43 research outputs found
A new diamond biosensor with integrated graphitic microchannels for detecting quantal exocytic events from chromaffin cells
The quantal release of catecholamines from neuroendocrine cells is a key
mechanism which has been investigated with a broad range of materials and
devices, among which carbon-based materials such as carbon fibers, diamond-like
carbon, carbon nanotubes and nanocrystalline diamond. In the present work we
demonstrate that a MeV-ion-microbeam lithographic technique can be successfully
employed for the fabrication of an all-carbon miniaturized cellular bio-sensor
based on graphitic micro-channels embedded in a single-crystal diamond matrix.
The device was functionally characterized for the in vitro recording of quantal
exocytic events from single chromaffin cells, with high sensitivity and
signal-to-noise ratio, opening promising perspectives for the realization of
monolithic all-carbon cellular biosensors
Experimental and Numerical Study of the Effect of Surface Patterning on the Frictional Properties of Polymer Surfaces
We describe benchmark experiments to evaluate the frictional properties of
laser patterned low-density polyethylene as a function of sliding velocity,
normal force and humidity. The pattern is a square lattice of square cavities
with sub-mm spacing. We find that dynamic friction decreases compared to
non-patterned surfaces, since stress concentrations lead to anticipated
detachment, and that stick-slip behavior is also affected. Friction increases
with humidity, and the onset of stick-slip events occurs in the high humidity
regime. Experimental results are compared with numerical simulations of a
simplified 2-D spring-block model. A good qualitative agreement can be obtained
by introducing a deviation from the linear behavior of the Amontons-Coulomb law
with the load, due to a saturation in the effective contact area with pressure.
This also leads also to the improvement of the quantitative results of the
spring-block model by reducing the discrepancy with the experimental results,
indicating the robustness of the adopted simplified approach, which could be
adopted to design patterned surfaces with controlled friction properties