Optoacoustic (OA) methods have become powerful tools in biomedical research capable of retrieving functional information from biological tissues in vivo. Acquisition of OA signals generally relies on direct physical contact of a transducer or an acoustic coupling medium with the tissue surface, which prevents applicability, e.g., in open surgeries or wounded tissues. Non-contact OA imaging has been achieved with air-coupled piezoelectric transducers, which provide a straightforward approach for remote sensing of ultrasound vibrations. However, sensitivity was hampered by a suboptimal alignment between the illumination and detection fields. Herein, we devised an air-coupled transducer featuring a central aperture for light delivery with coaxially aligned optical and acoustic foci, thus providing optimal sensitivity for OA signal detection. Imaging of phantoms and a mouse ear in vivo is showcased by raster-scanning the transducer with light being delivered through a multimode optical fiber.
This work was supported by the Helmut Horten Stiftung (X.L.D.B.; Project Deep Skin), the National Natural Science Foundation of China (J.L.; Grant Nos. 81771880 and 82171989), the Tianjin Municipal Government of China (J.L.; Grant No. 19JCQNJC12800), the Spanish Universities Ministery (F.M.d.E.; Salvador de Madariaga grant), and the European Research Council (D.R.; Grant No. ERC-2015-CoG-682379).