Integration of a capacitive pressure sensing system into the outer catheter wall for coronary artery FFR measurements

Frank Stam, Heikki Kuisma, Feng Gao, Jaakko Saarilahti, David Gomes Martins, Anu Kärkkäinen, Brendan Marrinan, Sebastian Pintal

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review


The deadliest disease in the world is coronary artery disease (CAD), which is related to a narrowing (stenosis) of blood vessels due to fatty deposits, plaque, on the arterial walls. The level of stenosis in the coronary arteries can be assessed by Fractional Flow Reserve (FFR) measurements. This involves determining the ratio between the maximum achievable blood flow in a diseased coronary artery and the theoretical maximum flow in a normal coronary artery. The blood flow is represented by a pressure drop, thus a pressure wire or pressure sensor integrated in a catheter can be used to calculate the ratio between the coronary pressure distal to the stenosis and the normal coronary pressure. A 2 Fr (0.67mm) outer diameter catheter was used, which required a high level of microelectronics miniaturisation to fit a pressure sensing system into the outer wall. The catheter has an eccentric guidewire lumen with a diameter of 0.43mm, which implies that the thickest catheter wall section provides less than 210 microns height for flex assembly integration consisting of two dies, a capacitive MEMS pressure sensor and an ASIC. In order to achieve this a very thin circuit flex was used, and the two chips were thinned down to 75 microns and flip chip mounted face down on the flex. Many challenges were involved in obtaining a flex layout that could wrap into a small tube without getting the dies damaged, while still maintaining enough flexibility for the catheter to navigate the arterial system.
Original languageEnglish
Title of host publicationBio-MEMS and Medical Microdevices III
EditorsIoanna Giouroudi, Ioanna Giouroudi, Manuel Delgado-Restituto, Sander van den Driesche
ISBN (Electronic)9781510609952
Publication statusPublished - 1 Jan 2017
MoE publication typeA4 Article in a conference publication
EventBio-MEMS and Medical Microdevices III Conference 2017 - Barcelona, Spain
Duration: 9 May 201710 May 2017

Publication series

SeriesProceedings of SPIE


ConferenceBio-MEMS and Medical Microdevices III Conference 2017


  • capacitive pressure sensor
  • catheter integration
  • chip bumping & coining
  • die thinning
  • flexible circuit
  • flip chip interconnect
  • fractional Flow Reserve (FFR)
  • solder laser jetting
  • Fractional Flow Reserve (FFR)
  • OtaNano

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