Imaging liquids using microfluidic cells

Chemistry occurring in the liquid and liquid surface is important in many applications. Chemical imaging of liquids using vacuum-based analytical techniques is challenging due to the difficulty in working with liquids with high volatility. Recent development in microfluidics enabled and increased our capabilities to study liquid in situ using sensitive techniques such as electron microscopy and spectroscopy. Due to its small size, low cost, and flexibility in design, liquid cells based on microfluidics have been increasingly used in studying and imaging complex phenomena involving liquids. This paper presents a review of microfluidic cells that were developed to adapt to electron microscopes and various spectrometers for in situ chemical analysis and imaging of liquids. The following topics will be covered, including cell designs, fabrication techniques, unique technical features for vacuum compatible cells (e.g., detection windows, device materials), and imaging with electron microscopy and spectroscopy. Challenges are summarized and recommendations for future development priority are proposed.