MBARI – ISFET for deep sea pH sensor
LioniX is an OEM supplier of bare Ion Sensitive Field-Effect Transistor (ISFET) chips.
Application
Our ISFET chips enabled the Monterey Bay Aquarium Research Institute (MBARI) to develop a pH sensor device designed for precise and stable deep-sea measurements. It ensures accurate analysis of deep-water pH over long (years) time periods. The pH sensor is a core component of a robotic platform that tracks properties, including oxygen levels, pH, nutrients, and chlorophyll, at any location and time. Performance evaluations demonstrated that the sensor has remarkable stability, high responsiveness, and exceptional temperature sensitivity.
The chemical sensors team at MBARI works to gain insight in actual trends of such fundamental properties to better understand our changing ocean. Their work is made increasingly relevant by the rapidly evolving conditions of our biosphere.
MBARI “SURpH” pH sensor (Semiconductor UnderwateR pH) built around Lionix ISFET chip.
Request
MBARI approached us with a new challenge: they needed bare ISFET dies (Ion Sensitive Field effect transistors) to replace the previous chips that were no longer in production. MBARI required a custom design tailored to their packaging and assembly go to options, which are adapted for the deep-sea usage.
We leveraged our flexibility to develop a solution accommodating our client specific requirements for such a highly demanding environment.
Solution
LioniX customized their standard ISFET design and produced ISFET dies, around which MBARI built a pressure tolerant pH sensor for deep sea applications.
According to MBARI, the sensor’s performance is excellent: stable over time, with high responsiveness and improved pressure balancing.
LioniX ISFET properties
- Ta2O5 gate (tantalum pentoxide)
- Nearly exact Nernstian response, 58 mV / pH at RT
- FET type: n-channel
- Fixed process, customizable design
- Delivered as naked dies on foil
- Up to 2000 ISFETs per wafer
ISFET DEVELOPMENT AT LIONIX INTERNATIONAL
Our ISFET chips are characterized by high sensitivity, low drift, and low light sensitivity, based on ion implantation, gate oxidation, diffusion, and a tantalum oxide (Ta2O5) gate material.
The device is customizable and uncalibrated, allowing for full access to the sensor.
What is an ISFET?
The Ion Sensitive Field Effect Transistor (ISFET) is a solid state, potentiometric sensor capable of measuring pH in the range of pH 1 to pH 14 with a linear response.
How to turn bare ISFET into pH sensors?
To turn bare ISFET dies into working pH sensor systems, you need to add the following yourself:
- Packaging of the chip (mounting on a substrate or in a probe, electrical contracting and sealing the chip exposing only the ISFET gate to the liquid)
- External Reference Electrode
- Readout and control electronics
Bare ISFET chips are usually interesting for larger volumes and customers that have the above expertise and are willing to bear the associated development costs. This development requires in-depth knowledge about the ISFET principles.
Does LioniX supply pH sensors?
No, we only supply the bare ISFET chips.
What is the minimum order quantity?
Minimum quantity of the bare ISFET chips is 1 wafer, which equals approximately 100 – 2000 chips, depending on the design, which is customizable