A Laser-Micromachined PCB Electrolytic Micropump Using an Oil-Based Electrolyte Separation Barrier

We report a laser-micromachined electrolytic PCB micropump with an oil separation barrier. As advances in terms of miniaturization and performance from our previous mesoscale PCB electrolytic pump (Kim et al. in Sens Actuators A Phys 277:73-84, 2018), we employed a simple yet rapid tape-based laser-machining technique called tape-liner-supported plastic laser micromachining and pattern transfer to fabricate a microfluidic coverslip for a PCB electrode chip. Using our microfabrication technique, the coverslip is bonded to a PCB chip to form an enclosed microscale pump with a high machining precision and no need for alignment of intermediate adhesive tapes with structural layers as commonly done in previous tape-bonding work. The completed micropump demonstrated excellent pumping performance: flow rate up to 24.49 ml/min and backpressure up to 394 kPa. Electrochemical activation of electrodes consisting of a train of voltage pulses and sweeps improves the pumping performance. In order to prevent unwanted interspersion between the electrolyte and working fluid, various separation diaphragms were previously employed, but at the cost of limited working volume and flow rate as the diaphragms were permanently anchored to the pump body. Here we propose to use an oil plug as an untethered (mobile) separation barrier. After a systematic study of properties of common oils, we tested fluorinated oil (HFE-7500), hexadecane, and tetradecane as the candidate barrier materials. HFE-7500 was chosen because its interface was stable and did not degrade pumping performance for the flow-rate range of 8.47 mu l/min-2.48 ml/min. We expect our micropump with the oil plug to be used as an excellent pressure source for integrated lab-on-a-chip devices, especially lab-on-a-PCBs.