Microfabrication of a MEMS piezoresistive flow sensor - materials and processes

Microelectromechanical systems (MEMS) based artificial sensory hairs for flow sensing have been widely explored, but the processes involved in their fabrication are lithography intensive, making the process quite expensive and cumbersome. Most of these devices are also based on silicon MEMS, which makes the fabrication of out-of plane 3D flow sensors very challenging. This thesis aims to develop new fabrication technologies based on Polymer MEMS, with minimum dependence on lithography for the fabrication of piezoresistive 3D out-of-plane artificial sensory hairs for sensing of air flow. Moreover, the fabrication of a flexible sensor array is proposed and new materials are also explored for the sensing application. Soft lithography based approaches are first investigated for the fabrication of an all elastomer device that is tested in a bench top wind tunnel. Micromolding technologies allow for the mass fabrication of microstructures using a single, reusable mold master that is fabricated by SU-8 photolithography, reducing the need for repetitive processing. Polydimethylsiloxane (PDMS) is used as the device material and sputter deposited gold is used as both the piezoresistive as well as the electrode material for collection of device response. The fabrication results of PDMS to PDMS metal transfer micromolding (MTM) are shown and the limitations of the process are also discussed. A dissolving mold metal transfer micromolding process is then proposed and developed, which overcomes the limitations of the conventional MTM process pertinent to the present application. Testing results of devices fabricated using the dissolving mold process are discussed with emphasis on the role of micro-cr  acking as one failure mode in elastomeric devices with thin film metal electrodes. Finally, a laser microfabrication based approach using thin film Kapton as the device material and an electrically conductive carbon-black elastomer composite as the piezoresistor is proposed and demonstrated. Laminated sheets of thick and thin Kapton form the flexible substrate on which the conductive elastomer piezoresistors are stencil printed. Excimer laser ablation is used to make the micro-stencil as well as to release the Kapton cantilevers. The fluid-structure interaction is improved by the deposition of a thin film of silicon dioxide, which produces a stress-gradient induced curvature, strongly enhancing the device sensitivity. This new approach also enables the fabrication of backside interconnects, thereby addressing the commonly observed problem of flow intrusion while using conventional interconnection technologies like wire-bonding. Devices with varying dimensions of the sensing element are fabricated and the results presented, with smallest devices having a width of 400 microns and a length of 1.5 mm with flow sensitivities as high as 60 Ohms/m/s. Recommendations are also proposed for further optimization of the device.M.S.Committee Chair: Allen, Mark; Committee Member: Allen, Sue Ann Bidstrup; Committee Member: Wong, C.P

Secretion of fatty and albuminous yolk by Golgi bodies in Stomopneustes variolaris, Lamarck

1. The Golgi bodies in the oocytes of Stomopneustes secrete both fatty and albuminous yolk grains. 2. The Golgi vasicle enlarges into a vacuole inside which fatty yolk appears to be deposited. The Golgirim does not undergo any transformation. 3. Prior to secretion of albuminous yolk the mitochondria clump together. The Golgi vesicles by rupture give rise to scale or batonette like bodies. These attach themselves to the mitochondrial clumps and secrete albuminous yolk. The mitochondria in the fully developed yolk spheres are yolky. 4. The origin of both fatty and albuminous yolk in relation with the Golgi bodies only confirms the belief that the nature of the action of the apparatus is only by means of enzymes and that fat, fatty yolk and yolk are only secondary products resulting from the action of these enzymes on materials derived from mitochondria, cytoplasm, nucleolus, etc

Shark and shark-liver oil

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Reaction of chromium(VI) with glutathione or with hydrogen peroxide: identification of reactive intermediates and their role in chromium(VI)-induced DNA damage.

The types of reactive intermediates generated upon reduction of chromium(VI) by glutathione or hydrogen peroxide and the resulting DNA damage have been determined. In vitro, reaction of chromium(VI) with glutathione led to formation of two chromium(V) complexes and the glutathione thiyl radical. When chromium(VI) was reacted with DNA in the presence of glutathione, chromium-DNA adducts were obtained, with no DNA strand breakage. The level of chromium-DNA adduct formation correlated with chromium(V) formation. Reaction of chromium(VI) with hydrogen peroxide led to formation of hydroxyl radical. No chromium(V) was detectable at 24 degrees C (297 K); however, low levels of the tetraperoxochromium(V) complex were detected at 77 K. Reaction of chromium(VI) with DNA in the presence of hydrogen peroxide produced significant DNA strand breakage and the 8-hydroxydeoxyguanosine adduct, whose formation correlated with hydroxyl radical production. No significant chromium-DNA adduct formation was detected. Thus, the nature of chromium(VI)-induced DNA damage appears to be dependent on the reactive intermediates, i.e. chromium(V) or hydroxyl radical, produced during the reduction of chromium(VI)

Growth in some stomatopods

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On some squilla larvae from the Madras plankton

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The wellbeing and support experiences of parents and caregivers from South and Southeast Asian refugee backgrounds during the First 2000 Days: A systematic review

Available online 10 October 2023There is growing scholarly attention concerning the wellbeing experiences of people from refugee and asylumseeking backgrounds, particularly in relation to antenatal and postnatal care in countries of resettlement. However, less is known about early childhood support for refugee and asylum-seeking parents during the First 2000 Days of a child’s life (conception to age five). There is also little understanding of the needs of refugees and asylum-seekers from South and Southeast (S/SE) Asia for whom there may be unique cultural considerations regarding parenting and support. This systematic review therefore aimed to explore the emotional and physical wellbeing and support experiences of refugee and asylum-seeking families (mothers, fathers, and other family members with caregiving roles) from S/SE Asia during the First 2000 Days. This review was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We identified publications through a systematic search of six databases. Eligible papers were peer-reviewed, primary data studies published in English, conducted in middle- to high-income countries of resettlement, and included data that could be disaggregated for S/SE Asian families. Of 5,770 publications, 13 articles met inclusion criteria. While our review aimed to explore the experiences of various family members, included papers focused primarily on the experiences of refugee women. Our review found that S/SE Asian refugee parents reported various challenges to physical and emotional wellbeing during the First 2000 Days ranging from nutrition and diet concerns to feelings of anxiousness, grief, isolation, and feelings of distress in healthcare settings. Parents also expressed a level of trust and satisfaction with maternity care during resettlement, however, these experiences were challenged by a lack of culturally responsive care. Findings speak to the importance of informal social supports for S/SE Asian refugee parents, and culturally safe, formal supports where parents feel comfortable to voice their concerns.Ria Aiyar, Clemence Due, Amanda M. Taylor, Alyssa C.P. Sawye