A step towards fully automated 3D printed instruments

In the past few decades, significant advancement has been made towards the development of automated microfluidic platforms because of their unique advantages such as integration of different functions, minimum consumption of samples/reagents, low cost, and quick sample analysis. Various components of an instrument e.g. detectors, flow cell, pumps etc., are usually customised in order to improve instrument performance in terms of analysis time, liquid sample and reagents consumption, and reliability through automation. 3D printing, a rapidly growing manufacturing technique, is an attractive alternative to traditional manufacturing techniques (e.g. subtractive manufacturing) because of its ability to print almost any structure on demand with minimal time and cost. The focus of this study was to fabricate and characterise key components of the microfluidic systems including detectors, flow cell, and pumps, and potentially integrate them to produce automated analytical instrument for application in microfluidics. First, this study explored the potential of a commonly available low cost FDM 3D printer to manufacture a photometric detector body consisting of integrated slit and hollow structures, to position a LED and photodiode, on either side of capillary tubing (Chapter 2). The spatial orientation for printing was investigated to facilitate the printing of a narrow size slit suitable for capillaries and tubing (i.d. 50 ˜í¬¿m to 10 mm). A slit of 70 ˜í¬¿m was printed when the slit was positioned in the XY plane in parallel with the print direction. The detection body with integrated slit showed satisfactory performance for both large diameter tubing and narrow capillaries. The performance of the 3D printed housing with a 70 ˜í¬¿m slit was compared with a commercial CE interface for the CE separation of Zn\\(^{2+}\\) and Cu\\(^{2+}\\) complexes with PAR. The second aim of this study was to develop a flow cell with an integrated channel to avoid the need for external capillaries and tubing. Chapter 3 describes the use of multi-material 3D printing technology for the fabrication of a complex photometric detector flow cell with integrated channel and slit. Multi material 3D printing allowed the fabrication of detection window using transparent material, and channel and flow cell body using an opaque material, all printed in one piece. The flow-cell was optimised by varying the design features including slit dimension and optical path-length. The performance of the printed flow cell devices was characterised with a standard dye solution by determining the stray light %, effective path-length and the signal to noise ratio. A device consisting of 500 ˜í¬¿m slit with 10 mm optical path-length showed best performance. Third, the use of multi-material FDM 3D printing to manufacture an electroosmotic pump (EOP) with multiple functionalities was investigated as fluid pumping is a key feature of a microfluidic system and usually requires a micro pump manipulate liquid flow at a smaller scale (‚Äöv¢¬ß 1 mm). Chapter 4 presents the first use of this technology for the fabrication of an EOP with integrated electrodes in a single piece. The key component of the EOP is a multiple channel (mesh) and integrated 3D printed electrodes. The novel design feature, mesh was used to create the first asymmetrical surface-area EOP. The EOP was printed by using a non-conductive Acrylonitrile butadiene styrene (ABS) and a conducting ABS material was used for printing of the three electrodes around the pumping channel. These three electrodes were printed to provide an electrode for applying the voltage and two electrodes to ground the liquid within the EOP by decoupling the electric field in the pump channels from the other parts of the device. The newly developed EOP was characterised by calculating current, flow rate and pressure at various voltages ranging from 0.1- 0.5 kV. The satisfactory performance of the 3D printed EOP showed the potential of multi-material 3D printing as an alternative approach for the fabrication of low-cost microfluidic pumping devices. Repeatability and accuracy of the fabrication method is critical for the manufacturing of reliable devices and instruments. Chapter 5 describes the repeatability and accuracy experiments conducted to investigate the repeatability and accuracy of the printing method for the manufacturing of newly developed devices presented in this thesis.