Jose Joseph

Fabrication of SU-8 based Capacitive Micromachined Ultrasonic Transducer for low frequency therapeutic applications

In this paper we present a simple post-CMOS compatible sacrificial release method of fabricating SU-8 based Capacitive Micromachined Ultrasonic Transducer (CMUT) for low frequency therapeutic applications. CMUTs fabricated with Silicon Nitride and Silicon Dioxide lay constraints in terms of area and power consumption especially in the low frequency range. Fabrication of these devices need complex high temperature processes that makes them incompatible for post-CMOS processing. Analytical modeling shows that SU-8 based CMUT consumes less area (below 25%) and power compared to Silicon Nitride and Silicon Dioxide based CMUTs. The proposed fabrication method overcomes inherent disadvantages of sacrificial release method by providing uniformity in air gap and reducing the possibility of stiction.

A low pull-in SU-8 based Capacitive Micromachined Ultrasonic Transducer for medical imaging applications.

In this paper we present a thorough analysis of a low pull-in voltage Capacitive Micromachined Ultrasonic Transducer (CMUT) using SU-8 as the membrane material. It is designed to operate at 1 MHz frequency that has a wide range of applications including the imaging of deeper organs. We also propose a simple state-of-the-art fabrication methodology for the same. As compared to the standard Silicon Nitride CMUTs, the proposed structure gives the same electromechanical coupling coefficient with lower membrane dimensions and low pull-in voltage which in turn results in reduced area and power consumption. Moreover the proposed fabrication methodology is a low temperature process which makes it CMOS compatible.

Leveraging Innate Piezoelectricity of Ultra-Smooth Silk Thin Films for Flexible and Wearable Sensor Applications

In this paper, the innate peizoelectricity of silk is utilized to demonstrate an optimized silk thin film-based pressure sensor. Furthermore, a novel approach to pattern silk films is proposed, which could potentially lead to the development of a variety of miniaturized, flexible, and wearable sensors. The key in this endeavor is to achieve a uniform thin film of silk. The preparation methodology was optimized to achieve an ultra-smooth, reproducible thin film. The surface quality of the optimized thin film was analyzed using atomic force microscopy and the RMS roughness was found to be 2.43 nm. The piezo-response of the silk film was measured using Piezo force microscopy and the average

Silk piezoelectric thin films: Materials to devices

d_{33}

A low power, area efficient fpga based beamforming technique for 1-D CMUT arrays.

value of the silk piezoelectric thin film was estimated at 56.7 pm/V. A pressure sensor using silk piezoelectric thin film was developed with a simple process flow. This process is devoid of any silk patterning steps. Keeping in view the potentiality of piezoelectric silk films in MEMS, a novel lithography-based technique was developed to pattern the silk films. This patterning technique can easily be integrated with any standard MEMS/Post CMOS process flow, thus opening up a new avenue in developing a variety of sensors.

Flexible ITO Electrode With Gold Nanostructures for Femtomolar DNA Hybridization Detection

In this paper, we present the preparation and characterization of silk piezoelectric thin films for biomedical applications. The silk thin films were prepared in formic acid medium. Drying condition to achieve a uniform, stress free thin film was optimized. Atomic Force Microscopy was employed to analyze the surface quality of the as prepared thin film. The RMS roughness of the silk thin film was found to be 2.43 nm. The piezo-response of the silk films was measured using Piezo Force Microscopy and the average d33 value of the silk piezoelectric thin film was found to be 56.7 pm/V. A novel lithography based technique was developed to pattern the silk films. We believe this breakthrough will be a stepping stone for realizing silk based wearable biomedical devices.

alternative Materials/Approaches to Develop Miniaturized Ultrasonic Transducers-A Device

A low power area efficient digital beamformer targeting low frequency (2MHz) 1-D linear Capacitive Micromachined Ultrasonic Transducer (CMUT) array is developed. While designing the beamforming logic, the symmetry of the CMUT array is well exploited to reduce the area and power consumption. The proposed method is verified in Matlab by clocking an Arbitrary Waveform Generator(AWG). The architecture is successfully implemented in Xilinx Spartan 3E FPGA kit to check its functionality. The beamforming logic is implemented for 8, 16, 32, and 64 element CMUTs targeting Application Specific Integrated Circuit (ASIC) platform at Vdd 1.62V for UMC 90nm technology. It is observed that the proposed architecture consumes significantly lesser power and area (1.2895 mW power and 47134.4 μm2 area for a 64 element digital beamforming circuit) compared to the conventional square root based algorithm.