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Polyjet printing, a multi-jet Additive Manufacturing technique, has been used to fabricate 3-Dimensional structures for various polymeric material systems. This technique uses a layer-by-layer deposition method and allows for the fabrication of parts with different material compositions and varying thermomechanical properties. The current research investigates the influence of process-induced variation on Mode 1(K1C) fracture toughness of the Vero material system. Compact Tension (C-T) specimens with crack fronts parallel and perpendicular to the print direction were fabricated. The orientation of the crack front relative to the print and build directions influenced the Mode I fracture toughness values. When the crack front was parallel to the print plane, K1C decreased by 49.54%, G1C decreased by 41.56%, and peak load intensity decreased by 52.76% compared to the perpendicular crack front orientation. C-T samples were modeled in CAD to correlate with the experimental results and then analyzed in the Ansys workbench. The FEA yielded a Mode 1 fracture toughness value of 2.48 MPa m0.5 for a perpendicular configuration of the crack front and a fracture toughness value of 1.15 MPa m0.5 for a parallel configuration of the crack front. The Representative Volume Element method is used for a composite containing the Vero material system as a matrix and carbon nanofibers as reinforcement. Carbon nanofibers are integrated using a customized material configuration, and their influence on fracture is studied. A tailored network perpendicular to the crack front in a 3D printed C-T specimen stiffens the specimen. In contrast, a tailored network parallel to the crack front has a relaxing impact, indicating that an additively created part may be prone to softening under certain conditions.

Selective Laser Melting (SLM) is an up-and-coming additive manufacturing technique that uses a laser as the power source and is specially developed for 3D Printing metal alloys. SLM advancement is significant since it can create custom property parts, reduce material usage and design freedom, and quickly manufacture complex components. The high energy density of laser generates various unwanted structural defects such as keyholes and porosity, which results in crack formation & distortion, and subsequent reduction in mechanical strength of the components. The present work aims to simulate the relevant physical configurations of the SLM process and identify process parameters and the effect of metal powder variation. A representative model based on Molecular Dynamics (MD) is developed to explore the sintering mechanism of metal powders. Open-source code LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) has been used to develop a working model to emulate a powder bed consisting of metal particles. The melting phenomenon is simulated by the heating layer of the metal particle bed. The results from this study will be able to predict the onset mechanism of porosity better and crack formation in Metal 3D printed parts.

The purpose of this study is to develop a novel bone replacement using in situ polymerization of thiol-acrylate with adipose tissue derived adult stem cells (ASCs). Specifically, Poly(ethylene glycol) diacrylate-co-trimethylolpropane tris (3-mercaptopropionate) (PEGDA-co-TMPTMP) was synthesized with 10% Hydroxyapatite (HA) foam by an amine-catalyzed Michael addition reaction. Initial characterization studies were performed to determine the temperature profile during the exothermic reaction showing a peak temperature of 50°C. To prevent hyperthermic cell damage and death during the exothermic polymerization procedure, the hASCs were encapsulated in alginate. Characterization of the 3-D structure and interconnectivity of pores in the polymeric foam scaffolds were performed using FIB-SEM and Micro-CT showing uniform distribution of HA. Cell viability experiments within the polymeric scaffold were performed using Vybrant® MTT cell profileration method, as well as fluorescent dyes: Calcein-AM (live) and Ethidium homodimer-1 (dead) showing viability of cells inside the samples.Copyright © 2015 by ASME

Poly (l-lactic acid) (PLLA) scaffolds for bone grafts were prepared by using Thermally Induced Phase Separation (TIPS) method. Solutions of PLLA-dioxane was formed by dissolving a pre-determined value of PLLA in dioxane (3, 7 and 10% wt/vol) at 323K. These solutions were frozen at controlled cooling rates (1, 10 and 40°C/min) in cylindrical capsules. The frozen solutions were freeze-dried for a period of 48 hours for the frozen dioxane to completely sublimate, leaving the porous PLLA scaffold. The scaffolds which were formed under different processing conditions were characterized in terms of porosity, pore sizes and compressive moduli.Copyright © 2013 by ASME

Bio-degradable poly (l-lactic acid) (PLLA) scaffolds were prepared by using thermally induced phase separation (TIPS) method. A solution of PLLA-Dioxane was formed by dissolving PLLA in dehydrated 1,4-Dioxane at three wt/vol percentages, specifically 3, 7 and 10%. This PLLA-Dioxane solution was then frozen in borosilicate glass vials (5mL) at three cooling rates (1, 10 and 40 °C/min) in a commercially available controlled rate freezer (CRF). The frozen solution was freeze-dried to sublimate the dioxane. The microstructural properties of the resulting PLLA scaffolds were determined utilizing Scanning Electron Microscopy (SEM) images and uniaxial compressive testing. The relationship between the wt/vol ratio of PLLA and Dioxane and the imposed cooling rates on the structural properties of PLLA scaffolds was determined.Copyright © 2012 by ASME

Dr. Diller is undoubtedly one of most important researcher in the field of bioheat and mass transfer as it applies to low temperature biology over the last 40 odd years. This talk will highlight his seminal contributions to the field.Copyright © 2012 by ASME

Bio-degradable Poly (l-lactic acid) (PLLA) scaffolds were prepared by using thermal liquid-liquid phase separation method. A solution of PLLA-Dioxane was prepared by dissolving PLLA in dehydrated 1,4-Dioxane. This PLLA-Dioxane solution was then directionally frozen in vials of similar dimensions but made of different materials (borosilicate glass, aluminum and copper). The frozen solution was then placed in a freeze-dryer to allow for the frozen dioxane to sublimate or lyophilized. The porosities of the resulting PLLA scaffolds were calculated and their porous structures were studied and compared between the three different vials (and the corresponding cooling rates).Copyright © 2012 by ASME

A two-step directional freezing method was utilized to assess the membrane integrity in frozen/thawed adult stem cells (ASCs). Using a custom built directional solidification stage (DSS) we determined that cells cooled at two different rates (i.e., a slower rate between room temperature, 27 °C and −10 °C and a higher rate between −10 °C and −60 °C) experienced significantly higher loss of cell viability when compared with those cooled at a single and uniform slower cooling rate between 27 °C and −60 °C. Specifically, the cells cooled using the two-step freezing method exhibited a post-thaw cell viability of ∼17% while those that were cooled using the traditional method exhibited a cell viability of 49%. We also found that varying the cooling rate between 27 °C and −10 °C did not significantly affect the post-thaw viability of ASCs, suggesting that they are not susceptible to supra-zero cooling injury.Copyright © 2011 by ASME

A simple non-invasive method of cell retrieval using Methylcellulose (MC) coated Tissue Culture Poly-Styrone (TCPS) dishes was developed to allow the creation of single and multilayered adult stem cell sheet constructs while preserving the cell-cell and the cell–extracellular matrices. The optimal combination of MC-water-salt was found to be 12 to 14% of MC (mol. wt. of 15,000) in water with 0.5x PBS (∼150 mOsm). This solution exhibited a gel formation temperature of ∼32°C. The addition (evenly spread) of 200μl of 2mg/ml bovine collagen type -I (pH adjusted to 7.5) over the MC coated surface at 37°C, significantly improved the adult stem cell (ASC) adhesion and proliferation on the hydrogel system.Copyright © 2010 by ASME

The objective of this work was to assess the effect of 10% (w/v) polyvinylpyrrolidone (PVP) on the pattern of intracellular ice formation (IIF) in human adipose tissue derived adult stem cells (ASCs) in the absence of serum and other cryoprotective agents (CPAs).

Effective techniques for the cryopreservation of human Adipose Stem Cells (ASCs) could increase the usefulness of these cells in tissue engineering and regenerative medicine. The traditional method of using fetal calf serum (FCS) and a chemical cryoprotectant like dimethylsulfoxide (DMSO) during freezing storage restricts the direct use of ASCs in regenerative medicine and reconstruction surgery. The objective of this study was to investigate the apoptotic, necrotic and viability response of ASCs frozen/thawed in the presence of a high molecular weight polymer, Polyvinylpyrrolidone (PVP) and in the absence of FCS. Post-freeze/thaw studies were also conducted to evaluate the effect of PVP on the in vitro osteogenic and adipogenic differentiation of ASCs. The results were compared with those obtained using the most commonly used cryopreservation media of 10%DMSO + 10% Dulbecco’s Modified Eagle Media (DMEM) + 80%FCS.Copyright © 2009 by ASME

In the present study, we report the effects of cooling ejaculated and epididymal bovine sperm from the same animals with and without a cryoprotective agent, glycerol. Water transport data during freezing of ejaculated and epididymal bovine sperm cell suspensions were obtained at a cooling rate of 20 °C/min under two different conditions: i) in the absence of cryoprotective agents, CPAs; and ii) in the presence of 0.7 M glycerol. Using previously published values, the bovine sperm cell was modeled as a cylinder of length 39.8 μm and a radius of 0.4 μm with an osmotically inactive cell volume, Vb, of 0.61Vo, where Vo is the isotonic cell volume. The subzero water transport response is analyzed to determine the variables governing the rate of water loss during cooling of bovine spermatozoa, i.e. the membrane permeability parameters (reference membrane permeability, Lpg and activation energy, ELp). The predicted best-fit permeability parameters ranged from, Lpg = 0.021 to 0.038 μm/min-atm and ELp = 27.8 to 41.1 kcal/mol. The subzero water transport response and consequently the subzero water transport parameters are not significantly different between the ejaculated and epididymal bovine spermatozoa under corresponding cooling conditions. If this observation is found to be more generally valid for other mammalian species as well, then the sperm extracted from the testicles of an animal during post-mortem can also be optimally cryopreseved using procedures similar to those derived for ejaculated sperm.Copyright © 2008 by ASME

Flipchip assembly is the direct electrical connection of the device die on the substrates or circuit boards using conductive stud bumps. Stud bumps help in the reduction of the number of bond wires and weight, and improve performance. Ueno et al. [1] fabricated copper column bumps with a diameter of 75 μm, a height of 50 μm and a pitch of 200 μm. Ni/Au bumps were also fabricated using electroless plating method with a pitch of 50 μm [2]. Tomita et al. [3] successfully fabricated tip capped copper column bumps with a height of 5 μm that were spaced 100 μm apart. Lead free solder bumps have been fabricated using pure-tin (Sn), tin-bismuth (80wt%Sn:20wt%Bi), tin-copper (99.3wt%Sn:0.7wt%Cu), tin-silver (96.5wt%Sn:3.5wt%Ag), and tin-silver-copper (93.8wt%Sn:3.5wt%Ag:0.7wt%Cu) alloys with a diameter of 200 μm and a pitch of 400 μm [4]. Low cost gold bumps have also been fabricated on polymer substrates with dimensions of 40 μm in diameter, 41 μm in height and a pitch of 100μm [5]. More recently Chu et al. [6] have demonstrated the use of cylindrical indium solder bumps with 80 μm diameter for optical interconnect and microwave applications.

The objective of this study was to characterize the IIF behavior of Jurkat cells in isotonic conditions in the absence of any cryoprotective agents. The Jurkat cells were collected from culture and then washed and re-suspended in Dulbecco’s Phosphate Buffered Saline (PBS). The freezing experiments were carried out at defined freezing protocols and at various freezing rates of 5, 20, 30 and 50 °C/min. The results suggest there was no substantial evidence of intracellular ice formation at lower cooling rates of 5, 20 and 30° C/min. The first conspicuous indication of intracellular ice formation (IIF) was observed at a freezing rate of 50 °C/min. At this cooling rate, unlike the usual sudden blackening of cells, the cells suddenly grew and exploded suggesting the formation of intracellular ice, which was reminiscent of a prior observed phenomenon for IIF.Copyright © 2008 by ASME

In the present study, we report the effects of cooling ejaculated and epididymal rhesus monkey (Macaca mulatta) sperm in the presence of extracellular. Water transport data during freezing of ejaculated and epididymal sperm cell suspensions were obtained at a cooling rate of 20 °C/min in the absence of any cryoprotective agents. Additional water transport data was obtained from ejaculated sperm at a cooling of 5 °C/min without CPAs and at 20 °C/min in the presence of 0.7M of glycerol, as well. Using previously published values, the bovine sperm cell was modeled as a cylinder of length 73.83 μm and a radius of 0.32 μm with an osmotically inactive cell volume, Vb, of 0.772Vo, where Vo is the isotonic cell volume. The subzero water transport response is analyzed to determine the variables governing the rate of water loss during cooling of bovine spermatozoa, i.e. the membrane permeability parameters (reference membrane permeability, Lpg and activation energy, ELp). The predicted best-fit permeability parameters ranged from, Lpg = 0.0023 to 0.0029 μm/min-atm and ELp = 10.6 to 45.5 kcal/mol. The subzero water transport response and consequently the subzero water transport parameters are not significantly different between the ejaculated and epididymal macaque spermatozoa under corresponding cooling conditions.Copyright © 2008 by ASME

In a typical cryopreservation protocol, the system to be preserved is first equilibrated with chemicals known as cryoprotective agents (CPAs). CPAs have been shown to alleviate cell damage from either the solute effects or the formation of intracellular ice during the subsequent freezing process. Thus, an extensive body of literature reporting the effects of CPAs on cellular systems has been accumulated over the last 50 years; detailing largely experimental interactions between cell systems and chemicals. Recent advances in computational methodology now offer an additional dimension in our ability to understand the molecular interactions between cell membranes, idealized as lipid bilayers and CPAs at atomistic scales. Computer simulations provide unique capabilities for analyzing biomembrane properties from atomistic perspective with a degree of detail that is hard to reach by other techniques. The excellent agreement with the experiment obtained in various molecular dynamics (MD) studies [1] on simple model membranes has raised the confidence in applying the molecular dynamics simulations to even more complex systems. Dimethylsulfoxide (DMSO) is one of the most widely used solvents in cell biology and cryopreservation. During a typical cryopreservation protocol the DMSO composition of aqueous buffers inside and outside of the cell is known to differ considerably. To model and understand the structural changes in cell membranes in such a situation we performed MD simulations of an idealized lipid bilayer membrane which separates two aqueous reservoirs with and without DMSO. Zwitterionic dimyritoylphosphatidylcholine (DMPC) lipid bilayers was chosen as the model membrane.Copyright © 2008 by ASME