Photoacoustic sensor using micromachined ultrasonic transducers

An apparatus for estimating one or more cardiac features, the apparatus comprising:

• a substrate comprising a printed circuit board, a flexible circuit board, or a combination thereof;
• a light source system comprising a plurality of light-emitting elements mounted on a major surface of the substrate;
• an ultrasonic receiver system comprising an array of piezoelectric micromachined ultrasonic transducers (PMUTs) formed on the major surface of the substrate, wherein the array of PMUTs is configured to operate at different resonant frequencies;
• a control system formed on the major surface of the substrate;
• and
• an encapsulation layer disposed over the plurality of light-emitting elements, the array of PMUTs, and the control system so that the plurality of light-emitting elements, the array of PMUTs, and the control system are enclosed within a material of the encapsulation layer, wherein a thickness of the apparatus is equal to or less than 4 mm;
• wherein the control system is configured with instructions to perform the following operations:
• cause the light source system to emit light towards human tissue in contact with an outer surface of the encapsulation layer;
• receive ultrasonic signals from each of the PMUTs in the ultrasonic receiver system corresponding to ultrasonic waves generated by the human tissue;
• identify one or more blood vessels;
• and
• estimate one or more cardiac features based, at least in part, on the one or more blood vessels.

A method of detecting a blood vessel, the method comprising:

• causing a light source system comprising one or more light-emitting chips mounted on a major surface of a substrate to emit light towards a target object, wherein the substrate comprises a printed circuit board, a flexible circuit board, or a combination thereof;
• receiving, from an ultrasonic receiver system formed on the major surface of the substrate, signals corresponding to ultrasonic waves caused by a photoacoustic response of the target object to light emitted by the light source system, wherein the ultrasonic receiver system comprises an array of piezoelectric micromachined ultrasonic transducers (PMUTs), wherein the array of PMUTs is configured to operate at different resonant frequencies, wherein the ultrasonic receiver system and the light source system are enclosed within a material of an encapsulation layer;
• amplifying the signals corresponding to the ultrasonic waves;
• producing a beamformed ultrasonic receiver image;
• and
• detecting a blood vessel within the target object based, at least in part on the beamformed ultrasonic receiver image, wherein a thickness of an apparatus performing the method comprising the encapsulation layer, the substrate, the ultrasonic receiver system, and the light source system is equal to or less than 4 mm.