Design of a Magnetic Soft Inchworm Millirobot Based on Pre-Strained Elastomer with Micropillars.

Rather than using longitudinal "muscle" as in biological inchworm, the existing magnetic active elastomer (MAE)-based inchworm robots utilize magnetic torque to pull and push the soft body, which hinders its locomotion mobility. In this paper, a new pre-strained MAE inchworm millirobot with micropillars is proposed. The pre-strained elastomer serves as a pre-load muscle to contract the soft body, and the micropillars act as tiny feet to anchor the body during the locomotion. The proposed magnetic inchworm robot features a simple fabrication process that does not require special magnetization equipment. For the first time, the pre-load muscle is introduced in the design of magnetic inchworm robots, making it more like a real inchworm in terms of locomotion mechanism. The locomotion principle and parametric design for the desired locomotion performance have been investigated. Experimental results show that the fabricated magnetic inchworm robot (size: 10 mm × 5 mm, micropillars length: 200 µm, and mass: 262 g) can locomote on a smooth acrylic surface (roughness of 0.3 µm) at the speed of 0.125 body lengths per second, which is comparable with the existing magnetic inchworm robots. Moreover, the locomotion capabilities of the inchworm robot on wet surfaces and inclined planes have been verified via experimental studies.

Macromolecular crowding and membrane binding proteins: The case of phospholipase A1.

Cells contain high levels of macromolecular crowding; understanding how macromolecular crowding impacts the behaviour of biological systems can give new insights into biological phenomena and disease pathologies. In this study, we assess the effect of macromolecular crowding on the catalytic activity of the biomembrane binding protein phospholipase A1 (PLA1). Using 3D-printed equilibrium dialysis chambers we show that macromolecular crowding increases the binding of PLA1 to lipid vesicles. However, using a mass spectrometry assay of the hydrolysis of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) by PLA1 we surprisingly find that macromolecular crowding decreases the reaction rate and causes early cessation of the catalytic activity of PLA1. Using kinetic equilibrium modelling, we are able to estimate the effect of macromolecular crowding on the association and dissociation rate constants for PLA1 binding to the lipid vesicles. These data, coupled with particle sizing measurements enable us to construct a model to explain the early cessation of catalytic activity of PLA1 with increasing levels of macromolecular crowding. This model suggests that compositional changes in the membrane, due to PLA1 action, lead to the formation of larger vesicles, which deactivate the protein. This process is more rapid in the presence of macromolecular crowding agents, suggesting that a more detailed understanding of the effects of macromolecular crowding on membrane dynamics is required to understand membrane interacting proteins in macromolecularly crowded environments. The implications of this discovery are significant given the wide range of roles of membrane fusion and fission in neurocognitive processes and the failure of these processes in neurodegenerative diseases.