Mathieu Hautefeuille

Utilization of a digital-versatile-disc pickup head for benchtop laser microfabrication

Laser microfabrication is now offering interesting solutions to rapidly produce high-resolution photomasks or microstructures. However, most works require expensive commercial lasers and computer numerical control platforms, limiting its use by a large public. In this paper, we report the construction of a simple, custom-made, easily reproducible, automated laser system, based on a DVD optical pickup head. A user-friendly computer interface specifically designed to operate a motorized three-axis platform with micrometric precision controls focus distance and in-plane displacements. Writing performance characterization for both direct ablation and sintering of commercial black toner demonstrated flexibility in tridimensional microfabrication resolution and speed thanks to precise management of laser power and exposure time, with a minimal resolution of 3.1 μm.

Rapid fabrication of on-demand high-resolution optical masks with a CD-DVD pickup unit

A low-cost, direct fabrication technique with a micrometer range resolution has been implemented for rapid prototyping of optical masks for photolithography and structured light and diffraction optics applications. Using a setup based on the optical unit of a compact disc-digital versatile disc burner, a low-energy infrared laser beam was focused on a thin polymeric layer with embedded absorbing carbon nanopowder coated on a transparent glass substrate. This allowed for the generation of a custom-made transparent pattern in a computer numerical control fashion. In addition to its great simplicity and repeatability, the method also enables grayscale contrasts for each pixel individually, and fabricated masks proved to resist high intensities.

Laser induced deformation in polydimethylsiloxane membranes with embedded carbon nanopowder

We demonstrate optically induced micron-range deformation of polydimethylsiloxane (PDMS) membranes with embedded carbon nanopowder. The mechanical deformation can be controlled by low power laser irradiation of the samples and the resulting surface modifications are analyzed via dynamic speckle measurements. Photothermal effects due to optical absorption by the nanopowder are shown to deform the polymer samples leading to localized mechanical stresses induced via thermal expansion of the PDMS.

Photothermal Effects and Applications of Polydimethylsiloxane Membranes with Carbon Nanoparticles

The advent of nanotechnology has triggered novel developments and applications for polymer-based membranes with embedded or coated nanoparticles. As an example, interaction of laser radiation with metallic and carbon nanoparticles has shown to provide optically triggered responses in otherwise transparent media. Incorporation of these materials inside polymers has led to generation of plasmonic and photothermal effects through the enhanced optical absorption of these polymer composites. In this work, we focus on the photothermal effects produced in polydimethylsiloxane (PDMS) membranes with embedded carbon nanoparticles via light absorption. Relevant physical parameters of these composites, such as nanoparticle concentration, density, geometry and dimensions, are used to analyze the photothermal features of the membranes. In particular, we analyze the heat generation and conduction in the membranes, showing that different effects can be achieved and controlled depending on the physical and thermal properties of the composite material. Several novel applications of these light responsive membranes are also demonstrated, including low-power laser-assisted micro-patterning and optomechanical deformation. Furthermore, we show that these polymer-nanoparticle composites can also be used as coatings in photonic and microfluidic applications, thereby offering an attractive platform for developing light-activated photonic and optofluidic devices.

Low-cost formation of bulk and localized polymer-derived carbon nanodomains from polydimethylsiloxane

Summary We present two simple alternative methods to form polymer-derived carbon nanodomains in a controlled fashion and at low cost, using custom-made chemical vapour deposition and selective laser ablation with a commercial CD-DVD platform. Both processes presented shiny and dark residual materials after the polymer combustion and according to micro-Raman spectroscopy of the domains, graphitic nanocrystals and carbon nanotubes have successfully been produced by the combustion of polydimethylsiloxane layers. The fabrication processes and characterization of the byproduct materials are reported. We demonstrate that CVD led to bulk production of graphitic nanocrystals and single-walled carbon nanotubes while direct laser ablation may be employed for the formation of localized fluorescent nanodots. In the latter case, graphitic nanodomains and multi-wall carbon nanotubes are left inside microchannels and preliminary results seem to indicate that laser ablation could offer a tuning control of the nature and optical properties of the nanodomains that are left inside micropatterns with on-demand geometries. These low-cost methods look particularly promising for the formation of carbon nanoresidues with controlled properties and in applications where high integration is desired.

Use of a CD laser pickup head to fabricate microelectrodes in polymethylmethacrylate substrates for biosensing applications

In this work, we report a simple fabrication method for microelectrodes on a polymethylmethacrylate substrate, using a low-cost laser platform based on a CD-DVD unit for direct rapid-prototyping. We used this laser microfabrication technique to etch any desired design on polymethylmethacrylate substrates to produce microchannels with controlled geometry, with a highly repeatable micron-scale resolution. Those shallow microchannels were then filled with a conductive paste of material of our choice that was converted into microelectrodes of desired shapes and geometries after drying. To validate our process, different geometries, sizes and materials were used as electrodes, and then tested for amperometry and impedance measurements. Development of these microelectrodes is motivated by their potential application in sensors and biosensors, such as glucose and cell counting, as demonstrated in this paper.

Fabrication of large all-PDMS micropatterned waveguides for lab on chip integration using a rapid prototyping technique

A simple method for manufacturing centimeter-long all-PDMS embedded and rib microwaveguides is presented. It allows for the fabrication of centimeter-long micromolds by direct laser ablation of a desired waveguide pattern inside an acrylic sheet to create a pattern which is then transferred to a poly-dimethylsiloxane (PDMS) layer using soft-lithography. A refractive index difference between the core and cladding of 1.3x10−3 was achieved by controlling the PDMS curing and linear attenuation of 1.27 dB/cm for embedded and 2.36 dB/cm for a rib waveguide, similar to other techniques. Finally, a beamsplitter was fabricated to demonstrate that our low-cost process is suitable to integrate waveguide devices on lab on chip platforms.

Fabrication of low-cost micropatterned polydimethyl-siloxane scaffolds to organise cells in a variety of two-dimensioanl biomimetic arrangements for lab-on-chip culture platforms

We present the rapid-prototyping of type I collagen micropatterns on poly-dimethylsiloxane substrates for the biomimetic confinement of cells using the combination of a surface oxidation treatment and 3-aminopropyl triethoxysilane silanisation followed by glutaraldehyde crosslinking. The aim of surface treatment is to stabilise microcontact printing transfer of this natural extracellular matrix protein that usually wears out easily from poly-dimethylsiloxane, which is not suitable for biomimetic cell culture platforms and lab-on-chip applications. A low-cost CD-DVD laser was used to etch biomimetic micropatterns into acrylic sheets that were in turn replicated to poly-dimethylsiloxane slabs with the desired features. These stamps were finally inked with type I collagen for microcontact printing transfer on the culture substrates in a simple manner. Human hepatoma cells (HepG2) and rat primary hepatocytes, which do not adhere to bare poly-dimethylsiloxane, were successfully seeded and showed optimal adhesion and survival on simple protein micropatterns with a hepatic cord geometry in order to validate our technique. HepG2 cells also proliferated on the stamps. Soft and stiff poly-dimethylsiloxane layers were also tested to demonstrate that our cost-effective process is compatible with biomimetic organ-on-chip technology integrating tunable stiffness with a potential application to drug testing probes development where such cells are commonly used.

Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer

We have constructed a counterpropagating optical tweezers setup embedded in a Sagnac interferometer in order to increase the sensitivity of position tracking for particles in the geometrical optics regime. Enhanced position determination using a Sagnac interferometer has previously been described theoretically by Taylor et al. [Journal of Optics 13, 044014 (2011)] for Rayleigh-regime particles trapped in an antinode of a standing wave. We have extended their theory to a case of arbitrarily-sized particles trapped with orthogonally-polarized counter-propagating beams. The working distance of the setup was sufficiently long to optically induce particle oscillations orthogonally to the axis of the tweezers with an auxiliary laser beam. Using these oscillations as a reference, we have experimentally shown that Sagnac-enhanced back focal plane interferometry is capable of providing an improvement of more than 5 times in the signal-to-background ratio, corresponding to a more than 30-fold improvement of the signal-to-noise ratio. The experimental results obtained are consistent with our theoretical predictions. In the experimental setup, we used a method of optical levitator-assisted liquid droplet delivery in air based on commercial inkjet technology, with a novel method to precisely control the size of droplets.

Development of a wearable for oximetry and patient physical activity correlation

In this work we show preliminary advance in the development of a low-cost wrist wearable that measures levels of oxygen saturation levels in blood (SpO2) and physical activity simultaneously. For the monitoring of SpO2, we use pulse oximetry (a non invasive technique) by backscattering detection at the wrist. The device consists in an optoelectronics layer based on two light-emitting diodes (650nm and 960 nm) and a photodiode, a 3-axis gyroscope, a 3-axis accelerometer and a microcontroller capable of data processing and data transmission via bluetooth. In addition to, our sensor allows to save data for later analysis.