Cover Feature: Synthetic Thermo-Sensitive Hydrogel Microspheres as Temperature Probes in an Optical Tweezers Setup (Chem. Methods 7/2025)

The Cover Feature shows poly-N-isopropyl-acrylamide (PNIPAAm) microspheres on a glass slide in water. PNIPAAm is a temperature-sensitive polymer that undergoes a volume transition between 20 and 45 °C. The spheres were fluorescently labelled and imaged with confocal fluorescence microscopy at 22 °C (top left) and at 45 °C (bottom right). In their Research Article (DOI: 10.1002/cmtd.202400040), R. Sorkin, A. Lesman and co-workers explain how they used the volume transition of PNIPAAm microspheres to measure the temperature close to a powerful optical tweezers laser beam. Measuring the temperature directly by using PNIPAAm helps to conduct optical tweezers experiments, especially with biological samples, and provides an additional control variable.