In vitro fertilization (IVF) therapy is an important treatment for human infertility. However, the methods for clinical IVF have only changed slightly over decades: culture medium is held in oil-covered drops in Petri dishes and manipulation occurs by manual pipetting. Here we report a novel microwell-structured microfluidic device that integrates single oocyte trapping, fertilization and subsequent embryo culture. A microwell array was used to capture and hold individual oocytes during the flow-through process of oocyte and sperm loading, medium substitution and debris cleaning. Different microwell depths were compared by computational modeling and flow washing experiments for their effectiveness in oocyte trapping and debris removal. Fertilization was achieved in the microfluidic devices with similar fertilization rates to standard oil-covered drops in Petri dishes. Embryos could be cultured to blastocyst stages in our devices with developmental status individually monitored and tracked. The results suggest that the microfluidic device may bring several advantages to IVF practices by simplifying oocyte handling and manipulation, allowing rapid and convenient medium changing, and enabling automated tracking of any single embryo development.

a This paper describes an optofluidic droplet interrogation device capable of counting fluorescent drops at a throughput of 254 000 drops per second. To our knowledge, this rate is the highest interrogation rate published thus far. Our device consists of 16 parallel microfluidic channels bonded directly to a filtercoated two-dimensional Complementary Metal-Oxide-Semiconductor (CMOS) sensor array. Fluorescence signals emitted from the drops are collected by the sensor that forms the bottom of the channel. The proximity of the drops to the sensor facilitates efficient collection of fluorescence emission from the drops, and overcomes the trade-off between light collection efficiency and field of view in conventional microscopy. The interrogation rate of our device is currently limited by the acquisition speed of CMOS sensor, and is expected to increase further as high-speed sensors become increasingly available.

BACKGROUND Sperm screening is an essential step in in vitro fertilization (IVF) procedures. The swim-up method, an assay for sperm motility, is used clinically to select the ideal sperm for subsequent manipulation. However, additional parameters, including acrosome reaction capability, chemotaxis, and thermotaxis, are also important indicators of mammalian sperm health. To monitor both sperm motility and chemotaxis simultaneously during sperm screening, we designed and constructed a microdevice comprising a straight channel connected with a bibranch channel that mimics the mammalian female reproductive tract. METHODS The width and length of the straight channel were optimized to select the motile sperms. We selectively cultured cumulus cells in the bibranch channel to generate a chemoattractant-forming chemical gradient. Sperm chemotaxis was represented by the ratio of the sperm swimming toward different branches. RESULTS The percentage of motile sperms improved from 58.5% (3.8%) to 82.6% (2.9%) by a straight channel 7 mm in length and 1 mm in width. About 10% of sperms were found to be chemotactically responsive in our experiment, which is consistent with previous studies. CONCLUSIONS For the first time, we achieved the combined evaluation of both sperm motility and chemotaxis. The motile and chemotactically responsive sperms can easily be enriched on a lab-on-a-chip device to improve IVF outcome.

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In vitro fertilization (IVF) technology has been broadly applied to solve human infertility in recent years. However, the physical tools for IVF remain unchanged over several decades before microfluidic technology was introduced in this field. Here, we report a novel microdevice that integrates each step of IVF, including oocyte positioning, sperm screening, fertilization, medium replacement, and embryo culture. Oocytes can be singly positioned in a 4 × 4 array of octacolumn units. The four symmetrical straight channels, crossing at the oocyte positioning region, allowed efficient motile sperm selection and facilitated rapid medium replacement. The fertilization process and early embryonic development of the individual zygote was traced with microscopic recording and analyzed by in situ fluorescent staining. The murine sperm motility was increased from 60.8 ± 3.4% to 96.1 ± 1.9% through the screening channels. The embryo growth rate and blastocyst formation were similar between the routine Petri dish group and the microdevice group. The healthy blastocysts developed in the microdevice could be conveniently retrieved through a routine pipetting operation and used for further embryo transfer.

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We report the implementation of an on-chip microscope system, termed fluorescence optofluidic microscope (FOFM), which is capable of fluorescence microscopy imaging of samples in fluid media. The FOFM employs an array of Fresnel zone plates (FZP) to generate an array of focused light spots within a microfluidic channel. As a sample flows through the channel and across the array of focused light spots, the fluorescence emissions are collected by a filter-coated CMOS sensor, which serves as the channel's floor. The collected data can then be processed to render fluorescence microscopy images at a resolution determined by the focused light spot size (experimentally measured as 0.65 μm FWHM). In our experiments, our established resolution was 1.0 μm due to Nyquist criterion consideration. As a demonstration, we show that such a system can be used to image the cell nuclei stained by Acridine Orange and cytoplasm labeled by Qtracker®.