Design and implementation of injector/distributor structures for microfabricated non-porous pillar columns for capillary electrochromatography

A previously proposed foil definition is applied in the design of injector/distributor structures for solid microfabricated column structures for capillary electrochromatography. In addition to a typical bifurcated distributor, an optimized design alternative with two different configurations is experimentally evaluated. Optimized designs yielded a flat profile for the injected sample with a maximum of 3% variation from the mean width, while it went up to 18% for the typical bifurcated distributor. The implemented electrokinetic injection approach enabled controlling the volume of the injected sample accurately without sacrificing the compactness of the device design. The width of the injected sample was directly proportional to the injection time, namely 165 and 218 μm base widths were obtained for 0.6 and 0.8 s of feeding, respectively. Reducing the external porosity of the distributor by 85% compared to the typical design, optimized distributors caused a decrease in the mean flow velocity of up to 70%. However, having a flat initial plug shape enabled the separation of a mixture of Coumarin 440, 460, 480 and 540 at 1 mm downstream of the injection point in 80 s, while it was even not possible to detect the C440 signal for a typical bifurcated design

The development of titanium silicide - boron doped polysilicon resistive temperature sensors

Thin films of titanium silicide $(TiSi_2$) formed on heavily boron-doped polycrystalline silicon $(poly-Si/B^+)$ were applied for the first time for resistive temperature sensing. The temperature sensors exhibited a high-temperature coefficient of resistance of 3.8 x 10^{-3}^{\circ}\mathrm{C}^{-1}, a linear dependence of resistance on temperature and an excellent thermal and electrical stability up to 800 $^{\circ}\mathrm{C}$. This work discusses the fabrication method and the morphological and electrical characterization of the $TiSi_2/poly-Si$ thin film resistors throughout the stages of its formation

Multi-walled microchannels: free-standing porous silicon membranes for use in µTAS

Electrochemically formed porous silicon (PS) can be released from the bulk silicon substrate by underetching at increased current density. Using this technique, two types of channels containing free-standing layers of PS were constructed, which were failed multi-walled microchannels (MW µCs). They can be used in devices like microsieves, microbatteries, and porous electrodes. Two types of MWµC were made: the 'conventional' version, consisting of two or more coaxially constructed microchannels separated by a suspended PS membrane, and the buried variety, where a PS membrane is suspended halfway in an etched cavity surrounded by silicon nitride walls. The latter is more robust. The pore size of the PS was measured using transmission electron microscopy and field emission gun scanning electron microscopy (FEGSEM) and found to be of the order of 7 n

Multichannel quench-flow microreactor chip for parallel reaction monitoring

This paper describes a multichannel silicon-glass microreactor which has been utilized to investigate the kinetics of a Knoevenagel condensation reaction under different reaction conditions. The reaction is performed on the chip in four parallel channels under identical conditions but with different residence times. A special topology of the reaction coils overcomes the common problem arising from the difference in pressure drop of parallel channels having different length. The parallelization of reaction coils combined with chemical quenching at specific locations results in a considerable reduction in experimental effort and cost. The system was tested and showed good reproducibility in flow properties and reaction kinetic data generation

Synchronized, continuous-flow zone electrophoresis

A new method for performing continuous electrophoretic separation of complex mixtures in microscale devices is proposed. Unlike in free-flow electrophoresis devices, no mechanical pumping is requiredboth fluid transport and separation are driven electrokinetically. This gives the method great potential for on-a-chip integration in multistep analytical systems. The method enables us to collect fractionated sample and tensfold purification is possible. The model of the operation is presented and a detailed description of the optimal conditions for performing purification is given. The chip devices with 10-μm-deep separation chamber of 1.5 mm × 4 mm in size were fabricated in glass. A standard microchip electrophoresis setup was used. Continuous separation of rhodamine B, rhodamine 6G, and fluorescein was accomplished. Purification was demonstrated on a mixture containing rhodamine B and fluorescein, and the recovery of both fractions was achieved. The results show the feasibility of the method

Silicon-based microreactors as research tools in chemistry

In this contribution suitability of silicon-technology based microreactors for performing research on reactions where temperature control is essential is discussed. The versatility of silicon micromachining technology is elucidated by describing the fabrication and performance of two types of microreactors for studying Rh-catalyzed gas phase reactions. Depending on the design of the microreactor, working temperatures up to 800 degrees C can be obtaine

Planar Nanoneedles on-chip for intracellular measurements

We present for the first time a functional planar SiN-nanoneedle system for intracellular mass transport and in vivo electrophysiological measurements on-chip. Though several micro- or nanoneedles for cell research have been described in literature, no needles of this small size equipped with nanosized inner channels or electrodes have been reported. A propidium iodide assay verifies the excellent penetration performance of the nanoneedles with diminished leakage from the cell after insertion and release of the needle from HL60- cells. Hollow needles connected to on-chip sub-picoliter electrochemical dosing systems are in development