In this study, a new type of active membrane based on magnetic elastomer composite is manufactured, characterized and integrated into a simple valve. The simple and low-cost fabrication process combined with large displacement capability of the membrane is favorable for use in disposable fluidic devices. Passivated ferromagnetic cobalt nanoparticles (~37 nm) synthesized by the chemical route were embedded in polydimethylsiloxane (PDMS) to fabricate nano-composite flexible membranes. Magneto-mechanical and mechanical properties of the PDMS composite elastomeric membrane loaded with various concentrations of cobalt (Co) nanoparticles (between 15 and 75 % by weight) were studied. Dynamic mechanical analysis (DMA) measurements of the nano-composite membranes were conducted as a function of the applied frequency (between 0.1 and 56 Hz). With higher concentration (50-wt%) of Co nanoparticles in PDMS, the elastic modulus was increased by 3–4 times as compared with that of membranes with lower concentrations of nanoparticles. Shore hardness was maximum for the nano-composite membrane loaded with 50-wt% of Co nanoparticles. A fluidic actuator with 400 μm thick PDMS membrane of 18 mm free diameter loaded with 50-wt% Co nanoparticles was manufactured and tested under external magnetic field. In the region where the magnetic field gradient is highest, high deflection of the membrane could be obtained (0.68 mm for 1 Tesla). However some hysteresis of the membrane deflection could be observed, even at very low frequency. Loading of PDMS with Co nanoparticles allowed a wider range of control of the wetting properties of PDMS surfaces under oxygen plasma treatment, from hydrophobic to hydrophilic to super-hydrophilic. Tunability in hydrophilicity could be achieved by varying the process parameters as verified by contact angles and Fourier transforms infrared (FTIR) spectra before and after plasma treatment. Under certain conditions, 50 % Cobalt-PDMS membrane surfaces exhibited a super-hydrophilic behavior (contact angle ~5°).

Carbon nanotubes have attracted the fancy of many scientists since their first discovery in 1991. Their small dimensions, strength and remarkable physical properties make them a very unique material with a whole range of promising applications. The most important application of carbon nanotubes based on their important mechanical properties will be as reinforcements in composite materials, especially nanotube-filled polymer composites are an obvious materials application area. In this work, the micro-structured devices in range of micro meter have been manufactured based on polymer/carbon nanotubes composites by using hot embossing replication process. Firstly, the carbon nanotubes with different loading rate (0.1, 1 and 10 %) have been mixed with polypropylene (PP) in molten state to obtain the composite, the rheological properties of MWCNTs/PP composites with different CNT loading ratios were investigated by means of rheometer with a cone-and-plate geometry, the improvement of dispersion of the CNT particles in polypropylene matrix were observed by scanning electronic microscopy. Afterwards, the obtained composite were granulated in particles and used in hot embossing process to realize the replication of micro structured; in this step, a Al mould with micro-motif on surface obtain by machining with computer numerical control machine tools has been used. Finally, the micro-structured motifs on the mould have been successfully transferred with the details on the MWCNTs/PP substrate under the embossing pressure.

Recently microfluidic devices have emerged as a viable technology for the miniaturization of high throughput tools for analytical tasks related to structural biology such as screening of crystallization conditions and structural analysis. This work reports the manufacture of microfluidic chips in transparent thermoplastic polymers [poly(methylmethacrylate) (PMMA), and cyclic olefin copolymer (COC)] using two complementary technologies, injection moulding for the fabrication of the fluidic level and laser transmission welding for the sealing of the cover. A steel mould insert was produced by laser micro caving using a solid state laser radiation source (Nd:YAG, wavelength 1,064 nm). Fluidic chips of ~670 μm thickness comprising channels of 50 μm depth and width down to 50 μm were injection moulded in PMMA and COC. Joining of transparent thin cover film to the micro-injected fluidic level was performed by laser transmission welding using high power diode laser radiation (wavelength 940 nm) and an intermediate thin absorbing layer with a thickness of about several nanometers.

There is an increased need for low cost actuation technologies at the micro and nanoscale. Magnetically responsive polymer-based materials are good candidates for numerous applications in microsystems for actuation and sensing purposes. In this work, we report on nano-polymer composite magnetic silicone-based membranes, which provide the low elastic modulus needed for magnetic actuation to be effective at small scales. Passivated crystalline cobalt (~37 nm) and water based iron/cobalt (~100 nm) nanoparticles (NPs) have been synthesized using a chemical route at 50 °C and at room temperature, respectively. The NPs were characterized by Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, Atomic Force Microscopy and Vibrating Sample Magnetometry (VSM). The NPs are then uniformly dispersed in a polydimethyl siloxane (PDMS) polymer matrix in order to fabricate smooth and flexible magnetic composite membranes. The magnetic properties of the membranes for different amounts of cobalt and iron NPs (16 and 25 wt%) were characterized by VSM and deflection measurements. Co/Fe PDMS composite membranes of about 50 mm diameter and ~250 μm thickness were used under the application of ~400 Oe magnetic fields. The cobalt-PDMS membrane shows the largest deflection (~900 vs. ~80 μm for an iron-PDMS membrane). The deflections observed on these membranes are found to have a linear dependence on the applied magnetic field.

This paper presents a microfluidic device addressing the field of ambulant diagnostics in rural areas. Often, the diagnostic approach of micro-channel based point of care devices (PoCD) will target a certain marker - if e.g. on site another marker is to be checked against, the visiting doctor needs to use another test device. With the number of markers growing on a steady basis this will incur the need to transport a large number of individual test strips/cartridges, making the PoCD concept useless for this specific setting. The basis of the proposed novel device is a hybrid system combining the advantages of conventional channel-based fluidics with those of digitally controlled droplet-based fluidics. This hybrid concept uses a micro-channel based delivery partition for stored reagents with a disposable reaction partition based on electrowetting-on-dielectric to run the actual test protocol. It promises to realize a low cost approach for a Point-of-Care system with easy deployability. Conceptual implementation was done by roll embossing for the microchannels and direct structuring of the electrode elements for the EWOD substrate. The latter was laminated with a PTFE-film or coated with a nanoparticle loaded lacquer for hydrophobization. A variety of reagents were handled using a two-phase containment on the EWOD substrate, overcoming the issues associated with low surface energy fluids.

With fast development of microfluidic systems, micro-mixing becomes a very important issue. Various attempts have been made to develop passive and active micromixers, wherein the mixing efficiency is mainly dependent on the diffusion coefficient and diffusion mechanism. This paper reports modeling and fabrication of a 3D micromixer based on the principle of sequential lamination for efficient mixing. Simulation of the square tube geometry with varying inlet velocity was performed. The improvement in the mixing efficiency is attributed to the increase in the contact surface between the different fluids decreasing the diffusion path in order to improve the molecular diffusion. The design approach in the present case is also supported by analytical treatment which indicates superiority of 2D transverse flows while designing a micromixer. The optimized parameters from CFD simulation were used for fabrication of the micromixer by standard photolithographic and soft lithographic techniques.

This paper contributes selected examples based on the research and development of sub–micrometric and nanoscale structures at FEMTO–ST. In particular, exploitation of bandgap materials such as lithium niobate is a specialty of the institute and is applied in active photonic and phononic devices. Another area of active research concerns instrumentation at the microscale and nanoscale. More recently, biomolecular engineering and nanobiocharacterisation have been developed for nanobiotechnology and biosensors.

Microfluidics on foil is gaining momentum due to a number of advantages of employing thin films combined with the capability of cost-effective high-volume manufacturing of devices. In this work, ultra-thin, flexible Y-microreactors with microchannels of 100 μm width and 30 μm depth were fabricated in thermoplastic polymer foils. The fluidic pattern was hot roll embossed in 125 μm thick poly-methyl-methacrylate (PMMA) and 130 μm thick cyclic-olefin-copolymer (COC) films using a dry-etched microstructured silicon wafer as a flat embossing tool in a laminator. The sealing of the channels was performed with two different techniques, one based on lamination of SU8 dry film resist (DFR) and the other one based on spin-coated poly-dimethylsiloxane (PDMS). Testing of the interconnected microreactor was carried out using two dye colorant solutions to demonstrate mixing.

Rapid, flexible and low-cost tooling is particularly required in replication processes especially with small and medium volume as in research labs or startups. Epoxy stamps have been used in hot embossing and injection moulding since a few years. In this work, SU-8 epoxy-based patterns were generated on silicon wafers, which were employed as stamps in hot roll embossing of cyclic-olefin-copolymer and poly-methyl-methacrylate foils using a commercial laminator. This method combines the accuracy of lithographic patterning of SU-8 resist with the mass production capability of roll embossing. The stamp fabrication process can be performed in less than a few hours using photolithography for ten to hundred micrometers feature size and electron beam lithography for the sub-micronic range.

A hybrid microfluidic-EWOD (electro-wetting on dielectrics) system has been developed to meet the demand of fast detection and analysis tools in the field of ambulant diagnostics. The microfluidic device generates discrete droplets at the exit of a micropipette in which the EWOD system coordinates the motions of discrete droplets using a planar array of electrodes. In this work, a dispenser microfluidic system based on a two level microfluidic system was designed and fabricated in silicon using clean room technology then replicated in poly-dimethylsiloxane (PDMS) and cyclic olefin copolymer (COC). This system improves the mechanism of breakup of droplet due to modification of hydraulic diameter.

The present work focuses on developing cost-efficient, fast and precise tooling for prototyping and small-series manufacture of polymer chips using injection moulding. Exchangeable mould inserts were manufactured on thick silicon wafers patterned using SU-8 negative epoxy-based resist. First masters with feature size from a few tens to hundreds of micrometers were produced in SU-8 photoresist by contact photolithography. Polypropylene (PP), cyclo-olefin-co-polymer (COC) and polymethylmethacrylate (PMMA) were used as the injection moulding materials. A study of the PP parts was carried out using scanning mechanical microscopy (SMM) and scanning electron microscopy (SEM). In addition, submicronic features (500 nm) were replicated in PP from a tool patterned by e-beam lithography.

This paper presents the adaptation of a conventional injection moulding process to manufacture microfluidic components in thermoplastic polymers using alternative, exchangeable microstructured silicon-based mould inserts. The mould inserts consist of thick silicon wafers with microfeatures patterned in SU-8 epoxy photo-resist. This process allows changing the mould inserts according to the design, very easily and cost-effectively. The SU-8/Si mould inserts were robust enough to manufacture small series for laboratory purpose. More than a hundred replicas in thin polypropylene (PP) were produced successfully for a biochip designed for protein crystallisation and analysis.

A 3 : 1 composition of functional monomer (FM) multifunctional acrylate was spin-coated and later crosslinked under the influence of oxygen plasma on the surface of poly(dimethyl siloxane) (PDMS) to generate a surface-anchored crosslinked network bearing functional moieties. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and wetting angle measurements were used to analyze the crosslinked monomer surfaces. Scanning electron microscopy was used to visualize the surface of the film after modification. The results of the surface reconstruction of the FM surfaces and plasma-treated PDMS reveal that long-term hydrophilic surfaces were achieved. Thus, the surface architecture could be favorably manipulated with this remarkable technique with a suitable combination of FMs and crosslinkers. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1426-1430, 2011

Hot roll embossing is a promising technique for manufacturing and patterning of micron and sub-micron features. It attracted attention due to its high volume production and large area processing. In this work, we describe a hot-roll-embossing process for manufacturing flexible devices in different commercially available thermoplastic polymer foils using a microstructured silicon wafer as a flat stamping tool. Larger features of a 100 μm width were defined by photolithography and dry etching. A process combining deep reactive ion etching and reactive ion etching of silicon in fluorinated plasma was developed to achieve patterns in silicon with slightly positively tapered sidewalls to allow for easy demoulding. 100 μm features were successfully replicated in cyclic-olefin-copolymer (COC) and poly-methyl-methacrylate (PMMA), using relatively low temperature and multiple passes. Smaller features with 1 μm width were patterned by electron beam lithography and transferred by DRIE in silicon stamps, then replicated in COC foils.

There is need for less expensive and rapid tooling for prototyping microfluidic components and systems in thermoplastics using microreplication technique such as microinjection moulding. This paper presents the adaptation of a conventional injection moulding process using a silicon mould insert. A dry-etched silicon mould insert with aspect ratio of 4 was produced by a two-step dry etching process. Cycloolefin copolymer (COC 5013 and 8007) fluidic chips of 560 mu m thickness comprising channels of 100 pm depth and width down to 25 pm were manufactured. The injection processing temperature and mould temperature were varied from 265 degrees C to 305 degrees C and 40 degrees C to 190 degrees C respectively to study their effect on the COC replicas.

Microreactor technology is a new concept of chemical synthesis for nanoparticle production. The "state of the art" in microreactor fabrication and its application to the synthesis of nanoparticles is reviewed. The microfluidic concepts, the materials and technologies for microreactor manufacture, with particular emphasis on polymers and microreplication techniques, and their application to the synthesis of various nanomaterials in microreactors are presented. The unique synthesis properties of various nanoparticles using a microfluidic process as well as broader impact in term of nanomaterials engineering, i.e., selectivity and monodispersity, reduced amount of chemicals, fast reaction, minimum cost, a better control of the process, minimum waste and reduced amounts of reaction byproducts and improved safety, are discussed in comparison with the traditional wet-chemical batch synthesis approach.

Soft lithography and self-assembly provide powerful means of organizing colloidal solution of synthesized nanoparticles (NPs) for a wide variety of application. Pattern transfer of silicon dioxide (SiO2) nanoparticles–polymethylmethacylate (PMMA) nanocomposite was investigated using two such soft lithographic techniques, micro molding in capillaries (MIMIC) and micro transfer molding (μTM) using an elastomeric stamp in Polydimethyl siloxane (PDMS). Nanocomposite periodic arrays of 20μm wide and 10μm deep lines with 10μm spacing were obtained over approximately 1cm2 area on silicon substrates by μTM and MIMIC using a 3wt.% monodisperse silica nanoparticles (∼338±2nm) in polymethyl methacrylate (PMMA) solution. In addition, free standing nanocomposite self-standing films of centimeter size were also manufactured by μTM. Single line of nanocomposite could also be obtained using MIMIC with a lower concentration of silica NPs (0.25wt.%) in PMMA.

Two dry subtractive techniques for the fabrication of microchannels in borosilicate glass were investigated, plasma etching and laser ablation. Inductively coupled plasma reactive ion etching was carried out in a fluorine plasma (C4F8/O2) using an electroplated Ni mask. Depth up to 100 μm with a profile angle of 83°–88° and a smooth bottom of the etched structure (Ra below 3 nm) were achieved at an etch rate of 0.9 μm/min. An ultrashort pulse Ti:sapphire laser operating at the wavelength of 800 nm and 5 kHz repetition rate was used for micromachining. Channels of 100 μm width and 140 μm height with a profile angle of 80–85° were obtained in 3 min using an average power of 160 mW and a pulse duration of 120 fs. A novel process for glass–glass anodic bonding using a conductive interlayer of Si/Al/Si has been developed to seal microfluidic components with good optical transparency using a relatively low temperature (350°C).