Nonplanar High-Frequency Wideband Ultrasonic Transducer Arrays

非平面高频宽带超声波换能器阵列

• 批准号: 8824220
• 负责人: Omer Oralkan
• 金额: $ 6.93万
• 依托单位: NORTH CAROLINA STATE UNIVERSITY RALEIGH
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8824220
• 关键词: Acoustics; Adoption; Animals; Area; Cardiovascular system; Clinical; Coupling; Dermatology; Development; Diagnostic; Electric Capacitance; Electronics; Elements; Film; Frequencies; Geometry; Glass; Goals; Image; Individual; Industry; Lasers; Medicine; Methods; Microfabrication; Noise; Ophthalmology; Outcome; Output; Pattern; Penetration; Pilot Projects; Plasma; Polishes; Process; Resolution; Scanning; Shapes; Signal Transduction; Silicon; Solutions; Structure; Support System; Surface; System; Techniques; Technology; Testing; Thick; Time; Transducers; Ultrasonic Transducer; Ultrasonography; Width; Work; animal imaging; base; clinical application; comparative; cost; design; electric impedance; flexibility; imaging system; lens; novel; operation; pre-clinical; pressure; prevent; public health relevance; silicon nitride; simulation; submicron; tool; wasting

DESCRIPTION (provided by applicant): Technological difficulties associated with high-frequency (>20 MHz) transducer arrays have prevented wide adoption of high-resolution imaging systems for many decades. Recently, high-frequency arrays and a supporting system operating in the 20 - 70 MHz range have been commercially developed for small animal imaging. However, the extremely expensive cost of this system (>$500 k) and associated transducer probes (~$20 k) is still a huge barrier for widespread use of this preclinical tool as well as the expansion of array-based high-resolution imaging to clinical applications in ophthalmology, dermatology, and cardiovascular medicine. The major hurdles for the development of high-frequency arrays have been related to the conventional manufacturing techniques used for piezoelectric transducers: 1) The thickness of the piezoelectric crystal needs to be tens of microns for high-frequency operation. Using conventional techniques such as lapping and polishing it is very difficult to thin crystals down to required thicknesses. 2) The pitch of the array should be on the order of a wavelength (~50 m for 30 MHz). When the crystal is diced using a standard 10 to 15-�m blade, significant portion of the active area is wasted for element separation. Therefore, methods such as plasma etching or laser machining should be employed for dicing the crystal. 3) Depending on how the kerfs are filled, increased cross coupling could be observed between elements. 4) The small element size results in high electrical impedance and makes it more difficult to drive the array using external electronics. Capacitive micro machined ultrasonic transducer (CMUT) arrays have demonstrated over the last decade that they hold a great promise for the implementation of high-frequency arrays: 1) The frequency of operation of CMUTs is set by the width and thickness of a thin vibrating plate, which can be precisely defined with sub-micron features to enable efficient high-frequency transduction of ultrasound. 2) By lithographic patterning, densely placed array elements can be isolated from each other with no need for dicing. 3) It has been experimentally demonstrated that crosstalk in neighboring CMUT elements can be as low as -39 dB. 4) Electronic circuits can be conveniently integrated with transducer arrays on the same substrate or by chip-to-chip bonding to achieve a high signal quality, low noise, and wide bandwidth. CMUTs have the potential to further extend the frequency of operation, enable high-frequency 2-D arrays and arrays with other geometries, and lower the cost of array manufacture by taking advantage of batch microfabrication. To demonstrate high-frequency wideband elevation-focused CMUTs we have identified two specific aims: Specific Aim 1: Design, implement, and test 256-element, 1-D linear CMUT arrays operating at 40 MHz and 60 MHz center frequencies with a fractional bandwidth greater than 100%. Specific Aim 2: Develop a process to curve 1-D linear arrays on thin substrates in the elevation direction and demonstrate elevation focusing without using a glossy lens in front of the array.

描述（由申请人提供）：几十年来，与高频（>20 MHz）换能器阵列相关的技术困难一直阻碍着高分辨率成像系统的广泛采用。最近，在20 - 70 MHz范围内工作的高频阵列和支持系统已被商业开发用于小动物成像。然而，该系统（>$500 k）和相关换能器探头（~$20 k）的极其昂贵的成本仍然是该临床前工具的广泛使用以及基于阵列的高分辨率成像扩展到眼科学、皮肤病学和心血管医学中的临床应用的巨大障碍。开发高频阵列的主要障碍与用于压电换能器的传统制造技术有关：1）压电晶体的厚度需要为数十微米以用于高频操作。使用常规技术如研磨和抛光，很难将晶体薄化到所需的厚度。2)的 阵列的节距应该在波长的数量级上（对于30 MHz，约50 m）。当使用标准的10至15-μ m刀片切割晶体时，有效区域的大部分被浪费在元件分离上。因此，应该采用诸如等离子体蚀刻或激光加工的方法来切割晶体。3)取决于如何填充切口，可以观察到元件之间增加的交叉耦合。4)小的元件尺寸导致高电阻抗，并且使得使用外部电子器件驱动阵列更加困难。电容式微机械超声换能器（CMUT）阵列在过去十年中已经证明，它们在高频阵列的实现方面具有很大的前景：1）CMUT的操作频率由薄振动板的宽度和厚度设定，其可以精确地限定为具有亚微米特征，以实现超声的高效高频转换。2)通过光刻图案化，密集放置的阵列元件可以彼此隔离，而不需要切割。3)已经通过实验证明，相邻CMUT元件中的串扰可以低至-39dB。4)电子电路可以方便地与换能器阵列集成在同一基板上或通过芯片到芯片接合来实现高信号质量、低噪声和宽带宽。CMUT具有进一步扩展操作频率的潜力，能够实现高频2-D阵列和具有其他几何形状的阵列，并且通过利用批量微制造来降低阵列制造的成本。为了演示高频宽带仰角聚焦CMUT，我们确定了两个具体目标：具体目标1：设计、实现和测试256个单元的一维线性CMUT阵列，工作在40 MHz和60 MHz中心频率，部分带宽大于100%。具体目标二：开发一种工艺，在仰角方向上弯曲薄基板上的一维线性阵列，并演示在阵列前面不使用光泽透镜的仰角聚焦。