A Wirelessly-Enabled, Power-Optimized, Low-Cost, and Open-Source Durafet-based pH Instrument for Continuous, Long Term Environmental Monitoring

The increasing acidity of our oceans, exacerbated by human activities, represents a growing threat to the human societies that rely upon healthy marine ecosystems. Research activities to collect data on the progression of ocean acidification are a crucial part of efforts to monitor, assess, and mitigate impacts. However, high-cost, commercially available monitoring tools represent a major barrier to comprehensive data collection and community engagement, especially for ocean acidification research. Here, we present an iteration to our open-source, low-cost pH sensor design which utilizes a Durafet pH electrode. We developed significant improvements to optimize energy consumption, simplify assembly, and add wireless functionality while maintaining affordability. We performed low-power hardware and firmware modifications which extend the battery lifespan. We designed a custom PCB that reduces assembly error, improves modularity, and maintains a compact footprint. Finally, we implemented bi-directional wireless functionality in our design, enabling wireless data retrieval and sensor re-programming, a feature that is notably absent in commercially available counterparts. With the addition of these features, we have designed open-source pH sensor electronics that are more affordable and accessible while maintaining high performance. Expanding sensor networks benefits everyone, by equipping researchers, policymakers, and communities with the knowledge and resources required to understand and adapt to our rapidly changing world.