Scripts\Activate.ps1
pip install -r requirements.txt
python EL_MUX.py

Linux / macOS

cd Application
python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt
python3 EL_MUX.py

5. OPTIONAL: Packaging (creating an executable)

Alternatively, an executable file can also be created, allowing this application to run in computers where python is not installed.

cd Application
venv\Scripts\activate.bat
pyinstaller -w -p "venv\Lib\site-packages" -i Icons/group-30_116053.ico --onefile EL_MUX.py

Notes:

• The produced executable still depends on the folders MethodScript-firmware/ and Icons/. Place EL_MUX.exe into Application/ alongside those folders before running.
• After verifying the executable works, you can remove the build/ and dist/ directories.

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Troubleshooting

• If the GUI cannot find the EmStat4 device, verify the USB/serial connection and port name.
• Ensure the virtual environment is activated and dependencies installed.
• For packaging issues, build the executable on the target OS (pyinstaller builds are OS-specific).

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License

• Software (Application/) is licensed under the MIT License.

• Hardware (Hardware/) is licensed under CC BY 4.0

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Contributors

• Samuel Silva*

Supervision:

• Álvaro Geraldes**

Contacts:

• Samuel Silva, samuel.silva@inl.int
• Álvaro Geraldes, alvaro.geraldes@inl.int

*Water Quality Group, **Systems Engineering Group, International Iberian Nanotechnology Laboratory (INL)

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Acknowledgement

To PalmSens for MethodScript

This work is an extension of the research project funded by EEA (European Economic Area) Grants Portugal through the funded project PT-INN-0076—OPTIRAS.

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References

[1] Renato L. Gil, Samuel Silva, Marília B. Santos, Álvaro Geraldes, Begoña Espiña, Raquel B. Queirós. Multiplexed potentiometric sensing of nitrite in environmental waters. Analytica Chimica Acta 2026, https://doi.org/10.1016/j.aca.2026.345190

[2] Olesia Dudik, Renato L. Gil, Raquel B. Queirós. Critical assessment of different ion-to-electron transducers in modified screen-printed electrodes for potentiometric lithium sensing. Microchemical Journal 2025, 215, 114195, https://doi.org/10.1016/j.microc.2025.114195