Abstract
Ultrasound detectors use high-frequency sound waves to image objects and measure distances, but the resolution of these readings is limited by the physical dimensions of the detecting element. Point-like broadband ultrasound detection can greatly increase the resolution of ultrasonography and optoacoustic (photoacoustic) imaging1,2, but current ultrasound detectors, such as those used for medical imaging, cannot be miniaturized sufficiently. Piezoelectric transducers lose sensitivity quadratically with size reduction3, and optical microring resonators4 and Fabry-Pérot etalons5 cannot adequately confine light to dimensions smaller than about 50 micrometres. Micromachining methods have been used to generate arrays of capacitive6 and piezoelectric7 transducers, but with bandwidths of only a few megahertz and dimensions exceeding 70 micrometres. Here we use the widely available silicon-on-insulator technology to develop a miniaturized ultrasound detector, with a sensing area of only 220 nanometres by 500 nanometres. The silicon-on-insulator-based optical resonator design provides per-area sensitivity that is 1,000 times higher than that of microring resonators and 100,000,000 times better than that of piezoelectric detectors. Our design also enables an ultrawide detection bandwidth, reaching 230 megahertz at -6 decibels. In addition to making the detectors suitable for manufacture in very dense arrays, we show that the submicrometre sensing area enables super-resolution detection and imaging performance. We demonstrate imaging of features 50 times smaller than the wavelength of ultrasound detected. Our detector enables ultra-miniaturization of ultrasound readings, enabling ultrasound imaging at a resolution comparable to that achieved with optical microscopy, and potentially enabling the development of very dense ultrasound arrays on a silicon chip.
🔬 Techniques
🔭 Microscopes
✨ Fluorophores
🧪 Sample Preparation
🔬 Cell Lines
🧪 Reagent Suppliers
📷 Detectors
🏛️ Research Organizations (ROR)
Affiliated research institutions:
📊 Figures
Figure 1
Principles of photoacoustic tomography (PAT)
(a) Jablonski diagram, illustrating the photon energy transfer in one-photon fluorescence microscopy, two-photon fluorescence microscopy, and PAT. The most common electronic absorption in the visible ...
Figure 2
Representative implementations of PAT
(a) Transmission-mode OR-PAM system, where the ultrasonic transducer (UT) and the water-immersion focusing lens are on opposite sides of the object 98 . Note that the focusing lens has a numerical ape...
Figure 3
Practical guide to mapping the desired imaging depth, speed and contrast to the optimal PAT implementation
For a specific biological problem, the most suitable category of PAT implementations depends primarily on the desired imaging depth. The representative reference for each PAT implementation is indicat...
Figure 4
Photon propagation regimes in soft tissue and the penetration limits of representative high-resolution optical imaging modalities
(a) Photon propagation regimes in soft tissue and association with the penetration limits of high-resolution optical imaging modalities 34 . The four regimes are divided approximately at photon propag...
Figure 5
Multiscale PAT of single cells, whole-body small animals, and humans
(a) PAT implementations with approximate spatial resolutions and penetration limits suitable for structures ranging from organelles to whole-body small animals and humans. SR-PAM, super-resolution PAM...
Figure 6
In vivo PA molecular imaging
(a) PA images acquired at multiple wavelengths are combined with spectral unmixing algorithms to separate different types of optical absorbers 101 . This example shows an NIR organic dye (shown in gre...
Figure 7
Representative in vivo PAT applications in life sciences
(a) Whole-cortex OR-PAM image of the oxygen saturation of hemoglobin in a mouse brain 53 . The arteries (shown in red) and veins (shown in green) are clearly differentiated by their oxygenation levels...
Figure images are served from the NIH/NLM PubMed Central Open Access Subset or Europe PMC; copyright remains with the publishers and authors.
💬 Discussion
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