Time-resolved SICM principle and implementation.
(a) Illustration
of the SICM principle. (b) Schematic rendering of a cross-section
of the time-resolved SICM system based on a high-bandwidth large-range
SICM actuator (1), integrated into a miniature incubator (2). Nanopipettes
are fabricated through laser pulling (50 nm radius) and are successively
shrunk through scanning electron microscopy (SEM) radiation to a sub-10-nm
pore radius, shown in SEM images (3). Scale bars, 50 nm. (c) SICM
interaction curve (top) and actuator motion dynamics (bottom), with
the conventional hopping mode in blue and with the time-resolved SICM
implementation (adaptive hopping mode and data-driven controller)
in red. One kilohertz hopping rate, 1 μm hopping height, and
98% set point. (d) Actuator hopping rate performance with the conventional
hopping mode (blue), adaptive hopping mode (green), and adaptive hopping
mode together with data-driven controller (red). One micrometer hopping
height and 99% set point. (e) Die micrograph of custom TIA composed
of a low-noise operational amplifier and a pseudoresistor in its feedback.
The pseudoresistor consists of N series-connected pMOS transistor
pairs with specific biasing to achieve a large and precise resistance
value. (f) Transimpedance measurements of the 1st stage TIA (blue)
and the overall transimpedance using the subsequent amplifier stage
for bandwidth extension (red).