Modular LEGO brick microfluidics

Abstract

Wider use and adaptation of microfluidic systems is hindered by the infrastructure, knowledge, and time required to build prototype devices, especially when multiple fluid operations and measurements are required. As a result, rapid prototyping methods based on planar and three-dimensional printing are attracting interest; however, these techniques cannot produce structures with the resolution, smoothness, and feature size needed for standard microfluidic devices. Herein I present a new approach to rapidly construct modular microfluidic systems by modification and assembly of interlocking injection-molded blocks. I demonstrate this principle using micromilling of store-bought LEGO® bricks to create surface fluidic pathways on bricks, and develop procedures for sealing and interconnecting bricks to form modular, reconfigurable microfluidic systems. Micromilling using a desktop machine achieves channel dimensions of 50 pm in depth and 150 pm in width, or greater, etched into the sidewalls of blocks. Sealing these channels with adhesive films allows internal fluid pressure of at least 400 kPa. The intrinsic tolerances of injection molded bricks and their elastically averaged connections gives mechanical locating repeatability of 1 pm, which enables fluid to pass between bricks via an O-ring with >99.9% sealing reliability. Using the LEGO-based approach, I build systems made of assembled brick units for generating droplets, sensing light, sorting with inertial and magnetic forces, and repeatably positioning a smartphone camera, and characterize their performance. Then, I fabricate and measure LEGO-like bricks made by FDM and SLA three-dimensional printing, showing that they can integrate with injection-molded bricks to add useful function, although their surface quality, resolution, and material limit performance. In addition, I adapt these components for two educational activities for high school students: a colorimetric titration device and a modular designable boat. The standard interface among all bricks enables a wide variety of brick units to be incorporated onto a common platform, making this "lab on a brick" a new and viable platform for advancing research and education in microfluidics.