Exploiting broader dynamic range in Si-bridge modified QTF's for sensitive thermometric applications

The response of modified Quartz Tuning Forks (QTFs) on affixing an opto- or chemo-responsive bridging element between the terminal ends of the fork have been demonstrated to be both selective and highly sensitive. However, the Hookean model, widely employed in analysis currently, substantiates numerical accuracy when the stiffness of the bridging element is much smaller than that of the QTF motional arm. This paper presents a distributed beam model applicable for a broader range of stiffness ratios of the respective parts and is tested using a silicon bridging element to detect optically mediated thermal responses. Using this approach we demonstrate a sensor responsivity (ℜ) of 23 kN/m W, and a Noise Equivalent Power (NEP) of 8.5×10⁻⁷ W. The minimum detectable change in temperature of the bridge sensing element is calculated to be 2 mK. Thus, employing silicon bridging elements as demonstrated here, offers greater control over the reproducibility of the modified QTF over that of individually affixed polymer strands, as well as affords the opportunity to expand device reproducibility for larger scale implementation.