Low-cost and high-resolution on-chip microscopes are vital for reducing cost and improving efficiency for modern biomedicine and bioscience. Despite the needs, the conventional microscope design has proven difficult to miniaturize. Here, we report the implementation and application of two high-resolution (Ϸ0.9 m for the first and Ϸ0.8 m for the second), lensless, and fully on-chip microscopes based on the optofluidic microscopy (OFM) method. These systems abandon the conventional microscope design, which requires expensive lenses and large space to magnify images, and instead utilizes microfluidic flow to deliver specimens across array(s) of micrometer-size apertures defined on a metal-coated CMOS sensor to generate direct projection images. The first system utilizes a gravity-driven microfluidic flow for sample scanning and is suited for imaging elongate objects, such as Caenorhabditis elegans; and the second system employs an electrokinetic drive for flow control and is suited for imaging cells and other spherical/ellipsoidal objects. As a demonstration of the OFM for bioscience research, we show that the prototypes can be used to perform automated phenotype characterization of different Caenorhabditis elegans mutant strains, and to image spores and single cellular entities. The optofluidic microscope design, readily fabricable with existing semiconductor and microfluidic technologies, offers low-cost and highly compact imaging solutions. More functionalities, such as on-chip phase and fluorescence imaging, can also be readily adapted into OFM systems. We anticipate that the OFM can significantly address a range of biomedical and bioscience needs, and engender new microscope applications.optofluidic microscopy ͉ phenotype characterization ͉ microfluidic O ptical microscopy pervades almost all aspects of modern biomedicine and bioscience; to name a few key areas, optical microscopes are vital instruments in microorganism studies, cell biology, and clinical pathology. However, despite the long history of microscopy and the remarkable range of optical tools that have been developed since the invention of the first microscope in the early 1600s, the fundamental design of microscopes has undergone little change. A typical microscope still consists of an objective, space for relaying the image, and an eyepiece or an imaging lens to project a magnified image onto a person's retina or a camera. In addition to its relatively high implementation cost (precise and expensive lenses are needed), the conventional microscope design has also proven difficult to miniaturize (1, 2). A relatively modern invention-digital inline holographic microscopy (DIHM) (3)-showed that it is possible to render microscope-resolution images of objects without the use of lenses; however, as a method, DIHM requires significant postmeasurement computation and the use of a coherent light source. In 2005, Lange et al. (4) reported a direct projection method to implement compact and low-cost imaging systems. In Lange's method, the specimen is placed...

We report a novel microfluidics-based lensless imaging technique, termed optofluidic microscopy (OFM), and demonstrate Caenorhabditis elegans imaging with an OFM prototype that gives comparable resolution to a conventional microscope and a measured resolution limit of 490 ¡ 40 nm.Optical imaging of samples in a biological or clinical setting is generally performed with expensive and bulky microscope systems. The imaging process can be time consuming and labor intensive. A cheaper and automated microscope that is implementable on a microfluidic platform can dramatically simplify and improve imaging procedures and related applications in biomedicine.The major advantages of microfluidic devices include their compactness and low cost. While excellent solutions to a range of important miniaturization challenges, such as fluidic transportation, 1 sample manipulation, 2 chemical sensing 3 and sample sorting, 4 have all been demonstrated, sub-micron on-chip optical imaging remains an unresolved issue. The high resolution imaging requirement in existing microfluidic systems is still fulfilled by using bulky conventional microscopes, 5,6 which obviates the cost and size advantages of micro analysis systems. (As a point of reference, a commercial conventional microscope has resolution that ranges from y1 mm to 0.2 mm depending on the objective's numerical aperture and the wavelength used.) One possible low-resolution imaging strategy is to stack the sample directly on top of a two-dimensional sensor array and illuminate the sample with a uniform light field. However, the resolution of the resulting transmission image is governed by the sensor's pitch size, which is typically 5 mm or larger-achieving microscope level resolution is difficult with this method. Using this approach, Lange et al.7 demonstrated a compact, on-chip imaging device with fair resolution (.10 mm).In this Communication, we report on an on-chip high resolution and high throughput imaging technique, termed optofluidic microscopy (OFM). The OFM's resolution is not limited by the actual pixel size of the detection sensors. Our prototype is able to image micro-organisms with resolution that is comparable to a conventional microscope. Further, the OFM does not require the use of any bulk optical elements and can potentially be used to create compact systems that are only limited in size by the underlying linear array sensor.The OFM device consists of an opaque metal film with an etched array of submicron apertures and a PDMS microfluidic chip that is bonded onto the metal film. In our experiments, the fabrication of the aperture array and the microfluidic chip was carried out in two separate steps. To fabricate the aperture array, 90 nm thick aluminium was first evaporated onto a quartz wafer. Then the pattern of the aperture array (diameter D = 600 nm; spacing = 5 mm) was defined on a PMMA resist by e-beam lithography (JEOL 9300), and subsequently transferred into the aluminium layer by reactive ion etching. The microfluidic structure was fabricated on a Mic...

In this work, motivated by an approach used in a cactus to collect fog, we have developed an artificial water-collection structure. This structure includes a large ZnO wire and an array of small ZnO wires that are branched on the large wire. All these wires have conical shapes, whose diameters gradually increase from the tip to the root of a wire. Accordingly, a water drop that is condensed on the tip of each wire is driven to the root by a capillary force induced by this diameter gradient. The lengths of stem and branched wires in the synthesized structures are in the orders of 1 mm and 100 μm, respectively. These dimensions are, respectively, comparable to and larger than their counterparts in the case of a cactus. Two groups of tests were conducted at relative humidity of 100% to compare the amounts of water collected by artificial and cactus structures within specific time durations of 2 and 35 s, respectively. The amount of water collected by either type of structures was in the order of 0.01 μL. However, on average, what has been collected by the artificial structures was 1.4-5.0 times more than that harvested by the cactus ones. We further examined the mechanism that a cactus used to absorb a collected water drop into its stem. On the basis of the gained understanding, we developed a setup to successfully collect about 6 μL of water within 30 min.

Abstract. We review the current state of research in endoscopic optical coherence tomography ͑OCT͒. We first survey the range of available endoscopic optical imaging techniques. We then discuss the various OCT-based endoscopic methods that have thus far been developed. We compare the different endoscopic OCT methods in terms of their scan performance. Next, we examine the application range of endoscopic OCT methods. In particular, we look at the reported utility of the methods in digestive, intravascular, respiratory, urinary and reproductive systems. We highlight two additional applications-biopsy procedures and neurosurgery-where sufficiently compact OCTbased endoscopes can have significant clinical impacts.

Liquid drops have shown interesting behaviors between two nonparallel plates. These plates may be fixed or movable relative to each other. In this work, we also explore these behaviors through a combination of theoretical and experimental investigations and obtain some new results. We show that when the two plates are fixed, different from the previous understanding, a lyophilic drop may not necessarily fill the corner of the two plates. We also demonstrate that it may fill the corner, when more liquid is added to the drop or when the top plate is lifted. Furthermore, we propose a physical model to interpret the shifting effect of a liquid drop. This effect appears when the drop is squeezed and relaxed between two nonparallel plates, and it has been used by some shorebirds to transport prey. On the basis of the proposed model, we have found three new phenomena related to the shifting effect.