This paper reports the modelling and experimental results of a liquid-core liquid-cladding optofluidic lens. The lens is based on three laminar streams in a circular chamber. The stream lines and the curvature of the interface can be predicted accurately using the theory of two-dimensional dipole flow in a circularly bounded domain. The model establishes basic relations between the flow rate ratio of the core/cladding streams and the radius of curvature and consequently the focal length of the lens. Compared to a rectangular chamber, this new circular design allows the formation of a liquid-core liquid-cladding lens with perfect curvatures. The circular design allows tuning a perfect curvature ranging from the chamber radius itself to infinity. The test device with a circular lens chamber with 1 mm diameter and 50 microm height was fabricated in PDMS. The lens shape as well as the stream lines were characterized using fluorescent dye and tracing particles. Experimental results agree well with the analytical results predicted by the model.

In this Letter, we present a high-resolution photoacoustic endomicroscopy probe based on a microelectromechanical systems (MEMS) scanning mirror. The built-in optical assembly consists of a 0.7 mm graded-index (GRIN) lens for light focusing and a ϕ1  mm MEMS mirror to reflect and scan the beam. A miniaturized unfocused ultrasound transducer with a center frequency of 10 MHz is used for photoacoustic detection. Sharp blades, carbon fibers, and black tapes were utilized to evaluate the performance of the system. In vivo mouse ears and resected rectums were imaged to further demonstrate the feasibility of this probe for potential biological and clinical applications.

Recently, intensive research has been conducted to accelerate the development of photoacoustic (PA) imaging modality for biomedical applications. The use of acoustic lenses to collect ultrasound signals is of great interest. This Letter presents the design and fabrication of a liquid acoustic diverging lens, which can enlarge the acceptance angle of an ultrasound transducer. This lens possesses an inherent advantage of low acoustic impedance and the convenience to be attached to or detached from a commercial flat transducer. Phantom experiments have been carried out to demonstrate the improvement of using such a liquid lens over using a bare transducer for PA tomography.

The integration of optical components into microfluidic systems has the potential to reduce the amount of bulky external devices and thus reduce the cost. However, one of the challenges of this concept is the accurate alignment of the optical path among multiple optical components inside a chip. We propose a tunable micro-optofluidic prism based on the liquid-core liquid-cladding structure formed in a sector-shape chamber. The optical interface of the prism is maintained in a straight line shape by distributing a row of pressure barriers in the chamber. By adjusting the flow rate ratio between core and cladding streams, the apex angle of the prism can be tuned accordingly. As a consequence, the deviation angle of the light beam refracted by the prism can be changed continuously. This tunability of our optofluidic prism can be utilized for the alignment of the optical path inside a chip or for the development of optical switches.

This paper reports a novel method, opto-acousto-fluidic microscopy, for label-free detection of droplets and cells in microfluidic networks. Leveraging the optoacoustic effect, the microscopic system possesses capabilities of visualizing flowing droplets, analyzing droplet contents, and detecting cell populations encapsulated in droplets via the sensing of acoustic waves induced by the intrinsic light-absorbance of matter.