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

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 μ m width, 30 μ m depth, and 800 μ m length;  the inlet and outlet microreservoirs have a 300 x 300 μ m 2 opening;  the reaction chamber has a 200 x 200 μ m 2 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; PL spectra

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 recordingPS for optical investigations

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 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 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.