Ion Sensitive Field-Effect Transistor (ISFET)

An image of a component layout on MEMS pH meter based on custom ISFET made by LioniX International.

MEMS pH sensor based on custom ISFET.

LioniX International is an OEM supplier of bare Ion Sensitive Field-Effect Transistor (ISFET) chips.

With our bare ISFET dies as a foundation, the possibilities for sensor development are vast. Whether you’re aiming to create a pH sensor or an ion sensor, our ISFET process provides a solid framework. While the process itself remains fixed, the design could be customized to meet the requirements posed by your probe design or any packaging constraints you may encounter.

Our ISFET chips are characterized by high sensitivity, low drift, and low light sensitivity. Our standard production process is based on ion implantation, gate oxidation, diffusion, and a tantalum oxide ( Ta2O5) gate dielectric.

This configuration offers superb performance compared to ISFET with aluminum oxide (Al2O3) or silicon nitride (Si3N4) gates. The device is customizable and uncalibrated, allowing for full access to a sensor, that could be quipped with a protection electrode for electro static discharge (ESD).

We fabricated miniature ISFET chips with backside contacts to be used in a guidewire tip inserted into the brain vasculature of patients suffering from stroke.

Looking for off-the-shelf ISFET solutions?

A picture of a packaged ISFET ready for evaluation

A picture of a packaged ISFET.

We are partnering on this with Microsens! We are producing the chips, they create the pH sensor. Microsens provide an evaluation kit which contains some packaged ISFET probes, a miniature reference electrode and readout/drive electronics. It is plug-and-play and therefore requires no further development from your side.

For small volumes and/or evaluation of the ISFET for customer-specific use cases it is recommended to evaluate the Microsens evaluation kit before developing your own application based on our OEM chips.

Take a look at Microsens evaluation kit here.


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.

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.

No, we only supply the bare ISFET chips.

Minimum quantity of the bare ISFET chips is 1 wafer, which equals approximately 100 – 2000 chips, depending on the design, which is customizable.

🌐Learn more about MEMS Technology development at LioniX International.