ULTRASONIC PLATFORM BASED ON HIGH FREQUENCY PMUTS-ON-CMOS ARRAYS

THE GENERAL GOAL OF THIS RESEARCH PROPOSAL IS TO DEMONSTRATE THE CAPABILITIES AND PERFORMANCE OF A MEMS-BASED TECHNOLOGICAL PLATFORM TO PROVIDE ENHANCED PERFORMANCE ULTRASOUND IMAGING/TREATMENT IN MEDICAL APPLICATIONS TO BE USED IN HIGH-DEMANDING IMAGING APPLICATIONS (AS IN-BODY INSPECTION THROUGH INTRAVASCULAR ULTRASOUND MEDICAL DIAGNOSIS, IVUS, OR IN WEARABLES DEVICES, IN WHICH NON-INTRUSIVE/INVASIVE SYSTEMS FOR RAPID LIFE VITAL SIGNS EVALUATION ARE DESIRED AND DEMAND A VERY LOW SIZED SYSTEM) AS WELL AS TO ASSESS POSSIBILITIES FOR MEDICAL TREATMENT THROUGH ULTRASONIC NEUROMODULATION. THIS ULTRASONIC PLATFORM WILL BE BASED ON PIEZOELECTRICAL MICROMACHINED ULTRASOUND TRANSDUCERS (PMUTS) WHICH ARE MONOLITHICALLY INTEGRATED OVER THE ANALOG FRONT-END (AFE) CMOS PROCESSING CIRCUITRY, PMUT-ON-CMOS, IN WHICH WE HAVE BEEN WORKING AND DEVELOPING DURING OUR LAST PROJECT (PID2019-108270RB-I00). BASED ON THE RESULTS ACHIEVED, WE WILL CONSTRUCT NEW SYSTEMS CAPABLE OF ACCOMPLISHING SPECIFICATIONS FOR REAL ULTRASONIC MEDICAL APPLICATIONS. IN ADDITION TO THIS TECHNOLOGICAL APPROACH, WE WILL CONTRIBUTE TO THE KNOWLEDGE GENERATION, DEVELOPING NEW PARADIGMS WITH THE EXPLORATION OF NEUROMODULATION TECHNIQUES USING THE ULTRASONIC DEVELOPMENT PLATFORM, DEMONSTRATING THE CAPABILITIES OF THE PLATFORM FOR OBTAINING ARBITRARY ACOUSTIC FIELDS (IN 2D AND 3D) WHICH COULD EVENTUALLY SERVE FOR THESE PURPOSES (I.E., ACTUATION OF THE RETINA). AS SECOND CONTRIBUTION TO KNOWLEDGE GENERATION, WE ALSO AIM TO DEMONSTRATE NEW PARADIGMS WITH THE EXPLORATION OF NON-LINEAR BEHAVIOR OF THE PMUTS AND POSSIBILITIES TO USE HIGHER FREQUENCY HARMONICS (ALREADY OBTAINED IN AIR-PMUT ACTUATED DEVICES), TO ENHANCE ULTRASONIC IMAGING PERFORMANCE (RESOLUTION AND FIELD-OF-VIEW). THE SPECIFIC OBJECTIVES ARE: -DEVELOPMENT OF PMUTS ARRAYS PROVIDING ACOUSTIC IMAGING IN A PULSE-ECHO SCHEME WITH 10 UM RESOLUTION AT AXIAL DISTANCES IN THE CM RANGE WITH OPERATIONAL FREQUENCIES HIGHER THAN 20 MHZ. POSSIBILITY OF DUAL FREQUENCY OPERATION IS ALSO ENVISIONED. -INCREASE THE OPERATIVE FREQUENCY BANDWIDTH TOWARDS A 100% FRACTIONAL BAND ALLOWING FASTER IMAGING CAPABILITIES IN PULSE-ECHO SCHEMES, WITH TWO APPROACHES: MERGING OF DIFFERENT SIZED PMUTS IN A COUPLED ARRAY ARRANGEMENT FOLLOWING A FILTER DESIGN APPROACH; OR MODIFYING THE PMUT LAYOUT. -DESIGN OF CMOS READ-OUT OF THE ARRAYS FOR HIGH SNR. TRADE-OFFS BETWEEN NUMBER OF READINGS PMUTS IN THE ARRAY, TO ENHANCE SIGNAL AND INCREASE OF ASSOCIATED PARASITIC CAPACITANCE WILL BE ANALYZED AND SPECIFIC READ-OUT CMOS CIRCUIT WILL BE DESIGNED FOR THIS OPTIMIZATION. -STUDY THE VIABILITY OF ARBITRARY-SHAPE ULTRASONIC FIELD FOR NEUROMODULATION. -ESTABLISHMENT OF THE INDIVIDUAL PROCESSES FOR THE MICROFABRICATION OF THE PROTECTIVE LAYER NEEDED OVER THE ULTRASOUND SOURCES COMBINING FRESNEL LENS AND HOLEY-STRUCTURED METAMATERIAL FOR FOCUSING AND ENHANCE RESOLUTION WHILE PROVIDING PROTECTION TO THE ULTRASOUND SYSTEM. -EXPLORE THE USE OF PMUTS IN A NONLINEAR REGIME TO GENERATE MULTIPLE HARMONICS (SUPERHARMONICS) AND THEIR USE FOR ACOUSTIC PRESSURE PULSE-ECHO IMAGING SYSTEMS. THE ACHIEVEMENT OF THESE GOALS WILL NEED DEVELOPMENT OF NEW PMUT LAYOUT/DEVICES, DEVELOPMENT OF NEW CMOS CIRCUITRY INCLUDING TIME-GAIN VARIABLE AMPLIFICATION AND DESIGN OF HIGHER DIMENSION ARRAYS FOR AN EFFICIENT ACOUSTIC IMAGING SYSTEM, AS IS DETAILED IN THE WORKING PLAN.