This work introduces an environmentally benign and degradable elastomer, poly(glycerol sebacate) with calcium carbonate (PGS-CaCO 3 ), for use in soft robotics. Development of greener materials like PGS-CaCO 3 contributes to robot designs that do not require retrieval and can safely degrade in the natural environment. A simplified synthesis method of PGS was used to create elastomer sheets, which were laser cut/rastered then laminated with cyanoacrylate glue into pneumatic soft actuators. The modified polymer synthesis method is accessible for roboticists and the three chemicals used are non-hazardous and inexpensive. Three accordion-style pneumatic actuators (3, 4 and 5 chambers) were characterized for free displacement and blocked force in both linear extension and curling motions, and an additional four 3-chambered actuators were also tested to leakage and failure. Material characterization of PGS-CaCO 3 samples of all ages gave: ultimate tensile strength (UTS) from 48 to 160 kPa, elongation percent at UTS from 157 to 242%, moduli from 45 to 154 kPa, average resilience of 88% at 100 cycles, and maximum compressive force of 246 N at 50% strain. After being in an approximately 50-55 C compost pile for 7 days, the polymer visibly degraded and had an average mass loss of 20% across 12 samples. PGS's strength, elasticity, biodegradability and chemical safety make it a desirable option for roboticists looking to leverage sustainable materials. PGS may also prove a potential green alternative for robotics applications in ubiquitous environmental and infrastructure sensing.

This paper introduces preliminary work on a UV-curable, environmentally benign and degradable elastomer, poly(glycerol sebacate itaconate), or PGSI, for use in soft robotics. A one-pot, solvent-free synthesis route using safe and inexpensive chemical reagents was developed to enable easy adoption into soft robotics labs. Material characterization of non-aged PGSI samples gave: ultimate tensile strength (UTS) ranging from 134 to 193 kPa with moduli ranging from 57 to 131 kPa and elongations at break ranging from 105 to 137 % (12 samples from 6 batches tested), and resilience values ranging from 73 to 82 % (3 samples from 3 batches tested). FTIR analysis showed a possible decrease in carbon-carbon double bonds after UV curing, evidencing a decrease in itaconic acid methylene groups from photoinitiated free radical cross-linking. NMR on the pre-polymer suggested incorporation of itaconic acid into the main polymer chain and evidence of heterogeneity of the polymer backbone resulting from glycerol bonding. An example molded soft pocket pneumatic actuator is created and briefly characterized. With further development, PGSI can be a degradable material to incorporate into temporary soft robots.

Robust drug and gene delivery systems require innovative methods to control payload release and tune delivery efficiency. The most promising delivery materials are lipid-based and their efficiency often hinges on structural transformations activated by endogenous pH changes. Exogenously driving phase transitions in lipid assemblies is a tantalizing idea that could lead to better control of cargo release dynamics. Multiple reports have demonstrated phase transitions induced in lipid systems, achieved via plasmonic heating of entrained gold nanorods. However, undesirable nonlocalized heating is common due to the size mismatch between the nanorods and the lipid architecture in these systems. Lipid assemblies often exhibit lattice dimensions of just a few nanometers, rendering gold particles challenging to integrate due to their incommensurate sizes, especially in lipid nanoparticle or colloidal forms. We investigate these processes using a judiciously chosen ternary lipid system with entrained small gold nanorods that undergoes transitions between bicontinuous cubic and inverse hexagonal phases on exposure to near-infrared light. Utilizing small-angle X-ray scattering alongside electron reconstruction, we show that gold nanorods integrate into the lipid assembly core lattice by colocalizing in the water nanochannels. We also found that plasmonically activated transformations occur in a couple of minutes and are reversible.

Bilayer systems comprising lipid mixtures are the most well-studied model of biological membranes. While the plasma membrane of the cell is a single bilayer, many intra- and extra-cellular biomembranes comprise stacks of bilayers. Most bilayer stacks in nature are periodic, maintaining a precise water layer separation between bilayers. That equilibrium water separation is governed by multiple inter-bilayer forces and is highly responsive. Biomembranes re-configure inter-bilayer spacing in response to temperature, composition, or mass transport cues. In synthetic bilayer systems for applications in cosmetics or topical treatments, control of the hydration level is a critical design handle. Herein we investigate a binary lipid system that leverages key inter-bilayer forces leading to unprecedented levels of aqueous swelling while maintaining a coherent multilamellar form. We found that combining cationic lipids with bicontinuous cubic phase-forming lipids (lipids with positive Gaussian modulus), results in the stabilization of multilamellar phases against repulsive steric forces that typically lead to bilayer delamination at high degrees of swelling. Using ultra-small-angle X-ray scattering alongside confocal laser scanning microscopy, we characterized various super-swelled states of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and glycerol monooleate (GMO) lipids, as well as other analogous systems, at varied concentration and molar ratios. Through these experiments we established swelling profiles of various binary lipid systems that were near-linear with decreasing lipid volume fraction, showing maximum swelling with periodicity well above 200 nanometers. Graphic abstract Confocal fluorescence micrograph of super-swelled multilamellar structures in 90GMOD sample at 25 mM concentration. Inset plot shows intensity profile of orange line, with pink triangles indicating maxima.