How to use stimuli-responsive soft materials for detection?

The growing demand for rapid, cost-effective, and user-friendly detection methods has driven advancements in “stimuli-responsive soft materials” for sensor development. Many examples of complex and liquid crystals emulsions can be found demonstrating their application for the detection of bacteria, virus, enzyme, or specific molecules. However, despite frequent comparisons between emulsions and foams, the exploration of liquid foams for sensor applications remains limited. Paradoxically, foam-based sensors for fetal lung maturity were developed in the 1970s, before the emergence of more sophisticated detection methods. Here, we describe some examples of soft interfaces used as sensor to detect biomarkers, enzymes, and bacteria, with a strong emphasis on foam. We demonstrate how to use the foamability and foam stability as read-out mechanism. We discuss approaches developed for complex emulsions and liquid crystals, highlighting their potential adaptation to liquid foams. • Foams are molecular magnifying glasses: events at the nanoscale level are observed by naked eye. • For detection, drastic changes in foamability or foam stability can be designed. • We describe the examples of liquid foam sensors in the literature. • Complex and liquid crystals emulsions are also used for detection. • Possible links exist between emulsions and liquid foam for sensing.