Microalgae on display: a microfluidic pixel-based irradiance assay for photosynthetic growth

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.