A microfluidic transistor for automatic control of liquids

Abstract

Microfluidics have enabled notable advances in molecular biology1,2, synthetic chemistry3,4, diagnostics5,6 and tissue engineering7. However, there has long been a critical need in the field to manipulate fluids and suspended matter with the precision, modularity and scalability of electronic circuits8–10. Just as the electronic transistor enabled unprecedented advances in the automatic control of electricity on an electronic chip, a microfluidic analogue to the transistor could enable improvements in the automatic control of reagents, droplets and single cells on a microfluidic chip. Previous works on creating a microfluidic analogue to the electronic transistor11–13 did not replicate the transistor’s saturation behaviour, and could not achieve proportional amplification14, which is fundamental to modern circuit design15. Here we exploit the fluidic phenomenon of flow limitation16 to develop a microfluidic element capable of proportional amplification with flow–pressure characteristics completely analogous to the current–voltage characteristics of the electronic transistor. We then use this microfluidic transistor to directly translate fundamental electronic circuits into the fluidic domain, including the amplifier, regulator, level shifter, logic gate and latch. We also combine these building blocks to create more complex fluidic controllers, such as timers and clocks. Finally, we demonstrate a particle dispenser circuit that senses single suspended particles, performs signal processing and accordingly controls the movement of each particle in a deterministic fashion without electronics. By leveraging the vast repertoire of electronic circuit design, microfluidic-transistor-based circuits enable fluidic automatic controllers to manipulate liquids and single suspended particles for lab-on-a-chip platforms.

Centrifugo-Pneumatic Reciprocating Flowing Coupled with a Spatial Confinement Strategy for an Ultrafast Multiplexed Immunoassay

“…In the past few decades, numerous efforts have been made to tackle the aforementioned challenges by harnessing emerging microfluidic technology. In contrast to conventional manual operation and static incubation reactions, the microfluidic approach involves integrating traditional immune-analysis procedures onto a microchip and simplifying the process through continuous flow-based reactions. ,− Notably, the ultralow dimensions of the microfluidic platform contribute to a high surface-to-volume ratio, thereby reducing diffusion distance. − However, it is important to consider that the single-pass flow-through scheme employed in most microfluidics can lead to the waste of unbound antibodies. Additionally, the antibodies present in the reaction solution usually have only one chance to interact with the antigens coated on the substrate. , While this approach reduces time consumption, it may potentially compromise the efficiency of antigen–antibody reactions.…”

High-speed fluidic processing circuits for dynamic control of haptic and robotic systems

“…Inclusion of a rigid SU-8 disk in the elastomer of the valve gate enabled pressure gain for cascadable logic ( 33 ), and fluidic oscillators provided the basis for clock timing on the chip ( 34 , 35 ), where the resistive-capacitive (RC) dynamics could be tuned by adding external capacitance to slow the oscillator ( 36 ) or adjusting the pull-down resistor to speed up the oscillator to a maximum of 50 Hz ( 37 ), albeit at the expense of reducing the output signal range. Recent work exploited the fluidic phenomenon of flow limitation to mimic a transistor’s saturation behavior, enabling a particle dispenser circuit without electronics ( 38 ). While these microfluidic logic circuits achieved notable success in academic labs, the peripheral electronics equipment required to drive them, from pressure regulators and sensors to solenoid valves and digital acquisition systems, has led to a relative lack of commercial success as some critics describe the resulting system as more of a “chip-in-a-lab” than a “lab-on-a-chip” ( 39 ).…”