PolyJet Three-dimensional-Printed Microchip Devices With Integrated Carbon Electrodes for Neurotransmitter Analysis

We present an approach for integrating carbon ink electrodes into PolyJet three-dimensional (3D)-printed microfluidic devices for electrochemical (EC) detection. Devices for both microchip-based electrophoresis (ME) and microchip-based flow injection analysis can be created with this methodology. The fabrication involves printing two separate components, a channel layer and an electrode layer, which are thermally bonded to form the final device. For the electrode layer, carbon electrodes are first patterned onto glass substrates using a micromolding technique. A custom stencil is printed directly onto the PolyJet tray to guide precise alignment; the electrode layer is then printed directly over the glass substrate, transferring and embedding the electrodes accurately within the 3D-printed structure. The channel layer is produced by 3D printing either onto a pre-fabricated mold featuring a T-intersection (for ME) or onto the printer tray along with solid support (for microchip-based flow injection analysis). This method yields devices with reliable electrode-channel alignment and minimal band broadening. For ME experiments, the device effectively separated a mixture of neurotransmitters with theoretical plate counts up to 136 000 plates/m and a limit of detection for dopamine of 170 nM. Additionally, we demonstrate how to use 3D printing to integrate off-chip processes such as microdialysis sampling with ME and EC detection. Lastly, we show how microchip flow-based injection analysis devices featuring single or dual in-channel carbon electrodes can also be produced with this approach.