This paper presents a catheter-based capacitive force sensor interface for cardiovascular diagnosis. The force sensor is implemented on a flexible printed circuit board (FPCB) substrate with a force-sensitive polydimethylsiloxane (PDMS), and a force-induced change in a capacitance of the sensor is measured by a precision capacitive sensor interface. To recover the performance degradation caused by the large parasitic capacitance C P of a long catheter, we present a parasitic insensitive analog front-end (AFE) with active C P cancellation, which employs a charge amplifier and a negative capacitor at the virtual ground of the charge amplifier. The prototype sensor was measured with a force loader in whole blood. The proposed AFE successfully cancels C P of 348 pF in a 0.9-m-long sensor and measurement results show the SNR of 53.8 dB and the capacitance resolution of 16 aF, a 19.6 dB improvement by canceling nonideal effect of C P. This corresponds to a force resolution of 2.22 gf, which is 9.29 × reduction compared to the work without the C Pcancellation. The proposed sensor interface is insensitive to C P from hundreds to 1-nF level, and the force-dependent stiffness of two different tissues has been successfully distinguished with an ex-vivo experiment. The proposed sensor interface enables the integration of capacitive force sensors in a smart catheter.
|Number of pages||12|
|Journal||IEEE Transactions on Biomedical Circuits and Systems|
|Publication status||Published - 2018 Aug|
Bibliographical noteFunding Information:
Manuscript received December 17, 2017; revised February 24, 2018 and April 10, 2018; accepted April 12, 2018. Date of publication June 15, 2018; date of current version August 15, 2018. This work was supported by the National Research Foundation of Korea (NRF) Grant funded by Mid-Career Researcher Program through NRF Grant funded by the MEST (2016R1A2B4010487). This paper was recommended by S.-Y. Lee. (Corresponding authors: WonHyoung Ryu and Youngcheol Chae.) S. Jeon is with the Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, South Korea, and also with LG Electronics, Seoul 07796, South Korea (e-mail:,email@example.com).
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All Science Journal Classification (ASJC) codes
- Biomedical Engineering
- Electrical and Electronic Engineering