Carlen, E. T., Weinberg, M. S., Zapata, A. M., & Borenstein, J. T. (2008). A micromachined surface stress sensor with electronic readout. Review of scientific instruments, 79(1), 015106.
A micromachined surface stress sensor has been fabricated and integrated off chip with a low-noise, differential capacitance, electronic readout circuit. The differential capacitance signal is modulated with a high frequency carrier signal, and the output signal is synchronously demodulated and filtered resulting in a dc output voltage proportional to the change in differential surface stress. The differential surface stress change of the Au(111) coated silicon sensors due to chemisorbed alkanethiols is 𝛥𝜎𝑠≈−0.42±0.0028Nm−1Δσs≈−0.42±0.0028Nm−1 for 1-dodecanethiol (DT) and 𝛥𝜎𝑠≈−0.14±0.0028Nm−1Δσs≈−0.14±0.0028Nm−1 for 1-butanethiol (BT). The estimated measurement resolution (1Hz1Hz bandwidth) is ≈0.12mNm−1≈0.12mNm−1 (DT: 0.2pgmm−20.2pgmm−2 and BT: 0.8pgmm−20.8pgmm−2) and as high as ≈3.82𝜇Nm−1≈3.82μNm−1 (DT: 8fgmm−28fgmm−2 and BT: 24fgmm−224fgmm−2) with system optimization.