Small Bioprocess Monitoring Hits the Goldilocks Zone

Source: GEN - Genetic Engineering and Biotechnology News, written by Gail Dutton; research by Yves Mermoud (Eastern Switzerland University of Applied Sciences) (November 4, 2026). AI-generated summary by biochip.com, published November 10, 2026. Not independently reviewed.

Researchers at the Eastern Switzerland University of Applied Sciences and Zurich University of Applied Sciences have built a miniature bioimpedance sensor to track viable cell density in small bioprocesses. The proof-of-concept device has a 1 x 10 mm footprint and works with a 25 µL sample volume. It could help address a monitoring gap as biomanufacturing shifts toward smaller batches, including for more personalized therapies. The team tested the sensor with Chinese hamster ovary cells, a common cell type used to produce biotherapeutics.

A sensor sized for small batches

Process analytical technology, or PAT, uses measurements taken during manufacturing to monitor and control a process. Many existing instruments are built for large-scale production. For small vessels, biocapacitance probes can be too large, while offline cell counts do not provide continuous, real-time readings.

The new device measures electrical impedance, or how a sample responds to an electrical signal. Think of it as sending a small, changing signal through the cell suspension and measuring how the sample responds. The researchers tested signals from 10 kHz to 5 MHz at an amplitude of 200 mV, and reported a detection limit of about 0.5 million cells per milliliter.

How well did it track cell numbers?

The sensor’s readings showed a strong, though imperfect, relationship with reference cell counts. Yves Mermoud, a research scientist at the Eastern Switzerland University of Applied Sciences, reported an R² value of 0.92. In plain terms, a linear relationship accounted for 92% of the variation in the reference measurements.

The researchers fabricated thin-film platinum electrodes on a fused silica wafer using photolithography, a process that patterns features with light. They cut the wafer into 15 x 15 mm microchips, each with two microfluidic channels, and connected the chips to an impedance analyzer. The team reported that deviations at the sensor’s upper and lower measurement limits were comparable to those of commercial probes.

From at-line tests to in-line monitoring

The group has also demonstrated continuous at-line monitoring during 14-day Chinese hamster ovary cell fed-batch cultivations. In those tests, culture circulated through an external module containing the microchip. That setup is different from direct in-line measurement inside a bioreactor.

The researchers are now working to account for changes in the culture medium over time, which can affect the signal. Mermoud says the next steps include packaging the microchip as an insertion probe for direct in-line use and developing multivariate models that combine information from the chip’s sensing modalities.

Why This Matters

Smaller production batches need monitoring tools that fit their scale. A sensor that can measure cell density in a tiny volume could offer bioprocess teams a way to follow cell growth without relying only on samples taken out for offline counting.

The work remains a proof of concept, and direct in-line deployment is still a planned step. The team is seeking industrial partners to support that transition. Whether the device can maintain useful measurements in a wider range of production conditions will be important to establishing its role in small-scale manufacturing.

Start here: Biosensors explained