What Do Different Modes of AFM-IR Mean for Measuring Soft Matter Surfaces?

In the past decade, rapidly emerging atomic force microscopy-based photothermal infrared microscopy (AFM-IR) techniques have routinely delivered surface chemical imaging with tens of nanometers spatial resolution. The commercial availability of AFM-IR instruments has accelerated their popularity among soft matter and surface science communities. Various AFM-IR modes exist with different characteristics. In this Perspective, we discuss the challenges and opportunities associated with many AFM-IR modes, clarifying the possible confusion arising from terminologies and describing the possible benefits of using multiple AFM-IR modes for a better understanding of the nanoscale composition organization of the interface.