A Sensitivity Enhancement Strategy for Capacitive Pressure Sensors Embedded in Microchannels via Reference Pressure Control

Pressure measurement in microchannels is crucial for understanding fluid flow behavior and advancing microfluidic device development. However, the micrometer-scale dimensions of microchannels impose significant constraints on the size and sensitivity of embedded pressure sensors, making insufficient sensitivity a primary challenge in pressure measurement. This study proposes a strategy to enhance the sensitivity of capacitive pressure sensors embedded in microchannels by controlling the reference pressure. First, by analyzing the nonlinear output of conventional circular capacitive pressure sensors operating in the normal mode, the sensitivity characteristics of the sensors are determined as the theoretical basis for the proposed strategy. Subsequently, based on this foundation, the core concept of the strategy is developed: adjusting the reference pressure to maintain the pressure difference across the pressure-sensing diaphragm within the range that ensures the required sensitivity for measurement. The unknown pressure to be measured is determined by subtracting the reference pressure from the measured pressure difference. Finally, a demonstration experiment is conducted to measure gas pressure fluctuations (0-0.10 kPa and 0-0.05 kPa, gauge pressure) and liquid sinusoidal pulsating flows with Reynolds numbers of 55-111, 111-166, and 166-222. The experimental results demonstrate that by controlling the reference pressure, the sensor sensitivity is 7.48-9.64 times that achieved under conventional atmospheric reference pressure conditions, effectively validating the feasibility and effectiveness of the proposed strategy.