Digital mirror device combined with microscopy technique illuminates biological mechanisms

By exciting a sample with a high-contrast, high-frequency illumination patterns, structure illumination microscopy (SIM) serves as a fast, high-resolution imaging technique that is ideal for biological applications.

Traditionally, fast pattern switching for SIM is generated by laser interference, which has been used to image mitochondrial interactions and endoplasmic reticulum dynamics. To help improve this technique and achieve low-cost, high-resolution live cell imaging, Li et al. combined SIM with laser interference and a digital mirror device (LiDMD), which can provide the necessary rapid switching of illumination patterns.

Their customized LiDMD-SIM imaging system can supply nine different illumination patterns with a factor of 2 improvement in lateral resolution. In testing the system’s applicability for biological sample imaging, the authors found the reconstructed image could resolve features that were indistinguishable with previous methods.

While DMD is more cost effective, DMD can only reflect light at a high efficiency if the incident angle of the light and its wavelength are properly tuned to each other. This leads to a pair of identical high-intensity beams that interfere to form the desired illumination pattern.

Looking ahead, the authors propose a four-color imaging technique using different DMD states to help study intracellular organelle interactions. These interactions are tricky due to the fixed relationship between the allowed wavelength and light angle of incidence.

“To fulfill this goal, we are carrying an ongoing project in which multiple lasers are employed in the LiDMD-SIM for polarized, multi-color SIM imaging of live cells,” said author Peng Xi.

Source: “Structured illumination microscopy using digital micro-mirror device and coherent light source,” by Meiqi Li, Yaning Li, Wenhui Liu, Amit Lal, Shan Jiang, Dayong Jin, Houpu Yang, Shu Wang, Karl Zhanghao, and Peng Xi, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0008264 .