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Selection of high-quality sperm is critical to the success of assisted reproductive technologies. Clinical screening for top sperm has long focused on sperm swimming ability when following boundaries or when fully free of constraints. In this work, we demonstrate a sperm selection approach with parallel 2 μm tall confined selection channels that prohibit rotation of the sperm head and require planar swimming. We demonstrate that a planar swimming subpopulation of sperm capable of entering and navigating these channels has DNA integrity superior to the freely-swimming motile or raw sperm populations over a wide range of semen sample qualities. The DNA integrity of the selected sperm was significantly higher than that of the corresponding raw samples for donor samples and clinical patient samples, respectively. In side-by-side testing, this method outperforms current clinical selection methods, density gradient centrifugation and swim-up, as well as sperm selected via general motility. Planar swimming represents a viable sperm selection mechanism with the potential to improve outcomes for couples and offspring.

Cultivating microalgae has the potential to produce biofuels and bioproducts from solar energy with low land use and without competing with food crops. However, despite these key advantages, barriers remain to widespread, economical production from microalgae including: the relatively low solar energy conversion efficiency of photosynthesis, unknown optimal cultivation conditions, and the high energy and economic costs of cultivation and processing microalgal biomass. Thus, recent technological developments seek to address these barriers. To optimize cultivation conditions, devices taking advantage of advanced fluid and light handling techniques are being developed. These approaches drastically increase experimental throughput to find the ideal cultivation parameters. To apply optimal conditions, a range of cultivation approaches are being developed to deliver light and nutrients to microalgae to achieve high productivities. Finally, to extract maximal value out of microalgal biomass, downstream processing technology, such as hydrothermal liquefaction, is replacing costly conventional processes to produce fuels and high-value products from microalgae. Taken together, these technologies can allow microalgae to become competitive in the sustainable energy landscape – particularly to produce complex, high-value molecules.

Optimizing bioproduct generation from microalgae is complicated by the myriad of coupled parameters affecting photosynthetic productivity. Quantifying the effect of multiple coupled parameters in full-factorial fashion requires a prohibitively high number of experiments. We present a simple hydrogel-based platform for the rapid, full-factorial mapping of light and nutrient availability on the growth and lipid accumulation of microalgae. We accomplish this without microfabrication using thin sheets of cell-laden hydrogels. By immobilizing the algae in a hydrogel matrix we are able to take full advantage of the continuous spatial chemical gradient produced by a diffusion-based gradient generator while eliminating the need for chambers. We map the effect of light intensities between 0 μmol m(-2) s(-1) and 130 μmol m(-2) s(-1) (∼28 W m(-2)) coupled with ammonium concentrations between 0 mM and 7 mM on Chlamydomonas reinhardtii. Our data set, verified with bulk experiments, clarifies the role of ammonium availability on the photosynthetic productivity Chlamydomonas reinhardtii, demonstrating the dependence of ammonium inhibition on light intensity. Specifically, a sharp optimal growth peak emerges at approximately 2 mM only for light intensities between 80 and 100 μmol m(-2) s(-1)- suggesting that ammonium inhibition is insignificant at lower light intensities. We speculate that this phenomenon is due to the regulation of the high affinity ammonium transport system in Chlamydomonas reinhardtii as well as free ammonia toxicity. The complexity of this photosynthetic biological response highlights the importance of full-factorial data sets as enabled here.

Microalgal biofuel is an emerging sustainable energy resource. Photosynthetic growth is heavily dependent on irradiance, therefore photobioreactor design optimization requires comprehensive screening of irradiance variables, such as intensity, time variance and spectral composition. Here we present a microfluidic irradiance assay which leverages liquid crystal display technology to provide multiplexed screening of irradiance conditions on growth. An array of 238 microreactors are operated in parallel with identical chemical environments. The approach is demonstrated by performing three irradiance assays. The first assay evaluates the effect of intensity on growth, quantifying saturating intensity. The second assay quantifies the influence of time-varied intensity and the threshold frequency for growth. Lastly, the coupled influence of red-blue spectral composition and intensity is assessed. Each multiplexed assay is completed within three days. In contrast, completing the same number of experiments using conventional incubation flasks would require several years. Not only does our approach enable more rapid screening, but the short optical path avoids self-shading issues inherent to flask based systems.

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