23,046 research outputs found
TIR-based dynamic liquid-level and flow-rate sensing and its application on centrifugal microfluidic platforms
For the first time we present a technique for the spatio-temporally resolved localization of liquid-gas interfaces on centrifugal microfluidic platforms based on total internal reflection (TIR) at the channel wall. The simple setup consists of a line laser and a linear image sensor array mounted in a stationary instrument. Apart from identifying the presence of (usually unwanted) gas bubbles, the here described online meniscus detection allows to measure liquid volumes with a high precision of 1.9%. Additionally, flow rates and viscosities (range: 1-10.7 mPa s) can be sensed even during rotation at frequencies up to 30 Hz with a precision of 4.7% and 4.3%, respectively
Sol-Gel Derived Ferroelectric Nanoparticles Investigated by Piezoresponse Force Microscopy
Piezoresponse force microscopy (PFM) was used to investigate the
ferroelectric properties of sol-gel derived LiNbO nanoparticles. To
determine the degree of ferroelectricity we took large-area images and
performed statistical image-analysis. The ferroelectric behavior of single
nanoparticles was verified by poling experiments using the PFM tip. Finally we
carried out simultaneous measurements of the in-plane and the out-of-plane
piezoresponse of the nanoparticles, followed by measurements of the same area
after rotation of the sample by 90 and 180. Such
measurements basically allow to determine the direction of polarization of
every single particle
- âŠ