Fully chip-embedded automation of a multi-step lab-on-a-chip process using a modularized timer circuit

Abstract

For highly-integrated microfluidic systems, an actuation system is necessary to control the flow; however, the bulk of actuation devices including pumps or valves has impeded the broad application of integrated microfluidic systems. Here, we suggest a microfluidic process control method based on built-in microfluidic circuits. The circuit is composed of a fluidic timer circuit and a pneumatic logic circuit. The fluidic timer circuit is a serial connection of modularized timer units, which sequentially pass high pressure to the pneumatic logic circuit. The pneumatic logic circuit is a NOR gate array designed to control the liquid-controlling process. By using the timer circuit as a built-in signal generator, multi-step processes could be done totally inside the microchip without any external controller. The timer circuit uses only two valves per unit, and the number of process steps can be extended without limitation by adding timer units. As a demonstration, an automation chip has been designed for a six-step droplet treatment, which entails 1) loading, 2) separation, 3) reagent injection, 4) incubation, 5) clearing and 6) unloading. Each process was successfully performed for a pre-defined step-time without any external control device.

Autonomous microfluidic actuators for periodic sequential flow generation

“…In comparison, the operation process of our system is much simpler and has higher scalability. Furthermore, a fluidic timer circuit used a constant pneumatic pressure input and implemented six-step sequential flows ( 27 ), but it did not show sophisticated periodic flows that we presented with the orchestration of AA and MAs. Because of its requirement of comparatively high-pressure input, the timer circuit cannot be periodically triggered by the AA that we developed.…”

“…In our previous studies, we implemented fluidic switching without external controllers, but the switching was limited to only two solution flows (24)(25)(26). Recently, a fluidic timer circuit presented a six-step sequential flow, but its initiation was manually triggered without periodic operation (27). Therefore, a different approach that can truly implement sequential periodic flows is strongly required for the practical applications without any user instructions and external dynamic controllers.…”