Chao LIU

• Ph.D.
• Associate Professor at Fudan University

Optical-resolution photoacoustic microscopy (OR-PAM) of oxygen saturation (sO2) offers high-resolution functional information on living tissue. Limited by the availability of high-speed multi-wavelength lasers, most OR-PAM systems use wavelengths around 532nm. Blood has high absorption coefficients in this spectrum, which may cause absorption satur...

We present fast functional optical-resolution photoacoustic microscopy (OR-PAM) that can simultaneously image hemoglobin concentration, blood flow speed, and oxygen saturation with three-pulse excitation. To instantaneously determine the blood flow speed, dual-pulse photoacoustic flowmetry is developed to determine the blood flow speed from photoac...

Micro/nanorobots have long been expected to reach all parts of the human body through blood vessels for medical treatment or surgery. However, in the current stage, it is still challenging to drive a microrobot in viscous media at high speed and difficult to observe the shape and position of a single microrobot once it enters the bloodstream. Here,...

Optical-resolution photoacoustic microscopy (OR-PAM) has been developed for anatomical, functional, and molecular imaging but usually requires multiple scanning for different contrasts. We present five-wavelength OR-PAM for simultaneous imaging of hemoglobin concentration, oxygen saturation, blood flow speed, and lymphatic vessels in single raster...

Functional blood imaging can reflect tissue metabolism and organ viability, which is important for life science and biomedical studies. However, conventional imaging modalities either cannot provide sufficient contrast or cannot support simultaneous multi-functional imaging for hemodynamics. Photoacoustic imaging, as a hybrid imaging modality, can...

Alzheimer's disease (AD), referring to a gradual deterioration in cognitive function, including memory loss and impaired thinking skills, has emerged as a substantial worldwide challenge with profound social and economic implications. As the prevalence of AD continues to rise and the population ages, there is an imperative demand for innovative ima...

Photoacoustic microscopy can image many biological molecules and nano‐agents in vivo via low‐scattering ultrasonic sensing. Insufficient sensitivity is a long‐standing obstacle for imaging low‐absorbing chromophores with less photobleaching or toxicity, reduced perturbation to delicate organs, and more choices of low‐power lasers. Here, the photoac...

Photoacoustic microscopy uses multiple wavelengths to measure concentrations of different absorbers. The speed of sound limits the shortest wavelength switching time to sub-microseconds, which is a bottleneck for high-speed broad-spectrum imaging. Via computational separation of overlapped signals, we can break the sound-speed limit on the waveleng...

Photoacoustic microscopy can image various biological molecules and nano-agents in vivo via low-scattering ultrasonic sensing. Insufficient sensitivity has been a long-standing obstacle for imaging of many low-absorbing chromophores with less photobleaching or toxicity, reduced perturbation to delicate organs, and more choices of lasers. Here, we p...

Viscosity measurement is important in many areas of biomedicine and industry. Traditional viscometers are usually time-consuming and require huge sample volumes. Microfluidic viscometry may overcome the challenge of large sample consumption but suffers from a long process time and a complicated structure design and interaction. Here, we present a p...

Optical-resolution photoacoustic microscopy (OR-PAM) can image blood oxygen saturation (sO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) in vivo with high resolution and excellent sensitivity and offers a great tool for neurovascular study and early cancer diagnosis. OR-PAM ignores the wa...

Microrobots-assisted drug delivery and surgery have been always in the spotlight and are highly anticipated to solve the challenges of cancer in situ treatment. These versatile small biomedical robots are expected to realize direct access to the tumor or disease site for precise treatment, which requires real-time and high-resolution in vivo tracki...

Optical-resolution photoacoustic microscopy (OR-PAM) can image the blood oxygen saturation (sO2) in vivo without labeling. OR-PAM assumes a linear relationship between the photoacoustic amplitude and the optical absorption coefficient and ignores the wavelength-dependent optical fluence attenuation in tissue. However, strong scattering in biologica...

Precise diagnosis and effective treatment of gliomas still remain a huge challenge. Photoacoustic-guided photothermal therapy (PTT) has unique advantages over conventional techniques for brain tumor theranostics, but existing nano-agents for PAI-guided PTT are mainly organic small molecules or inorganic nanoparticles, which have the limitations of...

Hydrogen sulfide (H2S) has been recognized to influence a wide range of physiological and pathological processes. Its underlying molecular events, however, are still poorly understood. An activatable H2S probe for photoacoustic (PA) imaging is desirable to further explore the role of H2S in vivo. Nevertheless, only a few activatable PA probes for H...

Dichroism is a material property that causes anisotropic light-matter interactions for different optical polarizations. Dichroism relates to molecular types and material morphology and thus can be used to distinguish different dichroic tissues. In this paper, we present single-shot dichroism photoacoustic microscopy that can image tissue structure,...

Flexible and stretchable electronics have attracted great attentions and been widely used in wearable devices and electronic skins, where the circuits for flexible and stretchable electronics are typically in plane based 2D geometries. Here, we introduce a 3D microprinting technology that can expand one more dimension of the circuit in flexible ele...

Microrobots capable of performing targeted delivery are promising for biomedical applications. Due to the restriction of their small size and volume, however, the real-time in vivo imaging strategy for microrobots meets limitations at the current stage. Performing swarm actuation and control may be a promising candidate to increase the contrast o...

Photoacoustic (PA) imaging and tracking of stem cells plays an important role in the real-time assessment of cell-based therapies. Nevertheless, the limitations of conventional inorganic PA contrast agents and the narrow range of the excitation wavelength in the first near-infrared (NIR-I) window hamper the applications of PA imaging in living subj...

We present the development of single-cell photoacoustic microscopy. A multi-wavelength laser source is developed with 2-MHz pulse repetition rate, 220-ns wavelength switch time, and hundreds of nano-Joules pulse energy. We demonstrate in vivo photoacoustic imaging of single red blood cells.