Development of a new microfluidic

analysis system on silicon with different

nanostructures as sensitive elements

Mihaela Miu, Irina Kleps, Florea Craciunoiu, Monica Simion, Teodora Ignat, Adina Bragaru

NATIONAL INSTITUTE FOR RESEARCH AND DEVELOPMENT IN MICROTECHNOLOGIES - IMT BUCHAREST

–

CENTER OF NANOTECHNOLOGY

mihaelam@imt.ro

laboratory on a chip = an integrated system which transforms the

biochemical

information in an optical / electrical signal;

State of the art

substrates used for

technological

fabrication: silicon.

polymers (hydrogels and plastics);

ceramics;

glass;

detail (b)

(a)

The lay-out of a BioLab-on-a-chip

Schematic representation of a transversal section of

device structure detail – an assemble of two

components:

• the base of device includes both the microfluidic

system and sensing elements is obtained by Si

micromachining;

• the cap of device contains cavities for microrservoirs

filling and optical detection.

(b)

Microfluidic device designed and realised on Si

substrate:

the channels have 50 μm width, 30 μm depth, and 800 μm

length;

the inlet and outlet microreservoirs have a 300 x 300 μm2

opening;

the reaction chamber has a 200 x 200 μm2 opening.

Nanoelectrode arrays (NEA)

an integrate device (WE – NEAs, RE, CE) for electrochemical analyses

Nanostructures on silicon studied for applications in biology

Porous silicon (PS)

Applications:

• metallic traces detection in liquid media for

pollution control ;

• investigation of electrochemical activity in

biological media.

Applications:

• bio-optoelectronic device based on

photoluminescence phenomena of PS;

• biocompatible substrate of micro PS for cell growth;

• resorbable mesoPS implant for pharmaceutical

substances release;

AA

550 600 650 700 750 800 850 0.0

0.2

0.4

0.6

0.8

1.0 88% 82% 70% 65% 62% 60% 58%

PL

Inte

nsity

(no

rmat

e v

alue

s)

Wavelength (nm)

PL

spectra

0 20 40 60 80 100

200

300

400

500

600

700 N3Fe N1Fe

Con

cent

ratie

Fe/

PS

(g

/l)

Timp (zile)

Design of a new bioLab-on-a-chip to investigate the cells

behaviour and response to different stimuli or drug solutions:

Images of experimental basic structure – the microfluidic system

Nanostructures integrated in microreservoir for complemmentary analyses

NE for electrical signal recording

PS for optical investigations

11.. 22..

Experimental fabrication is based on standard processes from silicon technology:

• wet etching (chemical and electrochemical);

• metallization;

• dielectric deposition.

with corresponding

photolithographic processes

Technological processes introduced to integrate

the nanostructured element (PS) for optical

detection

Technological process flow for microfluidic analysis system

1.1. Microfluidic analysis system on silicon with

nanoelectrode for electrical investigation of cells reaction to

external stimuli

- experimental structures - Two photolithographic mask sets were designed, according with the nature of Si

substrate, mainly with the level of its resistivity, to define the electrical circuit:

for p-type or n-type Si, the both

electrodes have the contact pads on

the same side of the wafer;

for highly doped Si – p+ or n+ – only one

contact pad is necessary, for the

contraelectrode

NE will be contacted on the wafer back-

side and will be addressed through the

substrate

The bottom of microreactor cross-section – porous silicon structure

2.2. Microfluidic analysis system on silicon with porous

silicon for optical investigation of cell behaviour to external

stimuli

- experimental structures -

Based on previous results, PS could have two roles:

(i) support for biological or organic molecule

immobilisation;

(ii) optical biosensor for proteins, antigens and DNA.

Measurement results obtained using the experimental structures

- microfluidic analysis system on silicon with different nanostructures as sensitive

elements:1. NE 2. PS

2.2. Porous silicon promotes the adhesion process of biological material on inorganic

surface (no further coating with poly-lysine or collagen is required) and can be used

as direct fluorescence biosensor.

1.1. Nanoelectrode facilitates the recording of bioelectrochemical processes which

take place at its surface (due to cyanobacteria activity, for ex.) - it reduces noise

and improves the spatial resolution in recordings.

Conclusions:

Besides the main benefits of the miniaturised system, related to the

reducing of the sample volumes and to a shorter analysis time, the use of

nanostructures as integrated elements leads to enhancement of the

analyses sensitivity.