Microfluidic components 2018 sami franssilaaalto fi Contents Pumping

Microfluidic components 2018 sami. franssila@aalto. fi

Contents • • • Pumping Valving Dosing Mixing Surface microfluidics • • Fuel cells Microreactors Droplet reactors Cellomic devices flow control applications

Pumps • • bubble pumps membrane pumps diffuser pumps rotary pumps electrohydrodynamic electro-osmotic/electrophoretic ultrasonic pumps vacuum pumps

Pumps: actuation mechanisms

Peristaltic pump = 3 valves in series

Pumps without moving parts Surface tension driven pump Electro-osmotic pump Nozzle-diffuser pump, Olsson, Stemme 1997

Osmotic pump for drug delivery

Thermal ink jet MEMS Handbook

Passive • mechanical • geometric • hydrophobic Active valves pneumatic thermopneumatic phase-change electrostatic piezoelectri thermal expansion

Quake valve

Why semicircular channel ? How to make semicircular channel ? Resist flow > Tg

PDMS membrane valve Lab Chip, 2010, 2814 -2817

Bossed valve

Flap valve by PDMS molding

Flap-valve (2)

Geometric valves Pillar “forest” controls the rate of capillary flow. Rapid constriction of the flow channel will stop the flow. Side channel offers timing of flow. Transducers 2005, p. 1565

Microreactors Small volume good if expensive and/or dangerous chemicals Fast reactions because small diffusion distances Large surface area (either positive or negative effect) Good temperature control and fast ramp rates Besser: J. Vac. Sci. Technol. B 21. 2. , Mar/Apr 2003 Good flow control because of laminar flow

Microreactor in silicon

High pressure reactor Tiggelaar

Electrowetting (EWOD) Electrowetting: electrostatically induced reduction in the contact angle of an electrically conductive liquid droplet on a surface.

Electrowetting (2) Young-Lippmann equation: d is the thickness of the dielectric layer and εr is its relative dielectric constant. Here, γlv is the liquid–vapor surface tension, V is the applied voltage, h is the contact angle, and ε 0 is the permittivity of free space.

EWOD device

EWOD materials

EWOD = DMF = Digital microfluidics

Droplet movement

Digital microreactor

PCR DNA copy machine

µPCR = rapid thermal ramping

Continuos flow PCR

Basic geometries: straight channel -separation channel -mixer -microreactor -. . .

Basic geometries: X, T, Y, H Applications: • CE injectors • mixers • filters • reactors

Particle filtering: H-filter

Combine basic shapes to devices Injector + separation channel precolumn reaction + separation post-column reaction

Dispensers Nguyen p.

Optoelectrofluidic chip

Electrophoresis chip with electrochemical detection

CE chip fabrication: channels in silicon (2)

CE chip fabrication: electrodes on polycarbonate (3) Lift-off

CE chip fabrication: electrodes on polycarbonate (4) Liftoff

Bond Si and PC to complete fabrication Polycarbonate Si

Adhesive bonding ”glueing” -any two materials can be joined -glue remains in the structure, and may react with chemicals -temperature is ca. 100 -200 o. C only -no pressure needed

Number of materials Substrate, cap and adhesive 3 materials Embossing without bottom clearing + direct bonding single material Adhesive and cap identical 2 materials

Materials considerations, fabrication point of view • Stresses (e. g. during curing) • Thermal stability • Outgassing/bubble formation • Thermal expansion differences • Chemicals compatibility (cleaning, etching) • Single/double side processing (e. g. smoothness)

Materials considerations, applications point of view Surface uniformity (adsorption, surface charge) Electrical/thermal insulation Transparency Autofluorescence Solvent compatibility Acid/base compatibility Permeability to gases Water intake PDMS on glass: 3 phobic walls, 1 philic wall