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.

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.

Abstract:The satellite clocks used in the BeiDou-2 satellite navigation System (BDS) are Chinese self-developed Rb atomic clocks, and their performances and stabilities are worse than GPS and Galileo satellite clocks. Due to special periodic noises and nonlinear system errors existing in the BDS clock offset series, the GPS ultra-rapid clock model, which uses a simple quadratic polynomial plus one periodic is not suitable for BDS. Therefore, an improved prediction model for BDS satellite clocks is proposed in order to enhance the precision of ultra-rapid predicted clock offsets. First, a basic quadratic polynomial model which is fit for the rubidium (Rb) clock is constructed for BDS. Second, the main cyclic terms are detected and identified by the Fast Fourier Transform (FFT) method according to every satellite clock offset series. The detected results show that most BDS clocks have special cyclic terms which are different from the orbit periods. Therefore, two main cyclic terms are added to absorb the periodic effects. Third, after the quadratic polynomial plus two periodic fitting, some evident nonlinear system errors also exist in the model residual, and the Back Propagation (BP) neural network model is chosen to compensate for these nonlinear system errors. The simulation results show that the performance and precision using the improved model are better than that of China iGMAS ultra-rapid prediction (ISU-P) products and the Deutsches GeoForschungsZentrum GFZ BDS ultra-rapid prediction (GBU-P) products. Comparing to ISU-P products, the average improvements using the proposed model in 3 h, 6 h, 12 h and 24 h are 23.1%, 21.3%, 20.2%, and 19.8%, respectively. Meanwhile the accuracy improvements of the proposed model are 9.9%, 13.9%, 17.3%, and 21.2% compared to GBU-P products. In addition, the kinematic Precise Point Positioning (PPP) example using 8 Multi-GNSS Experiment MGEX stations shows that the precision based on the proposed clock model has improved about 16%, 14%, and 38% in the North (N), East (E) and Height (H) components.

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.