# Dual‐function, Reusable, and Flexible Thermal Interface for Kinetic Monitoring of In Vitro Bioassays

## TL;DR

A new thermal interface allows non-contact monitoring of biological processes and temperature control, showing better sensitivity than optical methods in certain cases.

## Contribution

A reusable, dual-function thermal interface for microwell-independent temperature control and sensing in bioassays is introduced.

## Key findings

- The thermal interface showed increased response signal compared to optical density measurements in interface-dominated processes.
- An autonomous data analysis approach for mTPS data was developed, offering robustness and lower susceptibility to errors.
- The interface is reusable, low-cost, and non-contact, making it suitable for dynamic biological studies.

## Abstract

Kinetic monitoring in life sciences is predominantly performed using contactless optical techniques. Miniaturized electronic sensing alternatives typically require direct contact with the sample. We introduce a dual‐function thermal actuator/sensor that uniquely combines microwell‐independent temperature control of a modified microplate and simultaneous measurement of real‐time changes in thermal effusivity, offering both electronic readout and contactless sensing. The performance is demonstrated by monitoring Escherichia coli (E. coli) growth and assessing the effect of cefotaxime (CTX) as a use‐case application, benchmarking it against state‐of‐the‐art optical techniques. By qualitative comparison of characteristic data features, we report that the thermal sensing modality showed an increased response signal compared to optical density (OD) measurements in interface‐dominated processes, which can be observed under experimental conditions where metabolic or morphological adaptation happens in response to CTX. Additionally, we developed an autonomous full curve data analysis approach for modified Transient Plane Source (mTPS) data, offering high robustness and lower susceptibility to systematic errors and bias. Our technique emphasizes interface‐dominant processes, thereby complementing the assessment of bulk properties obtained by traditional optical techniques. The developed thermal interface is reusable, highly integrable, low‐cost, easy to use, non‐contact, and label‐free, offering a versatile platform for bioassay development and dynamic biological studies.

This work presents a reusable, dual‐function thermal interface for non‐contact, label‐free sensing and microwell‐independent temperature control in microplates within a single element. Real‐time monitoring of E. coli growth and the response to antibiotic treatment demonstrates the sensor's enhanced sensitivity in interface‐dominated processes compared to optical techniques. This method provides a powerful complement to the kinetic monitoring landscape in life sciences.