Vacuum pickup assemblies for picking up articles and minimizing contamination of the articles are described. The neuronal cell is positioned on the substrate in a predefined orientation. Upon shielding the cell from exposure, the state change is ascertained by a cell measurement component to determine a digital value representative of the input signal amplitude at exposure. A rotor retaining member has an annular outer surface terminating at an arcuate peripheral edge, and comprises a second bearing seat.