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Supported lipid bilayers are often used as model systems for studying interactions of biological membranes with protein or nanoparticles. A supported lipid bilayer is a phospholipid bilayer built on a solid substrate. The latter is typically made of silica or a metal oxide due to the ease of its formation and range of compatible measurement techniques. Recently, a solvent-assisted method involving supported lipid bilayer formation has allowed the extension of compatible substrate materials to include noble metals such as gold. Here, we examine the influence of substrate composition (SiO2 vs Au) on the interactions between anionic ligand-coated Au nanoparticles or cytochrome c and zwitterionic supported lipid bilayers using quartz crystal microbalance with dissipation monitoring. We find that anionic nanoparticles and cytochrome c have higher adsorption to bilayers formed on Au relative to those on SiO2 substrates. We examine the substrate-dependence of nanoparticle adsorption with DLVO theory and all-atom simulations, and find that the stronger attractive van der Waals and weaker repulsive electrostatic forces between anionic nanoparticles and Au substrates vs anionic nanoparticles and SiO2 substrates could be responsible for the change in adsorption observed. Our results also indicate that the underlying substrate material influences the degree to which nanoscale analytes interact with supported lipid bilayers; therefore, interpretation of the supported lipid bilayer model system should be conducted with understanding of support properties.
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This content will become publicly available on March 1, 2026
An analytical model for the bending and reaction force of hygroscopic bilayers upon water adsorption
Hygroscopic bilayers replicating the morphing capability of plants upon hydration (e.g., pinecone scales, chiral seed pods) have gained much attention in robotics and material science research in the past decade. Due to variations in humidity, hygroscopic bilayers – comprising a passive substrate and an active porous coating – can convert the chemical potential difference of adsorbate species between the surrounding environment and the pore space to mechanical energy, resulting in development of curvature and forces. In this paper, we present a closed-form analytical model that considers the pore structure of the active layer for predicting the morphing of hygroscopic bilayers subjected to adsorption. For free-end cases, the curvature evolution as a function of relative humidity is predicted by combining a bilayer beam theory and a linear surface poroelasticity model for the active porous layer. For fixed-end scenarios, the reaction force generated by the bilayer is predicted using Castigliano’s second theorem with the same constitutive model. For validation, we consider two types of hydroscopic bilayers with microporous and mesoporous coatings, as tested by Boudot et al. (2016). A new isotherm equation is introduced to capture the adsorption characteristics of mesoporous media at all humidity levels. The predicted curvature and reaction force curves compared well against the experimental data. Finally, the effects of substrate Young’s modulus and the coating’s thickness on the response of the bilayer are studied. The proposed model offers straightforward mechanistic description of hydroscopic bilayers, thereby aiding in the future optimization and design of these systems for engineering applications.
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- Award ID(s):
- 2113474
- PAR ID:
- 10649087
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- International Journal of Solids and Structures
- ISSN:
- 1879-2146
- Subject(s) / Keyword(s):
- Hygroscopic Actuator Bilayer Adsorption Poromechanics Porous media
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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