Patent Publication Number: US-11029202-B2

Title: Radiation sensors

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 16/184,715 filed on Nov. 8, 2018, which is a divisional of U.S. patent application Ser. No. 15/217,955 filed on Jul. 22, 2016, which claims the benefit of priority to U.S. Provisional Application No. 62/198,039, filed Jul. 28, 2015, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to sensors, more specifically to ultraviolet sensors (e.g., for flame detection). 
     2. Description of Related Art 
     Traditional ultraviolet (UV) sensors can be used to detect flames, for example, for use with flame and smoke detectors. Flames emit UV radiation which can be detected by a suitable sensor. However, traditional flame sensors are fragile, complicated, and expensive to manufacture compared to traditional smoke detectors. Consequently, integration of smoke alarm and flame sensor in commercial and residential applications has had limited success to date. 
     Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved UV sensors. This can help to increase the adoption thereof in commercial and residential safety applications. The present disclosure provides a solution for this need. 
     SUMMARY 
     In accordance with at least one aspect of this disclosure, an ultraviolet radiation (UV) sensor includes a UV sensitive material and a first electrode and a second electrode connected in series through the UV sensitive material such that UV radiation can reach the UV sensitive material. 
     The UV sensitive material can include at least one of tin oxide, zinc tin oxide, magnesium oxide, magnesium zinc oxide, or zinc oxide. The electrodes can be interdigitated comb electrodes. 
     In certain embodiments, the UV sensitive material and the electrodes can be coplanar. For example, the UV sensitive material can be disposed in a space defined between the extensions of each comb electrode. 
     In certain embodiments, at least one of the electrodes and the UV sensitive material are at least partially transparent to UV radiation. For example, one or more of the electrodes can be UV-transparent electrodes. 
     The UV sensitive material can be a separate layer from the electrodes. In certain embodiments, each electrode can be separated by a layer of the UV sensitive material. In certain embodiments, the sensor can include a first layer of the UV sensitive material, a second layer having a second layer comb electrode with second layer comb electrode extensions, a third layer of UV sensitive material, and a fourth layer having a fourth layer comb electrode with fourth layer comb electrode extensions. Any suitable additional layers or reduction of layers are contemplated herein. For example, the sensor can further include a fifth layer of the UV sensitive material such that the fifth layer has a comb shape with fifth layer extensions that are less wide than the third layer. 
     The second layer comb electrode extensions can be narrower than the fourth layer comb electrode extensions or any other suitable width. In certain embodiments, the first layer can be a sheet and the third layer includes a comb shape with third layer extensions. 
     The sensor can have a planar shape, a curved shape such as cylindrical or elliptical, or any other suitable linear or nonlinear shape. For example, the sensor can have a curved shaped (e.g., cylindrical). In certain embodiments, the UV sensitive material can be disposed in a planar spiral relationship. Alternatively, sensor electrodes may have a spiral relationship on a cylindrical, hemi-spherical or otherwise non-planar concave or convex surface. 
     In certain embodiments, the sensor can include a conductive film separated from the electrodes by a dielectric for sensing capacitance between the conductive film and the electrodes. In certain embodiments, the dielectric can include the UV sensing material. 
     In accordance with at least one aspect of this disclosure, a method for manufacturing an ultraviolet (UV) sensor includes printing a UV sensitive material on or within a plurality of electrodes. In certain embodiments, the method can include printing the electrodes as described herein. 
     The sensitive material can be deposited or printed in a space between a plurality of electrode extensions. The method can further include forming the UV sensitive material to be coplanar with the electrodes to form a sensor layer. The method can include forming a plurality of the sensor layers one on top of another such that each sensor layer is electrically separated by the UV sensitive material but UV radiation is allowed to pass through each layer to reach the UV sensitive material in each sensor layer. 
     In accordance with at least one aspect of this disclosure, a radiation sensor includes a radiation sensitive material configured to be sensitive to one or more wavelengths of radiation and a first electrode and a second electrode connected in series through the radiation sensitive material such that radiation can reach the radiation sensitive material. 
     The radiation sensitive material can exhibit a greater absorbance of ultraviolet radiation than other adjacent radiation wavelength bands. A radiation sensitive material absorbance can decrease above wavelengths of about 200 nm. For example, the radiation sensitive material absorbance is at least about ten times higher at a portion of a band of wavelengths between about 100 nm and about 400 nm versus a band of wavelengths above 400 nm. In certain embodiments, the absorbance can drop about 80% at wavelengths higher than about 325 nm. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a plan view of an embodiment of a sensor in accordance with this disclosure, showing UV sensitive material disposed between first and second electrode extensions in a planar configuration; 
         FIG. 2A  is a partially exploded perspective view of another embodiment of a sensor with multiple sensing layers in accordance with this disclosure; 
         FIG. 2B  is an exploded plan view of each layer of the sensor of  FIG. 2A ; 
         FIG. 3  is an exploded plan view of each layer of another embodiment of a sensor in accordance with this disclosure, shown having air gaps increasing in size with each successive layer toward the outer surface; 
         FIG. 4  is a perspective view of another embodiment of a sensor in accordance with this disclosure, shown having a curved shape; 
         FIG. 5  is a plan view of another embodiment of a sensor in accordance with this disclosure, shown having a planar spiral shape; 
         FIG. 6  is partially exploded perspective view of another embodiment of a sensor in accordance with this disclosure, showing a conductive layer disposed in a capacitive relationship with the electrodes; and 
         FIG. 7  is a graph showing absorption of various embodiments of magnesium zinc oxide semiconductors. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a UV sensor in accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  100 . Other embodiments and/or aspects of this disclosure are shown in  FIGS. 2A-7  The systems and methods described herein can be used to reduce the cost and improve the performance of electromagnetic radiation sensors (e.g., UV sensors for flame detection). 
     In accordance with at least one aspect of this disclosure, an ultraviolet radiation (UV) sensor  100  includes a UV sensitive material  101 , a first electrode  103 , and a second electrode  105  connected in series through the UV sensitive material  101  such that UV radiation can reach the UV sensitive material  101 . As described herein, the UV sensitive material is configured to change a material property (e.g., conductivity) as a function of UV radiation exposure. 
     In certain embodiments, the UV sensitive material  101  can include at least one of tin oxide, zinc tin oxide, magnesium oxide, magnesium zinc oxide, or zinc oxide. Any other suitable material is contemplated herein for use in the sensitive material  101 , however, certain materials can be selected to minimize response to radiation other than UV (e.g., visible light, IR). 
     As shown, the electrodes  103 ,  105  can be interdigitated comb electrodes. This creates a space between each electrode extension  103   a ,  105   a  such that electrodes  103 ,  105  are not in direct electrical communication. The space between each electrode extension  103   a ,  105   a  can be selected to create a predetermined resistance (e.g., the smaller the spaces, the larger the current flow will be between electrodes  103   a ,  105   a ). Any other suitable shape of electrodes  103 ,  105  is contemplated herein. 
     In certain embodiments, as shown in  FIG. 1 , the UV sensitive material  101  and the electrodes  103 ,  105  can be coplanar. For example, the UV sensitive material  101  can be disposed in the space defined between the electrode extensions  103   a ,  105   a  of each electrode  103 ,  105 . Such a planar design can reduce the profile of the sensor and allow for wrapping, curving, and/or bending of the sensor  100  to any suitable shape. 
     The UV sensitive material  101  can be a separate layer from the electrodes  103 ,  105 . In certain embodiments, each electrode can be separated by a layer of the UV sensitive material  101 . For example, referring to  FIGS. 2A and 2B , a sensor  200  can include plurality of layers such that the sensor  200  has a stack or sandwich structure. For example, the sensor  200  includes a first layer  202  of the UV sensitive material  101 , a second layer  204  having a second layer comb electrode  203  with second layer comb electrode extensions  203   a , a third layer  206  of UV sensitive material  101 , and a fourth layer  208  having a fourth layer comb electrode  205   a  with fourth layer comb electrode extensions  205   a . As shown, the comb electrode extensions  203   a ,  205   a  can be interdigitated for each electrode, but any suitable electrode shape is contemplated herein (e.g., a perimeter shape defining and opening in the middle, a layer with a plurality of holes defined therethrough). The layers  202 ,  206  can have any suitable shape (e.g., interdigitated material extensions as shown). 
     In certain embodiments, as shown in  FIG. 2B , a dielectric layer  222  can be included at a bottom of the sensor  200 . This dielectric layer  222  may be reflective to enhance light collection by the sensor  200 . In certain embodiments, the dielectric layer  222  can be made from the UV sensitive material  101 , however, any other suitable dielectric material is contemplated herein. 
     Referring to  FIG. 3 , an embodiment of a sensor  300  can include a tapered construction such that layers toward the front of the device allow more UV radiation through to reach the back layers. For example, the fourth layer  308  can include a fourth layer comb electrode  305  with second layer comb electrode extensions  305   a  that are narrower than the second layer comb electrode extensions  303   a  of a second layer comb electrode  303  (e.g., to have larger spaces in the fourth layer  308  to allow more radiation to reach the first, second, and third layers  302 ,  304 ,  306 ). However, it is contemplated that each electrode extension  303   a ,  305   a  (or UV sensitive material extension) can have any suitable width, shape, and/or other dimensions relative to other extensions. 
     In certain embodiments, the first layer  302  can be a sheet of UV sensitive material  101  and the third layer  306  includes a comb shape with third layer extensions  307   a  of the UV sensitive material  101 . As shown, the sensor  300  can further include a fifth layer  310  of the UV sensitive material  101 . The fifth layer  310  can have a comb shape with fifth layer extensions  309   a  that are less wide than the third layer  306 . As described above, any other suitable shape for each layer of UV sensitive material is contemplated herein. 
     While the embodiments disclosed herein show a discrete number of layers (e.g., four, five), any suitable additional layers or reduction of layers is contemplated herein (e.g., two, three, ten). Further, certain stack or sandwich structures as shown in  FIGS. 2 and 3  can allow for sensitivity through a side of the stack as well as through the front and/or back. 
     In certain embodiments, at least one of the electrodes  103 ,  105 ,  303 ,  305  and the UV sensitive material  101  can be at least partially transparent to UV radiation (e.g., to enhance passage of UV radiation to layers in a stack). For example, one or more of the electrodes  103 ,  105 ,  303 ,  305  as described hereinabove can be made of any suitable transparent electrode material and/or in any suitable thickness to be partially transparent. For example, if the layers are made sufficiently thin (e.g., about less than 10 nm), certain transition metal oxides may be partially transparent. Any other suitable opacity is contemplated herein. 
     As described above, the sensor  100  can have any suitable shape. For example, referring to  FIG. 4 , sensor  400  can have a curved shaped (e.g., cylindrical, conical, tubular, non planar, hemispherical). For example, sensor layers may be directly deposited or printed onto a suitable non-planar shape. Alternatively, a planar sensor (e.g., sensor  100 ) can be deposited or printed on a flexible foil and can be wrapped to form curved sensor  400 . As shown, a solid piece of UV sensitive material  101  can be wrapped with comb electrodes  403 ,  405  (e.g., electrodes  403 ,  405  can be printed on to material  101 ). Any other suitable three-dimensional shape (e.g., rectilinear shapes, spherical) is contemplated herein. Such three-dimensional shapes can allow UV radiation to reach the UV sensitive material  101  from multiple angles and thereby increase the field of view without a focusing lens. 
     In another embodiment, referring to  FIG. 5 , the UV sensitive material  101  can be disposed in a planar spiral relationship with the electrodes  503 ,  505 . Any other suitable planar arrangement is contemplated herein. As described above, the spiral electrodes  503 ,  505  and UV sensitive material  101  may be deposited or printed onto any suitable non-planar shape (e.g., cylindrical, conical, hemispherical, rectilinear shapes, spherical). 
     Referring to  FIG. 6 , the sensors as described above (e.g., sensor  100  as shown) can include a conductive film  601  separated from the electrodes  103 ,  105  by a dielectric layer  622  for sensing capacitance between the conductive film  601  and the electrodes  103 ,  105 . In certain embodiments, the dielectric can be the UV sensing material  101 , but any other suitable dielectric (e.g., air, UV sensitive material  101 , or another insulator) is contemplated herein. The conductive film  601  may be the same material as the electrodes as described herein or any other suitable conductive material. 
     Sensors and/or components thereof as described above can be manufactured in any suitable manner. For example, sensors and/or components thereof as described above can be printed, sprayed, spin-coated, dipped, etched, or formed in any other suitable manner. 
     In accordance with at least one aspect of this disclosure, a method for manufacturing an ultraviolet (UV) sensor  100  includes deposition or printing a UV sensitive material  101  on or within a plurality of electrodes  103 ,  105 . In certain embodiments, the method can include deposition or printing the electrodes  103 ,  105  having any suitable construction as described above. 
     For example, the UV sensitive material  101  can be deposited or printed in a space between a plurality of electrode extensions  103   a ,  105   a . The method can further include forming the UV sensitive material  101  to be coplanar with the electrodes  103   a ,  105   a  to form a sensor layer. The method can include forming a plurality of the sensor layers one on top of another such that each sensor layer is electrically separated by the UV sensitive material  101  but UV radiation is allowed to pass through each layer to reach the UV sensitive material  101  in each sensor layer. 
     Referring to  FIG. 7 , the UV sensitive material can exhibit a greater absorbance of ultraviolet radiation than other adjacent radiation wavelength bands (e.g., visible wavelengths, x-ray wavelengths). As shown in  FIG. 7 , a UV sensitive material absorbance can decrease above wavelengths of about 200 nm for various magnesium zinc oxide compositions. For example, the UV sensitive material absorbance can be at least about ten times higher at a portion of a band of wavelengths between about 100 nm and about 400 nm versus a band of wavelengths above 400 nm. In certain embodiments, the absorbance can drop about 80% at wavelengths higher than about 325 nm for certain zinc tin oxide compounds. (See “Caihong Liu, Haiyan Chen, Zheng Ren, Sameh Dardona, Martin Piech, Haiyong Gao and Pu-Xian Gao, Controlled Synthesis and Structure Tunability of Photocatalytically Active Mesoporous Metal-based Stannate Nanostructures, Appl. Surf. Sci., 2014, 296, 53-60.”). 
     While the embodiments hereinabove are described as being configured for UV radiation sensing, it is contemplated that certain embodiments of sensors can be configured (e.g., via suitable material selection of the sensitive material) to be sensitive to any other wavelength of radiation (e.g., visible, infrared). 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for radiation sensors with superior properties including improved performance and reduced cost. While the apparatus and methods of the subject disclosure have been shown and described with reference to embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.