Other Projects

Biological imaging using CARS

Cytosolic lipids participate in the growth, development, and overall health of mammalian oocytes including many roles in cellular homeostasis. It is therefore important to quantitate and compare how lipid content relates to cellular structure, function, and normalcy. We demonstrated that nonlinear vibrational microscopy (e.g., coherent anti-Stokes Raman scattering or CARS microscopy) can be used for live-cell imaging to quantify and compare lipid content in mammalian oocytes during development and in relation to body composition, and compared its efficacy to methods involving cellular fixation and staining protocols. Such a method of live-cell lipid quantification has i) experimental power in basic cell biology, ii) practical utility for identifying developmental predictive biomarkers while advancing biology-based oocyte/embryo selection, and iii) ability to yield rationally supporting technology for decision-making in rodents, domestic species, and human assisted reproduction and/or fertility preservation.

Nanomaterial – cell membrane interactions

Nanomaterials have been widely used as medicines and drug delivery vehicles. They can enter into cells through different pathways, e.g., endocytosis or direct penetration through cell membranes. We applied SFG to study molecular interactions between various nanoparticles and model cell membranes (e.g., solid supported lipid bilayers). It was found that gold nanoparticles can induce flip-flop of the lipid bilayer, and the size of the particle does not influence such flip-flop rates. We also studied the effect of surface charge of gold nanoparticles on their interactions with model cell membranes. In addition, our studies on silver nanoparticle-model cell membrane demonstrated that silver nanoparticles can also induce lipid bilayer flip-flop, and they can aggregate.

SHG imaging on flux residue

Flux materials are ubiquitously utilized in the microelectronics industry during backend processing. The copper oxides or organic solderability preservative (OSP) present on copper posts used in flip-chip packages must be removed by flux before solder reflow and die attachment to ensure a quality connection between substrate and die. However, flux residues can cause solder bridging, which renders the device useless. These residues must be studied in situ at the exposed and buried interface to determine the fundamental interactions and the distribution of flux molecules. In this work, model flux residues were investigated at the surface and the buried epoxy interface with second harmonic generation (SHG) microscopy. By mapping out the distribution of flux molecules on the surface or buried interface we will develop a better understanding of the fundamental interactions that are relevant to these systems. This work is a step forward on flux residue analysis and will help the industry better understand molecular level details of commonly used processes.