{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T17:09:04Z","timestamp":1785863344972,"version":"3.56.0"},"reference-count":42,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2022,10,20]],"date-time":"2022-10-20T00:00:00Z","timestamp":1666224000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"the National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["11974093"],"award-info":[{"award-number":["11974093"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"the National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["XNAUEA5640201720-09"],"award-info":[{"award-number":["XNAUEA5640201720-09"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"the National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["IR2021238"],"award-info":[{"award-number":["IR2021238"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Heilongjiang Touyan Innovation Team Program","award":["11974093"],"award-info":[{"award-number":["11974093"]}]},{"name":"Heilongjiang Touyan Innovation Team Program","award":["XNAUEA5640201720-09"],"award-info":[{"award-number":["XNAUEA5640201720-09"]}]},{"name":"Heilongjiang Touyan Innovation Team Program","award":["IR2021238"],"award-info":[{"award-number":["IR2021238"]}]},{"name":"Medical Engineering (Science) cross research fund of Harbin Institute of Technology","award":["11974093"],"award-info":[{"award-number":["11974093"]}]},{"name":"Medical Engineering (Science) cross research fund of Harbin Institute of Technology","award":["XNAUEA5640201720-09"],"award-info":[{"award-number":["XNAUEA5640201720-09"]}]},{"name":"Medical Engineering (Science) cross research fund of Harbin Institute of Technology","award":["IR2021238"],"award-info":[{"award-number":["IR2021238"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>High-performance broadband ultrasound transducers provide superior imaging quality in biomedical ultrasound imaging. However, a matching design that perfectly transmits the acoustic energy between the active piezoelectric element and the target medium over the operating spectrum is still lacking. In this work, an anisotropic gradient acoustic impedance composite material as the matching layer of an ultrasonic transducer was designed and fabricated; it is a non-uniform material with the continuous decline of acoustic impedance along the direction of ultrasonic propagation in a sub-wavelength range. This material provides a broadband window for ultrasonic propagation in a wide frequency range and achieves almost perfect sound energy transfer efficiency from the piezoelectric material to the target medium. Nano tungsten particles and epoxy resin were selected as filling and basic materials, respectively. Along the direction of ultrasonic propagation, the proportion of tungsten powder was carefully controlled to decrease gradually, following the natural exponential form in a very narrow thickness range. Using this new material as a matching layer with high-performance single crystals, the \u22126 dB bandwidth of the PMN-PT ultrasonic transducer could reach over 170%, and the insertion loss was only \u221220.3 dB. The transducer achieved a temporal signal close to a single wavelength, thus there is the potential to dramatically improve the resolution and imaging quality of the biomedical ultrasound imaging system.<\/jats:p>","DOI":"10.3390\/s22208025","type":"journal-article","created":{"date-parts":[[2022,10,21]],"date-time":"2022-10-21T00:34:30Z","timestamp":1666312470000},"page":"8025","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":41,"title":["Enhancement of Ultrasonic Transducer Bandwidth by Acoustic Impedance Gradient Matching Layer"],"prefix":"10.3390","volume":"22","author":[{"given":"Ke","family":"Zhu","sequence":"first","affiliation":[{"name":"Functional Materials and Acousto-Optic Instruments Institute, School of Physics, Harbin Institute of Technology, Harbin 150080, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jinpeng","family":"Ma","sequence":"additional","affiliation":[{"name":"Functional Materials and Acousto-Optic Instruments Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, Harbin 150080, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xudong","family":"Qi","sequence":"additional","affiliation":[{"name":"Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bingzhong","family":"Shen","sequence":"additional","affiliation":[{"name":"Functional Materials and Acousto-Optic Instruments Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, Harbin 150080, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yang","family":"Liu","sequence":"additional","affiliation":[{"name":"Functional Materials and Acousto-Optic Instruments Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, Harbin 150080, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Enwei","family":"Sun","sequence":"additional","affiliation":[{"name":"Functional Materials and Acousto-Optic Instruments Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, Harbin 150080, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rui","family":"Zhang","sequence":"additional","affiliation":[{"name":"Functional Materials and Acousto-Optic Instruments Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology, Harbin 150080, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"499","DOI":"10.1038\/nature16066","article-title":"Ultrafast ultrasound localization microscopy for deep super-resolution vascular imaging","volume":"527","author":"Errico","year":"2015","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1685","DOI":"10.1016\/j.ejrad.2015.03.016","article-title":"Ultrasound molecular imaging: Moving toward clinical translation","volume":"84","author":"Bachawal","year":"2015","journal-title":"Eur. J. Radiol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"487","DOI":"10.3949\/ccjm.72.6.487","article-title":"Intravascular ultrasonography: Using imaging end points in coronary atherosclerosis trials","volume":"72","author":"Schoenhagen","year":"2005","journal-title":"Clevel. Clin. J. Med."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"662","DOI":"10.1038\/nmeth.1641","article-title":"Functional ultrasound imaging of the brain","volume":"8","author":"Montaldo","year":"2011","journal-title":"Nat. Methods"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"6447","DOI":"10.1088\/0031-9155\/58\/18\/6447","article-title":"Acoustic super-resolution with ultrasound and microbubbles","volume":"58","author":"Viessmann","year":"2013","journal-title":"Phys. Med. Biol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"5023","DOI":"10.1038\/ncomms6023","article-title":"Functional ultrasound imaging of intrinsic connectivity in the living rat brain with high spatiotemporal resolution","volume":"5","author":"Osmanski","year":"2014","journal-title":"Nat. Commun."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1109\/51.544509","article-title":"Ultrasonic transducers and arrays","volume":"15","author":"Shung","year":"1996","journal-title":"IEEE Eng. Med. Biol. Mag."},{"key":"ref_8","unstructured":"Hoskins, P.R., Thrush, A., and Martin, K. (2003). Diagnostic Ultrasound, Greenwich Medical Media Limited."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"298","DOI":"10.1007\/PL00014060","article-title":"Boardband transducers","volume":"9","author":"Whittingham","year":"1999","journal-title":"Eur. Radiol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"223","DOI":"10.1016\/j.sna.2011.04.004","article-title":"Fabrication of angle beam two-element ultrasonic transducers with PMN\u2013PT single crystal and PMN\u2013PT\/epoxy 1\u20133 composite for NDE applications","volume":"168","author":"Zhang","year":"2011","journal-title":"Sensors Actuators A Phys."},{"key":"ref_11","first-page":"623","article-title":"Matching layer optimization between ultrasound transducer and human tissues","volume":"1","author":"Xiang","year":"1995","journal-title":"Proc. IEEE Ultrason. Symp. Eng. Med. Biol. Soc."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1109\/T-SU.1966.29370","article-title":"The Effects of Backing and Matching on the Performance of Piezoelectric Ceramic Transducers","volume":"13","author":"Kossoff","year":"1966","journal-title":"IEEE Trans. Sonics Ultrason."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1109\/T-SU.1975.30776","article-title":"Multilayer Impedance Matching Schemes for Broadbanding of Water Loaded Piezoelectric Transducers and High Q Electric Resonators","volume":"22","author":"Goll","year":"1975","journal-title":"IEEE Trans. Sonics Ultrason."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"614","DOI":"10.1016\/j.ultras.2013.08.015","article-title":"Microfabrication of stacks of acoustic matching layers for 15MHz ultrasonic transducers","volume":"54","author":"Manh","year":"2014","journal-title":"Ultrasonics"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"094908","DOI":"10.1063\/1.3065476","article-title":"Multiple matching scheme for broadband 0.72Pb(Mg1\/3Nb2\/3)O3-0.28PbTiO3 single crystal phased-array transducer","volume":"105","author":"Lau","year":"2009","journal-title":"J. Appl. Phys."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"624","DOI":"10.1109\/TUFFC.2004.1320834","article-title":"Acoustic Impedance Matching of Piezoelectric Transducers to the Air","volume":"51","year":"2004","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Haller, M.I., and Khuri-Yakub, B.T. (1993). Tapered acoustic matching layers. Proc. IEEE Ultrason. Symp., 505\u2013508.","DOI":"10.1109\/ULTSYM.1993.339558"},{"key":"ref_18","first-page":"235","article-title":"Review: Commercialization of piezoelectric single crystals for medical imaging applications","volume":"1","author":"Chen","year":"2005","journal-title":"Proc. IEEE Ultrason. Symp."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1016\/j.pmatsci.2014.06.001","article-title":"Piezoelectric single crystal ultrasonic transducers for biomedical applications","volume":"66","author":"Zhou","year":"2014","journal-title":"Prog. Mater. Sci."},{"key":"ref_20","first-page":"227","article-title":"Single crystal vs PZT ceramics for medical ultrasound applications","volume":"1","author":"Lu","year":"2005","journal-title":"Proc. IEEE Ultrason. Symp."},{"key":"ref_21","first-page":"969","article-title":"Single crystal transducers for medical imaging applications","volume":"2","author":"Gururaja","year":"1999","journal-title":"Proc. IEEE Ultrason. Symp."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"120","DOI":"10.1080\/00150193.2010.485546","article-title":"High frequency PMN\u2013PT 1-3 composite transducer for ultrasonic imaging application","volume":"408","author":"Sun","year":"2010","journal-title":"Ferroelectrics"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"477","DOI":"10.1109\/TUFFC.2011.1825","article-title":"Fabrication and performance of endoscopic ultrasound radial arrays based on PMN-PT single crystal\/epoxy 1-3 composite","volume":"58","author":"Zhou","year":"2011","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1016\/j.ultras.2012.06.017","article-title":"High frequency PMN\u2013PT single crystal focusing transducer fabricated by a mechanical dimpling technique","volume":"53","author":"Chen","year":"2013","journal-title":"Ultrasonics"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1016\/j.sna.2015.08.017","article-title":"Design and fabrication of relaxor-ferroelectric single crystal PIN\u2013PMN\u2013PT\/epoxy 2\u20132 composite based array transducer","volume":"234","author":"Yue","year":"2015","journal-title":"Sens. Actuators A"},{"key":"ref_26","unstructured":"Zhu, J. (2008). Optimization of Matching Layer Design for Medical Ultrasonic Transducer, The Pennsylvania State University."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"13543","DOI":"10.3390\/s131013543","article-title":"A Spherically-Shaped PZT Thin Film Ultrasonic Transducer with an Acoustic Impedance Gradient Matching Layer Based on a Micromachined Periodically Structured Flexible Substrate","volume":"13","author":"Feng","year":"2013","journal-title":"Sensors"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"42863","DOI":"10.1038\/srep42863","article-title":"Broadband gradient impedance matching using an acoustic metamaterial for ultrasonic transducers","volume":"7","author":"Li","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"074106","DOI":"10.1063\/1.4792661","article-title":"Complete set of elastic, dielectric, and piezoelectric constants of [011](C) poled rhombohedral Pb(In0.5Nb0.5)O3-Pb(Mg1\/3Nb2\/3)O3-PbTiO3: Mn single crystals","volume":"113","author":"Huo","year":"2013","journal-title":"J. Appl. Phys."},{"key":"ref_30","first-page":"7101","article-title":"Temperature dependence of electric-field-induced domain switching in 0.7Pb(Mg1\/3Nb2\/3)O3-0.3PbTiO3 single crystal","volume":"52","author":"Wang","year":"2012","journal-title":"J. Allo. Comp."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"429","DOI":"10.1007\/s10853-011-5816-x","article-title":"Dielectric and elastic properties of 0.70Pb(Mg1\/3Nb2\/3)O3\u20130.30PbTiO3 single crystal and their electric-field dependence","volume":"47","author":"Wang","year":"2011","journal-title":"J. Mater. Sci."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"024302","DOI":"10.1088\/0256-307X\/29\/2\/024302","article-title":"Surface Acoustic Wave Propagation in Relaxor-Based Ferroelectric Single Crystals 0.93Pb(Zn1\/3Nb2\/3)O3-0.07PbTiO(3) Poled along [011](c)","volume":"29","author":"Li","year":"2012","journal-title":"Chin. Phys. Lett."},{"key":"ref_33","first-page":"240","article-title":"Theoretical and numerical simulation of broadband transducer with gradient matching layers","volume":"40","author":"Li","year":"2018","journal-title":"Piezoelectrics Acoustoopt."},{"key":"ref_34","unstructured":"Zhu, K. (2015). The Study on the Acoustic Gradient Impedance Matching Layer of Ultransonic Transducer, Harbin Institute of Technology."},{"key":"ref_35","first-page":"1458","article-title":"Acoustic characteristics of the media with gradient change of impedance","volume":"35","author":"Yang","year":"2014","journal-title":"J. Harbin Eng. Univ."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"792","DOI":"10.1109\/58.852060","article-title":"Single crystal PZN\/PT-polymer composites for ultrasound transducer applications","volume":"47","author":"Ritter","year":"2000","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"790","DOI":"10.1016\/j.ultras.2010.04.001","article-title":"\u201cFabrication and comparison of PMN-PT single crystal, PZT and PZT-based 1\u20133 composite ultrasonic transducers for NDE applications\u201d","volume":"50","author":"Kim","year":"2010","journal-title":"Ultrasonics"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"084119","DOI":"10.1063\/1.2903456","article-title":"Preparation and electrical properties of fine-scale 1\u20133 lead zirconic titanate\u2215epoxy composite thick films for high-frequency ultrasonic transducers","volume":"103","author":"Zhen","year":"2008","journal-title":"J. Appl. Phys."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"107789","DOI":"10.1016\/j.apacoust.2020.107789","article-title":"Ultra-wideband underwater acoustic transducer with a gradient impedance matching layer","volume":"175","author":"Bian","year":"2021","journal-title":"Appl. Acoust."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Zhu, K., Ma, J., Liu, Y., Shen, B., Huo, D., Yang, Y., Qi, X., Sun, E., and Zhang, R. (2022). Increasing Performances of 1\u20133 Piezocomposite Ultrasonic Transducer by Alternating Current Poling Method. Micromachines, 13.","DOI":"10.3390\/mi13101715"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"936","DOI":"10.1093\/imamat\/hxn030","article-title":"Enhancing the performance of piezoelectric ultrasound transducers by the use of multiple matching layers","volume":"73","author":"Mulholland","year":"2008","journal-title":"IMA J. Appl. Math."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1016\/j.sna.2012.12.020","article-title":"Cylindrically shaped ultrasonic linear array fabricated using PIMNT\/epoxy 1-3 piezoelectric composite","volume":"192","author":"Wang","year":"2013","journal-title":"Sensors Actuators A Phys."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/20\/8025\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:58:22Z","timestamp":1760144302000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/20\/8025"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,10,20]]},"references-count":42,"journal-issue":{"issue":"20","published-online":{"date-parts":[[2022,10]]}},"alternative-id":["s22208025"],"URL":"https:\/\/doi.org\/10.3390\/s22208025","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,10,20]]}}}