1. Development of a Smart Stent Graft SenseCardioHealth Luis A. Rocha

2. Aneurysm An aneurysm is a permanent and irreversible localized dilatation of an artery, having at least a 50% increase in diameter compared with the common one.

3. Treatment options  Endovascular aneurysm repair - EVAR  Open surgery

4. EVAR - Surveillance protocol required ENDOLEAKs - defined by the persistence of blood flow outside the lumen f the endoluminal graft but within an aneurysm sac or adjacent vascular segment being treated by the graft. Various types of endoleak: type I: leak at the attachment site type II: leak from a branch artery type III: graft defect type IV: graft porosity. Objective – Next generation of stent-grafts with built-in diagnostic capabilities (smart stent-graft)

5. How to detect endoleaks?  EVAR Procedure After EVAR aneurysm sac is depressurized If endoleaks, or stent-graft migration occur, pressure in the aneurysm sac will increase The pressure inside the aneurysm sac is a good indicator for post- EVAR surveillance

6. How to detect endoleaks?  Abdominal Aortic Aneurysm (AAA) Model

7. AAA Model  Without stent-graft

8. AAA Model  With stent-graft Pressure ranges between 14-22 mmHg in the aneurysm sac

9. Smart Stent-Graft  Challenges Thin Fit inside the catheter without increasing catheter size Flexible Must cross a tortuous path till the deployment site No internal power supply Multiple sensors Improve knowledge of aneurysm behavior after EVAR procedure Smart stent- graft stent graft sensor telemetric system

10. Sensor - communication  System level definition Frequency band – 12.5 MHz to 20.0 MHz (allocated for medical applications) Block diagram Model

11. Sensor - communication  1 st prototype (PCB using COTS) Multiple sensors

12. Pressure sensor  Working principle

13. Pressure sensor – main specifications ACCURACYRANGE +/- 3 mm Hg or +/- 2% of reading (whichever is greater) 20 to 250 mm Hg Indicated pressure should be less than 23 mmHg input pressure greater than 0 but less than 20 mm Hg Indicated pressure should be 0 +/- 3 mmHg input pressure less than or equal to 0 mmHg Indicated pressure should be greater than 245 mmHg or an over range as indicated input pressure greater than 250 mmHg ProblemMeasurement location Typical values (mmHg) Measurement range (mmHg) Measurement resolution (mmHg) Measurement absolute accuracy (mmHg) Signal bandwidth (Hz) Arterial diameter (mm) Heart failurePulmonary artery8 to 300 to 1000.320 to 20025 to 35 Coronary artery disease Downstream of stent or blockage 60 to 15020 to 250150 to 803 to 5 Aortic aneurysm Between graft and aneurysm wall 20 to 9020 to 250150 to 8015 to 40 Hypertension and autonomic dysreflexia Artery60 to 15020 to 250250 to 202 to 20 ANSI/AAMI SP-10-1992 national standard for electronic or automated sphygmomanometers

14. Sensor fabrication process - moulds Negative MasksSU-8 Structures SU-8 Glass plate  SU-8 Characteristics Multifunctional photoresist resin Excellent lithography properties Ultra thick structure, good sidewall quality and fine optical characteristics Good for X-ray and UV lithography applications High structural ratio  CNC - Drilling Acrylic Lower costs Faster production time Lower dimensional control SU-8 Acrylic

15.  Aligned carbon-nanotube growth Deposition of Fe/Al 2 O 3 on a silicon substrate Patterning of catalyst Chemical vapor deposition of CNT Quartz tube furnace Ethylene as precursor gas 750º  Advantages High purity High yield Vertical alignment Sensor fabrication process – CNT growth

16. Sensor fabrication process – PDMS  Polydimethylsiloxane (PDMS) SYLGARD®184 Silicone Elastomer (Dow Corning) Biocompatible Chemically inert, thermally stable, permeable to gases, simple to handle, exhibits isotropic and homogeneous properties Exhibit higher sensitivity (Young’s modulus less than100 MPa) and very high permeability to oxygen PDMS S=11.43 Sm -1 Conductivity

17. Sensor fabrication process – PDMS  Mechanical Tests rectangular membranes: 32 x 14 x 0.4 mm 3 Elastic Modulus – 2.4MPa Tensile Strength – 0.87MPa

18. Sensor fabrication process

19. Sensor - simulations

20. SenseCardioHealth Research Team Luis A. Rocha (UMinho/IPC) – Principal Investigator University of Minho Julio Viana (IPC) António Pontes (IPC) Alexandra Sepulveda (LTI) FEUP José Machado da Silva (INESC Porto) Joaquim Gabriel Mendes (IDMEC) João Tavares (INEGI) Isa Santos (LTI) Alfredo Moreira (Scholarship) Instituto Superior Técnico Alexandra Rodrigues (ICEMS) Bin Li (ICEMS) Lígia Figueiredo (Scholarship) Massachusetts Institute of Technology Brian Wardle (MPC and MEMS@MIT) Fabio Fachin Collaborators Roncon de Albuquerque (HSJ) Sergio Sampaio (HSJ) Anabela Carvalho (ICS/UMinho)