Doctor of Philosophy

dissertationTactile sensors are a group of sensors that are widely being developed for transduction of touch, force and pressure in the field of robotics, contact sensing and gait analysis. These sensors are employed to measure and register interactions between contact surfaces and the surrounding environment. Since these sensors have gained usage in the field of robotics and gait analysis, there is a need for these sensors to be ultra flexible, highly reliable and capable of measuring pressure and two-axial shear simultaneously. The sensors that are currently available are not capable of achieving all the aforementioned qualities. The goal of this work is to design and develop such a flexible tactile sensor array based on a capacitive sensing scheme and we call it the flexible tactile imager (FTI). The developed design can be easily multiplexed into a high-density array of 676 multi-fingered capacitors that are capable of measuring pressure and two-axial shear simultaneously while maintaining sensor flexibility and reliability. The sensitivity of normal and shear stress for the FTI are 0.74/MPa and 79.5/GPa, respectively, and the resolvable displacement and velocity are as low as 60 µm and 100 µm/s, respectively. The developed FTI demonstrates the ability to detect pressure and shear contours of objects rolling on top of it and capability to measure microdisplacement and microvelocities that are desirable during gait analysis

A very high density floating electrode flexible sensor array for high-resolution measurements of contact forces

pre-printWe present the development, fabrication and testing results of a new high-density flexible sensor array (HDFA) suitable of recording three-axis stresses with high spatial resolution. The new HDFA consists of 676 (26×26) sensing cells fabricated on top of a high-density flex circuit substrate. Each sensing cell is implemented using four floating comb electrodes separated from the flex substrate by a thin layer of a compressible PDMS film. Each sensing cell measures 2.77×2.55 mm2 thus packing 2704 capacitors in an area of ~ 50 cm2. The HDFA is read using a high-speed switched-capacitor circuit with a 13-bit resolution at full frame rates of 100 Hz (~0.8Mb/s). The new array is capable of detecting contact line displacements as low as 35 μm and contact line velocities as low as 38 μm/s

A high-resolution flexible tactile imager system based on floating comb electrodes

pre-printFlexible high-resolution contact force imagers are needed in many applications for robotic grippers and gait analysis, but its intrinsic intimate contact requirement often causes breaking of top metallization layers and failure in a short time. The use of floating electrodes has significantly improved the reliability of traditional quad-cell capacitive tactile sensing devices. In this paper we present a new type of high-resolution (676-sensors) flexible pressure/shear imager array based on floating combs. Each sensing cell consists of two sets of orthogonal comb electrodes connected in a differential capacitance configuration. The shear sense direction (+x, -x, +y, -y) is determined by the amount of asymmetric comb overlap. Pressure readouts are obtained from the net capacitance of the cell. The new comb configuration multiplies the shear capacitive signal by the number of combs per cell. The imager is read using a high-speed switched-capacitor circuit with a 12-bit resolution at full frame rates of 100 Hz (~ 0.8Mb/s)

MS

thesisA genomic DNA (gDNA) extraction and quantification system using flow rate analysis was designed and fabricated using a nanoporous membrane-embedded microfluidic system. A nanoporous aluminum oxide membrane was embedded in a microfluidic system that was fabricated using a PDMS/tape composite. To prove the concept of the system, 370nm nanoparticles were used and extracted on a membrane with 200nm pores. As nanoparticles collect on the membrane, the flow rate initially decreases linearly before switching to an exponential decrease. In a similar manner, a gDNA sample was flowed and trapped on the membrane and the measured flow rate change was used to evaluate the mass of gDNA on the membrane. After preliminary testing, gDNA of 6.25ng/(al, 12.5ng/ul, 18.75ng/|ul and 25ng/^l concentrations were extracted over 20nm pore sized membranes and a similar flow rate profile was observed. As the amount of gDNA trapped on the membrane increases, the pressure drop in the microfluidic system increases. Using the experimental data, one can develop an empirical formula for the mass of gDNA collected and the concentration of gDNA in the sample. From this empirical equation, it is possible to estimate the gDNA sample concentration from the measured flow rate change caused by an unknown sample. By integrating this system with a microfluidic gDNA sample preparation system, we not only extract gDNA, but also quantify the mass of gDNA collected, which allows for operators to end tests that will clearly be negative or allows operators to extend the extraction process until sufficient nucleic acid material is obtained

A study on association and correlation of lip and finger print pattern analysis for gender identification

Background: The lip print pattern is a unique among individuals and thus helps in the identification during the forensic investigation. Lip print analysis in the forensic scene may help in the personal identification. Thus, correlating the lip print with the finger print and gender will create a new room in forensic dentistry investigation. Aim: This study aims to identify the lip and finger print pattern and to correlate lip and finger print pattern for gender identification. Materials and Methods: A total of 100 students from dental institution were included in this study. Of which, 50 were male and 50 were female.. Their aged range between 18 and 28 years with a mean age of 21.3 years. The physiological rest position of the lip print was recorded by the application of red or dark pink colored lipstick over the lips and the imprint was transferred over a white chart sheet through a transparent tape. The imprint of the finger was taken directly on a white chart sheet. The lip and finger print pattern was examined with magnifying lens. The results were analyzed using SPSS software 19.0 (Armonk, NY, USA) and presented as a descriptive statistics. A correlation of lip print with finger print and gender variation was analyzed by Pearson correlation test. Results: The study identified higher prevalence of Type II (34%) lip print pattern in the overall study population. In males, Type I lip print (42%) and plain loop finger print pattern (44%) was frequent in the study. In males, the correlation of lip and finger print patter showed weaker correlation and statistically insignificant (P = 0.436). In females, Type II lip print (34%) and plain loop finger print pattern (42%) was frequent in the study. In females, the correlation of the lip and finger print pattern showed weaker correlation with approachable statistical significance (P = 0.083). The correlation of lip and finger print with gender showed weaker correlation and approachable significance (P = 0.07). The association of lip and finger print in the study showed statistically insignificant. However, the association of Type III lip print pattern with loop finger print pattern showed statistical significant association (P = 0.05) by Chi-square analysis. Conclusion: Lip print analysis is a challenging area in the personal identification during forensic dentistry examination. The study revealed the weaker correlation and approachable significance of lip and finger print pattern in gender identification. Future studies should be encouraged in the direction of software based identification for lip and finger print analysis in gender identification. Such studies may benefit this study pattern in more accurate way

Pituitary Stalk Duplication: A Radiological Surprise in a Child With Short Stature

Objective: Pituitary stalk abnormalities are one of the causes of hypopituitarism. Isolated pituitary stalk duplication with a single pituitary gland is extremely rare with only a few cases reported to date. The present case has a different clinical picture as compared to the cases that were previously reported in the literature. Case Report: A 2 years 6-month-old male child, a product of nonconsanguineous marriage, presented with short stature, micropenis with unilateral undescended testis, and delayed motor milestones. His bone age was delayed by 6 months. On further evaluation, he was found to be euthyroid, with stimulated growth hormone (GH) and stimulated gonadotropin levels were suboptimal, whereas the cortisol and the prolactin were normal. Magnetic resonance imaging of the pituitary revealed pituitary stalk duplication with a single pituitary gland of normal dimensions and fused tuber cinereum and mammillary body. Discussion: To our knowledge, only 7 cases with isolated pituitary stalk duplication were reported. The presenting complaint could be primarily of hypopituitarism like short stature or a neurologic complaint or ocular abnormality. The pituitary hormone deficiencies are variable with GH deficiency being the most common as seen in our case. Other associated features could be the morning glory disc anomaly, moyamoya disease, pituitary adenoma or hypoplasia, split hypothalamus, and sellar dermoid. Conclusion: Pituitary stalk duplication is a developmental disorder that is diagnosed only by imaging. Patients should be evaluated for hypopituitarism, particularly the GH and gonadotrophins deficiency, and also screened for associated neurologic and ocular abnormalities