Patent Publication Number: US-2017367680-A1

Title: Ultrasonic sensor for health monitoring

Description:
FIELD 
     The subject matter herein generally relates to an ultrasonic sensor, particularly to an ultrasonic sensor for health monitoring. 
     BACKGROUND 
     Ultrasonic sensors have many advantages such as small size, cheap price, safety, and widespread use in medical devices. The ultrasonic sensor for medical diagnosis is attached to a user&#39;s skin to emit ultrasonic waves. However, results obtained from the ultrasonic sensor may not be accurate when air is positioned between the ultrasonic sensor and the user&#39;s skin. Therefore, there is room for improvement in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is cross-sectional view of a first exemplary embodiment of an ultrasonic sensor. 
         FIG. 2  is cross-sectional view of a signal transmitting layer of the ultrasonic sensor of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “comprising” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like. 
       FIG. 1  illustrates an ultrasonic sensor  20  according to an exemplary embodiment. The ultrasonic sensor  20  can be used in an electronic device configured for placement on a user&#39;s skin and to assist in medical monitoring. A user&#39;s health characteristics such as blood flow, blood pressure, and heart rate can thus be constantly monitored. 
     The ultrasonic sensor  20  includes a substrate  21 , a signal receiving layer  22 , a signal transmitting layer  23 , a flexible layer  24 , and a protecting layer  154 . In this exemplary embodiment, the ultrasonic sensor  20  has a curved shape (e.g. arc shape) to fit a user&#39;s body or a part of the body. The signal receiving layer  22  is coupled to a surface of the substrate  21  by a first adhesive layer  27 . The signal transmitting layer  23  is coupled by a second adhesive layer  26  to a surface of the substrate  21  facing away from the signal receiving layer  22 . In this exemplary embodiment, the first adhesive layer  27  and the second adhesive layer  26  are flexible. 
     The flexible layer  24  is formed on a surface of the signal receiving layer  22  facing away from the signal transmitting layer  23 . The flexible layer  22  includes a contact surface  241  which faces away from the signal receiving layer  22 . The contact surface  241  directly contacts the user&#39;s skin when using the ultrasonic sensor  20 . The flexible layer  24  is configured to protect the signal receiving layer  22 . The flexible layer  22  can be made of a common flexible material (e.g. latex or rubber). The flexible layer  22  can thus fit any part of the user&#39;s body and be close-fitting on the user&#39;s skin. In this exemplary embodiment, the flexible layer  22  has a curved shape (e.g. arc shape). In addition, the flexible layer  22  is soft to the touch, and comfortable to wear on the user&#39;s skin. 
     The protecting layer  25  is formed on a surface of the signal transmitting layer  23  facing away from the signal receiving layer  22 . The protecting layer  25  is configured to protect the signal transmitting layer  23 . 
     A plurality of thin film transistors  210  are formed on the substrate  150 . The plurality of thin film transistors  210  are arranged in an array and are electrically coupled to the signal receiving layer  22 . The thin film transistors  210  are configured to receive electrical signals from the signal receiving layer  22 , convert the electrical signals to data signals for images or information in other form. 
     In this exemplary embodiment, the substrate  21  can be made of a flexible material, such as polyimide or polyethylene terephthalate. The substrate  21  has a curved shape (e.g. arc shape) to make the ultrasonic sensor  20  fit the user&#39;s body (e.g. arm or wrist). In some embodiments, the substrate  21  is made of a rigid material, such as glass, and has a curved shape (e.g. arc shape) to fit the user&#39;s body (e.g. arm or wrist). 
     The signal transmitting layer  23  is configured to emit ultrasonic waves continuously. The signal receiving layer  22  is configured to receive ultrasonic waves reflected by a human body or part to which the ultrasonic sensor  20  is attached. The signal receiving layer  22  includes a first piezoelectric material layer  221  and a first electrode layer  222  positioned on the first piezoelectric material layer  221 . The first piezoelectric material layer  221  is coupled to the substrate  21  by the first adhesive layer  27 . That is, the first adhesive layer  27  is positioned between the substrate  21  and the first piezoelectric material layer  221 . 
     The signal transmitting layer  23  includes a second electrode layer  233  and a plurality of piezoelectric units  230  formed on the second electrode layer  233 , wherein the piezoelectric units  230  are closer to the substrate  21  than the second electrode layer  233  to the substrate  21 . The piezoelectric units  230  are separated from each other. Each piezoelectric unit  230  includes a second piezoelectric material layer  232  formed on the second electrode layer  233  and a conductive layer  231  formed on the second piezoelectric material layer  232  facing away from the second electrode layer  233 . A method for making the piezoelectric units  230  may include the following steps: forming a continuous piezoelectric material layer (not shown) on the second electrode layer  233 , forming a continuous conductive material layer (not shown) on the continuous piezoelectric material layer, and etching and patterning the continuous piezoelectric material layer and the continuous conductive material layer. 
     Referring now to  FIG. 1  and  FIG. 2 , each second piezoelectric material layer  230  is able to vibrate and emit ultrasonic waves when a voltage is applied between the second electrode layer  233  and the corresponding conductive layer  231 . Each piezoelectric unit  230  can emit ultrasonic waves independently, which is called “beam forming mode”. In the beam forming mode, ultrasonic waves emitted from one piezoelectric unit  230  overlap with ultrasonic waves emitted from other piezoelectric units  230 , which effectively improve the intensity of the ultrasonic waves from the signal transmitting layer  23 . In this embodiment, the piezoelectric units  230  can emit ultrasonic waves at a same time. In other embodiments, the piezoelectric units  230  can emit ultrasonic waves in a certain order, for example, the piezoelectric units  230  can emit ultrasonic waves in order from leftmost to rightmost. The piezoelectric units  230  can emit ultrasonic waves having a same intensity or different intensities. 
     The first piezoelectric material layer  221  and the second piezoelectric material layer  232  can be made of polyvinylidene fluoride (PVDF). The first electrode layer  222 , the second electrode layer  233 , and the conductive layer  231  can be made of a same electrically conductive material or different electrically conductive materials. 
     As an example of when in use, the ultrasonic sensor  20  is attached to a user&#39;s skin by attaching the flexible layer  24  on the user&#39;s skin (e.g. wrist). A voltage is applied between the second electrode layer  233  and the conductive layer  231 , and the second piezoelectric material layer  232  vibrates and emits ultrasonic waves. The ultrasonic waves pass through the substrate  21 , the signal receiving layer  22 , the flexible layer  24 , and the user&#39;s skin to reach internal organs or elements of the body, and a portion of the ultrasonic waves is reflected to the signal receiving layer  22 . The reflected ultrasonic waves would be changed according to the status of the internal organs or elements of the body they encounter, thus vibration of the first electrode layer  222  would be changed. The signal receiving layer  152  converts the received ultrasonic wave signals to electrical signals and transmits the electrical signals to the thin film transistors  210 . The thin film transistors  210  convert the electrical signals to data signals. 
     In other embodiments, the ultrasonic sensor  20  may further include a storage device (not shown). The results of monitoring (e.g. data signals) can be stored in the storage device. In some embodiments, the ultrasonic sensor  20  may be coupled to an outside readout device (not shown) by wires, WIFI, or BLUETOOTH, and the outside readout device may display the results as images or as information in other form. The outside readout device can be a mobile phone or a computer. 
     In some embodiments, the ultrasonic sensor  20  may be integrated with a display panel (not shown) and configured to display the data signals from the ultrasonic sensor  20 . The user can observe the images or other information on the display panel. The display panel may be a known organic light emitting diode (OLED) display panel or a known liquid crystal display (LCD) panel. For example, the display panel may be a flexible OLED display panel, so the ultrasonic sensor  20  integrated with the display panel can be attached to the body or part of the user. The display panel may be an LCD panel having a curved shape to fit the body of the user. 
     When the ultrasonic sensor  20  is integrated with a display panel (not shown), a shielding layer (not shown) may be positioned between the ultrasonic sensor  20  and the display panel. The shielding layer may cover at least one surface of the ultrasonic sensor. The shielding layer may be made of an electrically conductive material and configured to shield the ultrasonic sensor  20  from electrical activity and radiation in the display panel. In addition, the shielding layer may be flexible. In some embodiments, the shielding layer  13  may cover at least two surfaces of the ultrasonic sensor  20 , substantially enclosing the ultrasonic sensor  20  with a shield. 
     It is to be understood, even though information and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the present embodiments, the disclosure is illustrative only; changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present embodiments to the full extent indicated by the plain meaning of the terms in which the appended claims are expressed.