(a,b) Comparison of mid-IR absorption spectrum of selected biomolecules measured by standard ATR-FTIR spectroscopy (blue lines) and MiROM (red lines). (a) DNA and (b) albumin in D2O. The vertical dashed lines indicate a good matching of the main absorption bands measured by standard ATR-FTIR and mid-IR optoacoustic spectroscopy. A detailed comparison of the position of the measured absorption bands for each biomolecule is shown in Supplementary Tables 2–5. (c-e) MiROM imaging/spectroscopy of water. (c) Micrograph of water and carbon tape at 1650 cm−1. Arrow 1 indicates where the optoacoustic signal of water was recorded while arrow 2 indicates where the reference signal was measured from the carbon tape, scale bar: 200 μm. (d) MiROM spectrum of water. The dashed line indicates the wavelength (1650 cm-1) used to obtain the image in c. (e) Intensity profile at the white-dashed line in c showing the contrast level in water, carbon tape, and voids in the carbon tape. Data in a-e are representative of three independent experiments.