A chemofluidic oscillator circuit that employs a hydrogel‐based chemofluidic transistor for chemical‐fluidic coupling is presented. It shows a period between 200 and 1000 s and alcohol concentrations oscillating between 2 wt% and 10 wt%. Because of the direct interaction with chemistry, chemofluidic transistors have the potential to facilitate labs‐on‐chips with enhanced functionality and scalability.

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Despite great progress of lab‐on‐a‐chip (LoC) technology platforms in the last 30 years, there is a lack of standardized microfluidic components, real on‐chip automation and progressive functional scalability of the fluidic circuits. Hydrogel‐based microfluidic circuits have a high scaling potential and provide on‐chip automation, but are complex in system design. An advanced circuit concept for planar microfluidic chip architectures, originating from the early era of the semiconductor‐based resistor‐transistor‐logic (RTL) is presented and the hydrogel‐based chemical volume phase transition transistor (CVPT) for logic gate operations is implemented. The circuit concept (CVPT‐RTL) is robust and simple in design, feasible with common materials and manufacturing techniques of the LoC technology. Thereby, three major challenges are solved: contamination issues, maintaining the signal compliance for cascadability, and chemical signal inversion. As a central element, a CVPT cascode is introduced. The functionality of the concept is verified by a 24 h test of the NAND gate operation and a self‐automated chemofluidic analog‐to‐digital converter, utilized as interface between bioreactors and extended microfluidic logic circuits. Moreover, the CVPT‐RTL cascode demonstrates the expected self‐stabilizing performance of the NAND gate. Accompanying simulations of the component behavior based on a network description implemented in Matlab Simscape match with the experimental results.

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