(5)
Considering an average loading time of 20.4±4.1 s, we achieved a testing
per fish time of 44.4±4.8 s for the proposed quadruple-fish device which
was 60% faster than the time spent for testing in the single-fish
device[16]. Our quadruple-fish device also offered
loading and orientation efficiencies of 87.5±5.6% and 90±7.1%,
respectively. These data clearly demonstrate the advantage of our
quadruple-fish device when aiming to facilitate larger sample sizes in a
shorter period of time.
Electric current and flow field analyses were conducted using COMSOL to
ensure their uniformity throughout the device. According to the electric
simulation, applying a total electric current of 12 μA between the anode
and cathode electrodes (shown in Fig. 1A) resulted in a uniform voltage
drop of 1.1 V (as seen in trap B in Fig. 2) and electric current of 3 μA
across each trap, consistent with the current used in our previous
single-fish device[6,16].
The flow in the indirect flow channel ran opposite to that in the main
channel to generate comparable pressure drops across each TR, ensuring
uniform loading conditions. The analysis of the flow dynamics within the
chip showed a pressure drop and therefore a hydrodynamic force pointing
from the main channel towards the TRs enabling loading and
immobilization within the TRs. The pressure contour plot across each
trap closely resembled the contour shown in Fig. 2 for trap C. The shear
stress in the TRs was also obtained by multiplying the water viscosity
by the velocity gradient at the wall, as shown in trap D in Fig. 2. The
maximum shear stress experienced by zebrafish during the loading process
was 10 Pa which was less than the 45 Pa threshold to avoid injury
according to the studies done by Ulanowicz and
Morgan[35,36].