Microfluidic devices obtained by thermal toner transferring on glass substrate

Abstract

A new process for the manufacture of microfluidic devices based on deposition of laser-printing toner on glass substrates is described. It is an alternative method to the toner on polyester film (toner-polyester) one, previously introduced. Commercial laser printers cannot print directly on glass, thus the toner must first be printed on a special paper and then transferred by heating under pressure to the glass surface. Although this procedure is more complex than the toner-polyester one, it can be repeated several times, yielding multiple toner layers. Even without special alignment equipment, up to four layers could be satisfactorily piled up. Characterization tests revealed that the toner-glass devices have similar behavior as toner-polyester ones regarding the toner layer porosity. The main advantages of the toner-glass technology are improved mechanical stability, possibility of multiple toner layers, augmented electroosmotic flow (EOF), and improved heat transfer. On the other hand, toner adhesion to glass is weaker than to polyester, which limits the device lifetime and usable liquid media. The measured EOF mobility (3.5 x 10(-4) cm2.V(-1).s(-1) for pH 7) suggests that it is mainly determined by the glass surface, being little influenced by the toner walls. Microchip electrophoresis with contactless conductivity detection and photometric detection were implemented using toner-glass devices.

Visible LED-Based Instrumentation for Photometric Determination of Electroosmotic Flow in Microchannels

“…The mobility of the EOF obtained for this glass/toner microchip was (5.75 ± 0.01) 10 -4 cm 2 V -1 s -1 , measured with solutions of patent blue V at pH 7.0 and using the described conditions. This value is higher than 3.5 10 -4 cm 2 V -1 s -1 obtained in a previous work, 22 but one must consider differences in the experimental conditions, such as ionic strength and temperature. Most important, the order of magnitude of the measured EOF is in agreement to glass/toner surfaces.…”

“…Most important, the order of magnitude of the measured EOF is in agreement to glass/toner surfaces. 22 The EOF measurement obtained simultaneously using the current method was (4.2 ± 0.1) 10 -4 cm 2 V -1 s -1 . The difference could be attributed to small variations in the position of the photometric detector and difficulties in determine the exact t eo in the current versus time graph.…”

“…Glass/ toner microchips were produced according to fabrication technology described by Do Lago et al 22 PDMS microchips were fabricated using the well-established soft-lithographic protocol, where a master is produced and microchannels are replicated via direct polymerization over the master. 23 The high-relief master was fabricated in the Laboratory of Microfabrication at the National Synchrotron Light Source (LNLS, Campinas, SP, Brazil) using standard photolithographic protocols.…”

“…A monolithic photodiode and amplifier OPT101 (Texas Instruments, Dallas, TX, USA) as well as the electronic circuitry (Supplementary Information) were cased in a plastic box and the ensemble was adapted to the microscope using a copper tube. 22 The output of the amplifier was interfaced to a Pentium 133 MHz microcomputer through a PCL-711 interface card (Advantech, Taipei, Taiwan). The data acquisition program was written in Delphi 5.0 (Borland).…”

Shrinky-Dink microfluidics: rapid generation of deep and rounded patterns

“…Such shallow channels are adequate for many microfluidic applications but not amenable for use with large mammalian cells (.10 mm in diameter) as well as other applications, such as flowing chemotactic gradients across adherent cells in a channel with minimal shearing. 5 While Lago et al 6 introduced a way to circumvent the height limitation of single-layer ink by printing up to four times using a thermal toner transfer method onto a glass substrate, the maximum height obtained with this approach was 25 mm. Vullev et al 7 demonstrated a non-lithographic fabrication approach of microfluidic devices by printing positive-relief masters with a laser-jet printer for detecting bacterial spores; the height of the channels, which is likewise dependent on the height of the ink, is limited to between 5 and 9 mm.…”