Improved capillaries connection to a continuous flow

Improved capillaries connection to a continuous flow glass micromachined micro-cell W. Vastarella1, L. Nardi1, A. Masci1, M. Ilie1,3, V. Foglietti2, E. Cianci2, A. Minotti2, R. Pilloton1 1

ENEA, SP061, Via Anguillarese, 301, 00060 Santa Maria di Galeria, Rome, Italy

2

Istituto di Fotonica e Nanotecnologie IFN / CNR, Via Cineto Romano 42, 00156 Roma, Italy.

3

University ‘Politehnica’ of Bucuresti, P.O. Box 15-135, O.P.15, Romania

Target

Smoothing the walls of the inlet and outlet openings, increasing the reliability of the capillaries connection, avoiding bubbles formation

Proposed solution

Lithography on photosensitive glass (Foturan®),, in house made borosilicate glass lean adaptors for the capillaries, araldite based glue

Key process steps

Thermal annealling of the Foturan glass; obtaining of the glass lean adaptor; alignment of the parts (reservoir, cover with openings, adaptor with capillary)

A. Previously obtained connections of capillaries with the openings etched in the borofloat glass cover The process

The disadvantages

The micro-cell consists of an array of gold electrodes covered by a glass reservoir

Technological steps

1 mm

0.9 mm

The electrodes have been patterned by means of optical lithography on layers obtained by evaporation or chemical vapor deposition techniques. The glass cover reservoir ( 600 nl capacity, 0.15 mm depth) has been manufactured by means of wet etching of borofloat glass through a lithographically The micro-cell with electric patterned Au/Cr mask and fluidic connections

The advantage

b

a Top view and schematic transversal view of the opening: D=0.65 mm; d=0.45 mm; D’=0.6 mm

c

d

Lateral view (a) and top view (b) of the connection made of silicone adaptors and glued with silicone paste. Top view (c,d) of the silicone adaptors: the irregularities allow the glue expansion to close the opening

The smooth glass surface after the isotropic wet etching with an aspect ratio of 1:1 (SEM micrograph)

B. Improved fluidic connections The process

The improvements

The problems

UV-Exposure at a wavelength between 290 - 330 nm. Material thicknesses 0.4 mm.; energy density: 7 J/cm -70 J/cm

2

2

…

… The array of electrodes covered by two glass slides: one contains the reservoir and the second contains the openings

Both capillaries and glass adaptors are glued with polyimide

The roughness of the etched surface

During the UV exposure step silver atoms are formed in the o

illuminated areas. During the heat treatment between 500 (1h) o

and 600 C (1h) the glass crystallizes around these silver atoms.

…

The crystalline regions, when etched with a 10% solution of hydrofluoric acid at room temperature, have an etching rate up to 20 times higher than that of the vitreous regions.

The micro-cell with fluidic connections

The technological steps include the lithography of the photosensitive glass for the obtaining of both reservoir and cover with openings

Exploded view of the connection and schematic transversal view of the opening ( diameter 0,4mm) 1-array of electrodes on silicon wafer; 2-reservoir; 3-cover with openings

Glass adaptors glued with araldite teflon tubes inserted

The alignment error

Conclusions !A micro-cell with continuous flow of the analyte has been obtained, with a volume of 0.0006 ml and with vertical connections of capillaries (with outer diameters of 0.4 – 0.8 mm), that allows a 0.01 ml /min analyte flow !The reservoir (divided in two parts) has been obtained by micromachining of Foturan® glass !The capillaries have been inserted in the reservoir openings and fixed by means of glass adaptors with cylindrical -conical shape; the formers have been glued on the glass surface by means of a araldite-based adhesive !An in-house technique has been developed for manufacturing the glass adaptors and for aligning the parts.

ACKNOWLEDGMENTS The authors acknowledge "Progetto 5% Nanotecnologie" of MURST, Italian Fund for Research (FISR), Theme 4 “Optical and ElectroOptical Sensors”, Italian Fund for Fundamental Research (FIRB) and CoSMiC (ENEA target project on Biosensors and Bioelectronics) for financially sustaining this work.