Elektronika 2010-11.pdf - Instytut Systemów Elektronicznych ...

Fig. 2. Block scheme of the device for quality assessment
of oocyte by spectrophotometric characterization
Rys. 2. Schemat blokowy urządzenia do jakościowej oceny oocytów
metodą spektrofotometryczną
methodology will give an information about optical properties
of the characterized material. Obtained data will be in form of
numbers giving to an operator objective assessment of the
development competence of the reproductive cell. On the stage
of investigations, results of the analyze will be compared
to a reference methodology of classification of the biological
material based on the morphological criteria determined during
observation under optical microscope.
To realize presented above scenario a novel system utilizing
spectrophotometric methodology and lab-on-a-chip must
be built. Block scheme of the system is shown on Fig. 2.
Heart of this system is the lab-on-a-chip enabling optical
characterization of the single cell.
Lab-on-a-chip
Lab-on-a-chip contains measurement cell, net of microchannels
and passive valves for steering of fluid and oocyte/embryo
flow, and inlet/outlet holes for biological material introduction/extraction
and steering port (Fig. 3). The biological material is introduced
into the measurement cell by inlet 1, than passes through
set of passive Tesla valves (1 st check valves). Next, characterized
oocyte flows into the measurement cell by sucking of the fluid
by a pipette connected to the steering port of the chip. Topology
of the measurement cell ensures mechanical immobilization
of the cell between two optical fibers. After characterization the
material is flashed back to the outlet 1 by passing through the
second set of Tesla valves (2 nd check valve). Proposed configuration
enables steering of the fluid flow and examined biological
material transport with separation of the inlet and outlet.
The microfluidic channels and channels for optical fibers (all
140 mm depth) are etched simultaneously in DRIE (Deep Reaction
Ion Etching) process in the 380 mm – thick monocrystalline
silicon wafer (Fig. 4a). After etching, 0,3 mm – thick thermal
silicon oxide is formed to passivate chemically surface of the
chip. Next, the wafer is anodically bonded (450 0 C, 1,5 kV) to
a borosilicate glass (Borofloat Schott, Germany) with previously
mechanically drilled inlet and outlet via – holes. Following, optical
fibers with outer diameter of 125 mm and 100 mm core
(Ocean Optics, USA) are mounted. Fronts of the fibers are perfectly
aligned each to other thanks to high precision of DRIE
etching. Fibers are aligned to the edge of microfluidical channel,
ensuring immobilization of the oocyte without its mechanical destruction
(Fig. 4b). Fibers are fixed by use of UV epoxy hard glue
(NOA 61, THORLABS, Sweden). Off-chip ends of both fibers
are finished with standard SMA 905 connectors compatible with
optical connections of the lamp and the spectrometer.
The steering port inlet is finished with glued precise plastic
connector (UpChurch, USA) enabling tight positioning of
an end of the pipette. Assembled silicon-glass chip is placed
on a PCB board and than in a metal package (Fig. 5). The
metal package is small and shock resistant. It ensures stable
positioning under microscope, safe transport and performing
measurements outside laboratory, for example in a farm.
Fig. 3. Layout of the lab-on-a-chip with integrated passive valves
Rys. 3. Topologia lab-on-chipa ze zintegrowanymi zaworami pasywnymi
Fig. 5. Assembled in the metal package lab-on-a-chip for optical
characterization of the oocyte
Rys. 5. Lab-on-chip po montażu w metalowej obudowie
a) b)
Fig. 4. Lab-on-a-chip: a) view of the silicon chip after DRIE etching in comparison to a mosquito (left picture) and enlarged view of
the central part of the chip with etched measurement cell and net of Tesla valves (right picture), b) view of the measurement cell with
mounted optical fibers
Rys. 4. Lab-on-chip: a) widok chipa krzemowego po trawieniu DRIE w porównaniu do komara (lewe zdjęcie) oraz powiększony obszar
centralnej części chipa z wytrawioną komorą pomiarową oraz siecią zaworów typu Tesla (prawe zdjęcie), b) widok komory pomiarowej
z zamontowanymi światłowodami
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