Quantifying Dimensional Accuracy of a Mask Projection Micro Stereolithography System

Mask Projection Microstereolithography is capable for fabricating true three-dimensional microparts and hence, holds promise as a potential micro-fabrication process for micro-machine components. In this paper, the Mask Projection Micro-Stereolithography (MPµSLA) system developed at the Rapid Prototyping and Manufacturing Institute at Georgia Institute of Technology is presented. The dimensional accuracy of the system is improved by reducing its process planning errors. To this effect, the MPµSLA process is mathematically modeled. In this paper, the irradiance received by the resin surface is modeled as a function of the imaging system parameters and the pattern displayed on the dynamic mask. The resin used in the system is characterized to experimentally determine its working curve. This work enables us to compute the dimensions of a single layer cured using our system. The analytical model is validated by curing test layers on the system. The model computes layer dimensions within 5% error.Mechanical Engineerin

Process Planning to Build Mask Projection Stereolithography Parts with Accurate Vertical Dimensions

Mask Projection Stereolithography (MPSLA) is a high resolution manufacturing process that builds parts layer by layer in a photopolymer. In this paper, we formulate a process planning method to cure MPSLA parts with accurate vertical dimensions. To this effect, we have formulated and validated the “Layer cure” model that models the thickness of a cured layer as a transient phenomenon, in which, the thickness of the layer being cured increases continuously throughout the duration of exposure. We have shown that for longer durations of exposures, such as those common with MPSLA systems, cure depth varies linearly with exposure. We have also quantified the effect of diffusion of radicals on the cure depth when discrete exposure doses, as opposed to a single continuous exposure dose, are used to cure layers. Using this work, we have formulated and validated the “Print through” model that computes the extra curing that would occur when multiple layers are cured over each other. We have implemented the Print through model to simulate the profile of a down facing surface of a test part and validated the simulation result by building the test part on our MPSLA system.Mechanical Engineerin

Compensation Zone Approach to Avoid Z Errors in Mask Projection Stereolithography Builds

Print-through results in unwanted polymerization occurring beneath a part cured using Mask Projection Stereolithography (MPSLA) and thus creates error in its Z dimension. In this paper, the "Compensation zone approach" is proposed to avoid this error. This approach entails modifying the geometry of the part to be cured. A volume (Compensation zone) is subtracted from underneath the CAD model in order to compensate for the increase in the Z dimension that would occur due to Print-through. Three process variables have been identified: Thickness of Compensation zone, Thickness of every layer and Exposure distribution across every image used to cure a layer. Analytical relations have been formulated between these process variables in order to obtain dimensionally accurate parts. The Compensation zone approach is demonstrated on an example problem.Mechanical Engineerin

A study to determine the knowledge of pharmacovigilance among pharmacy students from Mumbai university

Background: Pharmacovigilance (PV); also known as drug safety surveillance, is the science of enhancing patient care and patient safety regarding the use of medicines by collecting, monitoring, assessing, and evaluating information from healthcare providers and patients. Pharmacists are pivotal players in adverse drug event (ADE) monitoring and reporting. However, most pharmacists are unaware or not knowledgeable about the guidelines used by their respective countries’ drug regulatory bodies. It is the need of the hour to train pharmacy students on the concept of pharmacovigilance.Methods: A cross-sectional study was carried out among pharmacy students from Mumbai University, India during May-June 2017. On the basis of the eligibility criterion 352 students were selected for the present study. Four hundred students were approached to participate in the study of which 201 agreed to participate (males: 179; females: 173). Pretested questionnaire was distributed and collected data was analyzed using IBM SPSS version 23.Results: Overall pharmacovigilance knowledge (44%) and perception (58%) was low among the participants of the present study. Seventy four percent of the participants felt that adverse drug reaction (ADR) reporting should be made compulsory for healthcare professionals. And only 21% agreed that the topic of Pharmacovigilance is well covered in pharmacy curriculum.Conclusions: Pharmacy council of India, pharmacy teacher’s association and respective pharmacy college should take necessary steps to increase the knowledge and create awareness regarding pharmacovigilance and adverse drug reaction reporting among pharmacy students.

Multi-objective process planning method for Mask Projection Stereolithography

Mask Projection Stereolithography (MPSLA) is a high resolution manufacturing process that builds parts layer by layer in a photopolymer. In this research, a process planning method to fabricate MPSLA parts with constraints on dimensions, surface finish and build time is formulated. As a part of this dissertation, a MPSLA system is designed and assembled. The irradiance incident on the resin surface when a given bitmap is imaged onto it is modeled as the Irradiance model . This model is used to formulate the Bitmap generation method which generates the bitmap to be imaged onto the resin in order to cure the required layer. Print-through errors occur in multi-layered builds because of radiation penetrating beyond the intended thickness of a layer, causing unwanted curing. In this research, the print through errors are modeled in terms of the process parameters used to build a multi layered part. To this effect, the Transient layer cure model is formulated, that models the curing of a layer as a transient phenomenon, in which, the rate of radiation attenuation changes continuously during exposure. In addition, the effect of diffusion of radicals and oxygen on the cure depth when discrete exposure doses, as opposed to a single continuous exposure dose, are used to cure layers is quantified. The print through model is used to formulate a process planning method to cure multi-layered parts with accurate vertical dimensions. This method is demonstrated by building a test part on the MPSLA system realized as a part of this research. A method to improve the surface finish of down facing surfaces by modulating the exposure supplied at the edges of layers cured is formulated and demonstrated on a test part. The models formulated and validated in this dissertation are used to formulate a process planning method to build MPSLA parts with constraints on dimensions, surface finish and build time. The process planning method is demonstrated by means of a case study.Ph.D.Committee Chair: Rosen David; Committee Member: Adibi Ali; Committee Member: Henderson Clifford; Committee Member: Lu Jye-Chyi; Committee Member: Melkote Shreyes; Committee Member: Paredis Christiaa

Design and Analysis of a Mask projection Micro Stereolithography System

Mask Projection Microstereolithography (MPSLA) is an additive manufacturing process capable for fabricating true three-dimensional microparts and hence, holds promise as a potential micro-fabrication process for micro-machine components. With only a few MPSLA systems developed and studied so far, the research in this field is inchoate and experimental in nature. The process of curing a micropart using an MPSLA system has not been analytically modeled and no literature on process planning for MPSLA is available. In order to employ the MPSLA technology for microfabrication, it is necessary to model its part building process and formulate a process planning method to cure dimensionally accurate microparts. As a part of this thesis, an MPSLA system is designed and assembled. The process of curing a single layer using this system is analytically modeled as the Layer cure model. The Layer cure model is formulated in two steps. First, the irradiance received by the resin surface is modeled as a function of the system parameters (Irradiance model). Then, the resin used in the system is characterized to experimentally determine its working curve. The Irradiance model and the resin characterization enable us to compute the dimensions of any layer cured using our MPSLA system in terms of the process parameters. The Layer cure model has been validated by curing test layers on our system. Finally, the Layer cure model has been inverted to formulate a process planning method to cure layers of the required dimensions. Using this process planning method, it is possible to cure layers within a dimensional error of 3%.M.S.Committee Chair: Dr. David W. Rosen; Committee Member: Dr. Ali Adibi; Committee Member: Dr. Peter J. Hesket

SRL Research Overview - Rosen's Students

Presentation given for SRL meeting Summer 200

A study to determine the knowledge of pharmacovigilance among pharmacy students from Mumbai university

Background: Pharmacovigilance (PV); also known as drug safety surveillance, is the science of enhancing patient care and patient safety regarding the use of medicines by collecting, monitoring, assessing, and evaluating information from healthcare providers and patients. Pharmacists are pivotal players in adverse drug event (ADE) monitoring and reporting. However, most pharmacists are unaware or not knowledgeable about the guidelines used by their respective countries’ drug regulatory bodies. It is the need of the hour to train pharmacy students on the concept of pharmacovigilance. Methods: A cross-sectional study was carried out among pharmacy students from Mumbai University, India during May-June 2017. On the basis of the eligibility criterion 352 students were selected for the present study. Four hundred students were approached to participate in the study of which 201 agreed to participate (males: 179; females: 173). Pretested questionnaire was distributed and collected data was analyzed using IBM SPSS version 23. Results: Overall pharmacovigilance knowledge (44%) and perception (58%) was low among the participants of the present study. Seventy four percent of the participants felt that adverse drug reaction (ADR) reporting should be made compulsory for healthcare professionals. And only 21% agreed that the topic of Pharmacovigilance is well covered in pharmacy curriculum. Conclusions: Pharmacy council of India, pharmacy teacher’s association and respective pharmacy college should take necessary steps to increase the knowledge and create awareness regarding pharmacovigilance and adverse drug reaction reporting among pharmacy students

A Stapled Peptide Mimic of the Pseudosubstrate Inhibitor PKI Inhibits Protein Kinase A

Kinases regulate multiple and diverse signaling pathways and misregulation is implicated in a multitude of diseases. Although significant efforts have been put forth to develop kinase-specific inhibitors, specificity remains a challenge. As an alternative to catalytic inhibition, allosteric inhibitors can target areas on the surface of an enzyme, thereby providing additional target diversity. Using cAMP-dependent protein kinase A (PKA) as a model system, we sought to develop a hydrocarbon-stapled peptide targeting the pseudosubstrate domain of the kinase. A library of peptides was designed from a Protein Kinase Inhibitor (PKI), a naturally encoded protein that serves as a pseudosubstrate inhibitor for PKA. The binding properties of these peptide analogs were characterized by fluorescence polarization and surface plasmon resonance, and two compounds were identified with KD values in the 500–600 pM range. In kinase activity assays, both compounds demonstrated inhibition with 25–35 nM IC50 values. They were also found to permeate cells and localize within the cytoplasm and inhibited PKA activity within the cellular environment. To the best of our knowledge, these stapled peptide inhibitors represent some of the highest affinity binders reported to date for hydrocarbon stapled peptides