Lensless, microfluidic imaging of cells and tiny worms

In scanning microscopy, images are put together by sweeping a single narrow beam back and forth over a sample. If you had a wide array of multiple beams, one scan would suffice. And if the sample moved over the array, you wouldn’t need to scan at all. That idea is behind a new optofluidic imaging scheme developed for biological applications by Caltech’s Changhuei Yang and his colleagues. At the heart of the scheme is an off-the-shelf sensor whose CMOS pixels are read out individually. Contrast is achieved when a sample, under constant illumination, momentarily shadows the pixels as it passes over them in a microfluidic channel. At 10 × 10 μm², the pixel size is too big to resolve the parts of amoebae and other tiny organisms. To boost the resolution, Yang masks the pixels with a commensurate array of 1-μm-diameter holes. Although 99% of...