shipped · 2023-10 → 2024-01
Microfluidics droplet reactor
A droplet-based lab-on-a-chip with a four-channel Arduino-controlled peristaltic pump system. Designed to bring accessible microfluidics into educational labs without a cleanroom.
Project highlights
- Cleanroom-free fabrication: resin 3D-printed master + PDMS casting at home-lab temperatures.
- Self-developed peristaltic pump system at ~$48 per channel, Arduino-controlled.
- Digital microscopy + Python/OpenCV for real-time droplet tracking.
- Co-authored publication based on the work.
Technical specs
- Channel dimensions: 300 μm
- Flow rate: 40–160 ml/min
- Droplet size: 50–150 μm
- Channel flow speed: 0.5–2 mm/s
Manufacturing process
The chip is fabricated from PDMS cast over a 3D-printed master. We used an Anycubic Photon 2 LCD resin printer — accuracy down to ~50 μm in every axis, repeatable, and a fraction of the cost of a photolithography setup. The full pipeline: print the master → wash in isopropanol → post-cure → rest 24 hours → cast PDMS → activate and bond.
The PDMS is Silagerm 8040, a two-component silicone, cured at a reduced 50 °C. The temperature matters: at the standard ~80 °C, the resin master warps and the channel geometry drifts. Lower-temperature casting trades a longer cure for a master you can reuse cleanly. After bonding, inlets and outlets are surface-activated and tubed.
Peristaltic pump system
A traditional syringe pump runs hundreds of dollars per channel. Mine is a four-channel peristaltic pump in a custom 3D-printed enclosure, with Arduino PWM driving each motor. Flow rates are calibrated against the inlet profile the chip needs, and the four channels stay synchronised so the dispersed and continuous phases enter in the right ratio.
Total cost per pump unit, all components included, is about $48 — less than half a syringe pump and comfortably within an educational budget. The cost lever is what unlocks the rest: with a $300-ish resin printer plus ~$48 per pump channel, the entire reactor stops being "lab equipment" and starts being something a school can actually build.
Results & analysis
Droplets are tracked in real time off a digital microscopy feed using a Python + OpenCV pipeline. The system extracts droplet boundaries frame by frame, tags each one through its trajectory, and outputs both speed and size distributions per run.
Across the full operating envelope, droplet velocity scales near-linearly with inlet flow rate, and the size distribution sits comfortably inside the 50–150 μm target. The reactor produces stable, characterisable droplets across all four channels at the speeds the educational use-case needs.
Process demonstration
Real-time microscopy of droplets forming in the chip. Loops below.
Educational impact
The whole point of the project. PDMS lab-on-a-chip work is normally locked behind a cleanroom and a five-figure equipment bill. With the design here, a teacher with a resin printer, an Arduino, and roughly $48 of parts per pump channel can run real droplet experiments with their students. The procedure is reproducible from off-the-shelf components, end to end, and the digital-microscopy + computer-vision layer makes the analysis quantitative without requiring expensive proprietary software.
The full method is documented in the publication linked below. The system is also flexible enough to be adapted — different channel geometries, different fluids, different droplet-size targets — using the same fabrication pipeline.