Research

Interference reflection microscopy (IRM) is a label-free optical technique that reports nanoscale thickness, morphology, and refractive index by analyzing interference between reflections at interfaces. Because IRM can be implemented on a standard wide-field fluorescence microscope and rapidly images large fields of view, it provides a powerful route to visualizing dynamic soft materials without exogenous labels.

Our group is extending IRM from a structural imaging tool into a quantitative method for monitoring real-time dynamics of multilayer membranes and thin films. We combine imaging experiments with thin-film optical modeling to relate IRM contrast to nanoscale structure and to extract quantitative information about layer number, spacing, and deformation.

Example questions and projects include:

• How do multilayer membranes swell, buckle, wrinkle, and delaminate in response to changes in ionic strength, pH, or temperature?

• How do polymer additives or charged substrates alter multilayer stability and mechanics?

• Can IRM be used to quantify dynamic processes such as film growth, dissolution, or interlayer water redistribution?

Biological membranes are dynamic assemblies in which collective lipid–lipid and lipid–protein interactions regulate transport, signaling, and energy conversion. To isolate and control these interactions, we employ simplified model systems including vesicles, supported lipid bilayers (SLBs), and stacked supported lipid bilayers (SSLBs).

SSLBs provide a unique platform that better mimics the multilamellar architectures found in native systems such as thylakoid stacks, myelin, and skin barrier membranes while retaining experimental accessibility.

Current directions include:

• Systematically varying lipid composition (charge, headgroup chemistry, saturation) to probe how intermolecular forces control stacking, morphology, and mechanical properties

• Exploring how interfacial chemistry and surface functionalization influence multilayer organization

• Coupling IRM with fluorescence microscopy and spectroscopic assays to relate nanoscale structure to permeability, elasticity, and phase behavior

These studies aim to establish design rules for constructing functional thin films and bio-inspired membrane materials.

Thylakoid membranes house the molecular machinery of photosynthesis and possess a lipid composition that is distinct from most biological membranes, being enriched in galactolipids with non-bilayer-forming tendencies. How these unique lipids influence membrane architecture, protein organization, and photochemical stability remains an open question.

Our group builds minimal model thylakoid membranes using vesicles, SLBs, and SSLBs containing native lipid mixtures and photosynthetic pigments. Using IRM, fluorescence microscopy, and spectroscopic assays, we investigate how membrane composition governs stacking, curvature, phase behavior, and responses to photo-oxidative stress.

Representative questions include:

• How do thylakoid lipids regulate membrane curvature and multilamellar architecture?

• How does photooxidation of unsaturated lipids alter membrane morphology and stability?

• How do antioxidant pigments protect membranes from photo-oxidative damage?

Longer-term efforts will incorporate light-harvesting proteins into model membranes to directly link lipid environment to light-harvesting and dissipation processes.