Kelly Parker defends dissertation

Kelly Parker defended her dissertation entitled "Soft Microscopy: Enhancing Imaging for the High-Throughput Characterization of Soft Materials". Kelly has been with Northwestern University and the VPD Group since 2016 and focuses on advanced sample preparation and microscopy methods to image soft materials, particularly small biological molecules such as proteins and protein assemblies.

Here is a summary of her dissertation:

The imaging of soft and biological materials, or “soft microscopy,” is essential to the understanding of their structure and its relationship to their function. Two challenges arise when imaging soft materials: they have inherently low contrast because of their low atomic number and electron density, and they are susceptible to beam damage. This work aims to improve soft microscopy through contrast enhancement by a variety of methods, beginning with sample preparation, continuing through the choice of imaging modality, and ending with post-processing. The core focus of this dissertation is improving contrast by decreasing the voltage, and therefore energy, of the electron beam, which increases the probability that electrons will undergo a scattering event before transmission. Imaging at voltages below those typically operable in a TEM instrument is accomplished by performing transmission imaging in a scanning electron microscope, or STEM-in-SEM. This method offers high contrast and resolution for the imaging of soft, biological and hybrid structures, is high-throughput because of the nature of SEM sample exchange, and is low-cost and user-friendly compared to TEM-based methods. STEM-in-SEM also allows for multi-signal imaging that takes advantage of the multitude of signals available in SEM, particularly backscattered electron imaging and x-ray spectroscopy for elemental analysis. The benefits of STEM-in-SEM and associated techniques were demonstrated for a variety of soft and hybrid structures from the nanoscale to the microscale, highlighting the effectiveness of low-voltage analysis in the field of soft microscopy.