Prototyping chips in minutes: Direct Laser Plotting (DLP) of functional microfluidic structures

We report a fast and simple prototyping method to fabricate polymer-based microfluidic chips using Direct Laser Plotting (DLP) technique, by which various functional micro-structures can be realized within minutes, in a mask-free and out-of-cleanroom fashion. A 2D Computer-Aid-Design (CAD) software was employed to layout the required micro-structures and micro-channels, a CO2 laser plotter was then used to construct the microstructures. The desired patterns can be plotted directly on PDMS substrates and bio-compatible polymer films by manipulating the strength and density of laser pulses. With the DLP technique, chip-embedded micro-electrodes, micro-mixers and 3D microfluidic chips with 5 layers, which normally require several days of work in a cleanroom facility, can be fabricated in minutes in common laboratory. This novel method can produce microfluidic channels with average feature size of 100 μm, while feature size of 50 μm or smaller is achievable by making use of the interference effect from laser impulsion. In this report, we present the optimized parameters for successful fabrication of 3D microchannels, micro-mixers and microfluidic chips for protein concentration measurements (Bovine Serum Albumine (BSA) test), and a novel procedure to pattern flexible embedding electrodes on PDMS-based microfluidic chips. DLP offers a convenient and low cost alternative to conventional microfluidic channel fabrication technique which relies on complicated and hazardous soft lithography process.