Biomimicking of natural cellular materials

The role that microstructure plays in the mechanical efficiency of natural cellular materials is examined here. The focus of this study is on elastic behaviour. Two natural materials with microstructures resistant to local bucking: plant stems and animal quills have also been examined.

Impedance control balances stability with metabolically costly muscle activation.

Humans are able to stabilize their movements in environments with unstable dynamics by selectively modifying arm impedance independently of force and torque. We further investigated adaptation to unstable dynamics to determine whether the CNS maintains a constant overall level of stability as the instability of the environmental dynamics is varied. Subjects performed reaching movements in unstable force fields of varying strength, generated by a robotic manipulator. Although the force fields disrupted the initial movements, subjects were able to adapt to the novel dynamics and learned to produce straight trajectories. After adaptation, the endpoint stiffness of the arm was measured at the midpoint of the movement. The stiffness had been selectively modified in the direction of the instability. The stiffness in the stable direction was relatively unchanged from that measured during movements in a null force field prior to exposure to the unstable force field. This impedance modification was achieved without changes in force and torque. The overall stiffness of the arm and environment in the direction of instability was adapted to the force field strength such that it remained equivalent to that of the null force field. This suggests that the CNS attempts both to maintain a minimum level of stability and minimize energy expenditure.

Spectroscopic characteristics and cellular compatibility of protein wrapped single wall carbon nanotubes

Non-covalent functionalization of CoMoCAT single-wall carbon nanotubes (SWNTs) by bovine serum albumin (BSA) was achieved. Photoluminescence spectra for the functionalized nanotubes showed good dispersion by BSA functionalization. Raman spectra were taken for the sonicated SWNT-BSA solution to establish the signal versus concentration correlation. Cellular uptake of functionalized carbon nanotubes by mouse macrophage (RAW264.7) was then investigated using Raman spectroscopy. For a seeding density of 50% confluence in a culture solution containing 10 μg/ml of BSA-SWNTs, uptake of 200 μg/ml by the macrophages was recorded after 23hr incubation, indicating an active uptake of SWNTs. © 2012 IEEE.