Fine tuning the roughness of powder blasted surfaces

Powder blasting (abrasive jet machining) has recently been introduced as a bulk-micromachining technique for brittle materials. The surface roughness that is created with this technique is much higher (with a value of Ra between 1¿2.5 ¿m) compared to general micromachining techniques. In this paper we study the roughness of powder blasted glass surfaces, and show how it depends on the process parameters. The roughness can also be changed after blasting by HF etching or by using a high-temperature anneal step. Roughness measurements and scanning electron microscopy images show the quantitative and qualitative changes in roughness. These post-processes will allow us to investigate the influence of surface roughness on the microsystem performance in future research

A Microfabricated 4-Electrode Conductivity Sensor with Enhanced Range

Conductivity is a routinely measured parameter to assess impurities in water. Changing the geometry from parallel plate electrodes to planar microfabricated dual-band or interdigitated electrodes, these sensors could be miniaturized. Based on this approach, we designed 2-electrode conductivity sensors and compared their performance with a commercially available device. Adding another electrode pair (either as dual-band or meandering between interdigitated electrodes), a 4-electrode sensor was formed for which the measuring range could be enhanced to 3 × 10−6⁻12 × 10−3 S/cm

Surface effects in the esterification of 9-pyrenebutyric acid within a glass micro reactor

Surface phenomena are an important contribution to the chip effect, leading to higher yields and shorter reaction times, as demonstrated for the acid-catalysed esterification of 9-pyrenebutyric acid within a glass fabricated micro reactor

Integrated microfluidic system enabling (bio)chemical reactions with on-line MALDI-TOF mass spectrometry

A continuous flow micro total analysis system (μ-TAS) consisting of an on-chip microfluidic device connected to a matrix assisted laser desorption ionization [MALDI] time-of-flight [TOF] mass spectrometer (MS) as an analytical screening system is presented. Reaction microchannels and inlet/outlet reservoirs were fabricated by powderblasting on glass wafers that were then bonded to silicon substrates. The novel lab-on-a-chip was realized by integrating the microdevice with a MALDI-TOFMS standard sample plate used as carrier to get the microfluidic device in the MALDI instrument. A novel pressure-driven pumping mechanism using the vacuum of the instrument as a driving force induces flow in the reaction microchannel in a self-activating way. Organic syntheses as well as biochemical reactions are carried out entirely inside the MALDI-MS ionization vacuum chamber and analyzed on-line by MALDI-TOFMS in real time. The effectiveness of the μ-TAS system has been successfully demonstrated with several examples of (bio)chemical reactions

A MALDI-chip integrated system with a monitoring window

The integration of a monitoring port along the microfluidic path of a MALDI-chip integrated device is described. Optimization of the microreactor design allows longer reaction and measuring times. The Schiff base reaction between 4-tert-butylaniline ( 1) and 4-tert-butylbenzaldehyde ( 2) in ethanol was carried out on-chip in the MALDI ionization chamber and the formed imine 3 was detected in real time, demonstrating the feasibility of the monitoring window approach. This preliminary result opens the way to on-chip kinetic studies by MALDI-MS, by opening multiple monitoring windows along the microchannel