This Small Business Innovation Research (SBIR) Phase II project aims to develop high dielectric constant (high-K) thick film for high-frequency ultrasonic transducer. Thick piezoelectric film technology is very attractive for the fabrication of thin piezoelectric element in high-frequency ultrasonic medical imaging applications. However, it is challenging to process high-quality piezoelectric film with thickness in the range of 10-20 micrometers. In addition, the film needs to demonstrate dielectric constant of 3000 or higher due to the need of electric matching in fabricating array transducers. In previous Phase I project, a piezoelectric thick film with dielectric constant higher than 3000 was demonstrated. In this Phase II project, the high-K thick film will be utilized to develop miniature high frequency single element and linear array transducers for Intravascular Ultrasonic (IVUS) imaging applications.
The broader/commercial impact of this project will be the potential to provide high-K thick film to enable the application of miniature high-frequency ultrasonic transducers. IVUS is a medical imaging methodology using a specially designed catheter with a miniaturized ultrasound probe attached to the distal end of the catheter, which is inserted into the heart or into a coronary vessel for visualizing the vessel and heart structure. This project is expected to further miniaturize the ultrasonic transducer mounted on the catheter and provide improved resolution. With this anticipated catheter, surgeons may view the arteries of patients more clearly and spend less surgery time. Plus, the smaller size will make the procedure less invasive. In addition, this technology can also be used in other applications such as Radio Frequency (RF) filters for cell phone, ultrasonic valve and tuning devices, liquid delivery and droplet ejectors, chemical and biomedical sensors etc.
More than 2,000,000 people a year who suffer from heart disease undergo some sort of diagnostic procedure or bypass surgery where the surgeon uses digital images to see within the heart's interior arteries. X-ray angiography is the current gold standard used in 90% of US hospitals for vessel characterization and diagnosis of aneurysm, stroke and cardiac and peripheral blood vessel disease. Though this technique helps guide catheters to a desired spot in a vessel, it has several limitations. X-ray angiography is a 2D-technique and do not provide critical 3D and cross-sectional details necessary for identifying early vulnerable plaques. Also, very poor resolution in X-ray angiograms makes it very difficult to detect critical less obtrusive vulnerable plaques. Therefore, new imaging techniques with high resolution are needed to assess plaque prognosis. The major (86%) cause of cardiovascular death in heart attacks and the major cause of (45%) deaths from brain aneurysm are due to less obtrusive plaques also known as "vulnerable plaques" that rupture suddenly, triggering a blood clot or thrombus that blocks blood flow. For successful diagnosis, early detection of "vulnerable plaques" is very important which occur at a length scale of 20 microns -150 microns. Therefore, medical imaging technique is desirable to have a resolution of close to 20 microns. It is the goal of this project to develop one of key parts of such high resolution imaging system. High frequency ultrasonic imaging (HFUI) is a new frontier in diagnostic ultrasound. High frequency ultrasound has been used for various applications in ophthalmology, dermatology, superficial organ imaging, intravascular (IVUS) imaging, small organs and small animal studies as a diagnostic tool and as a surgical guidance tool. The project is to develop miniaturer transducer for higher resolution ultrasound medical imaging with high resolution. During this project, Chemat in collaboration with Resource Center for Medical Ultrasonic Imaging Transducer Technology at University of Southern California has addressed numbers of technical challenges on how to fabricate miniature transducer. At high frequency of >60MHz, the feature of transducer becomes very small (about 1/10 of human hair). It is therefore difficult to fabricate with conventional processing technique in a cost effective manner. We have developed a bottom-up process to replace conventional top-down process via sol-gel process. We have successfully developed prototype of high frequency (f>60MHz) single element and linear array high frequency transducers. Techniques developed in this project include: Ceramic film with thickness of 10 to 40 micrometer via bottom-up process: 1) sol-gel spin-on coating process; 2) tape-casting process. Micro-kerf fabrication via dry etching and lift-off Piezoelectric single element and array transducer fabrication Sol-gel solution and powder synthesis
