On the mechanical stability of polymeric microcontainers functionalized with nanoparticles
ABSTRACT We present key factors that influence the mechanical stability of polyelectrolyte/nanoparticle composite microcontainers and their encapsulation behavior by thermal shrinkage. Poly(diallyldimethylammonium chloride) (PDADMAC), poly(styrenesulfonate) (PSS) microshells and citrate-stabilized gold nanoparticles are used. The presence of nanoparticles in the microshell renders the encapsulation process by heat-shrinking more difficult. The encapsulation efficiency is found to decrease as the concentration of material to be encapsulated increases. Increasing nanoparticle content in the microshell or the concentration of dextran increases the likelihood of getting fused and damaged capsules during encapsulation. On the other hand, mechanical studies show that doping microshells with gold nanoparticles significantly increases their stiffness and resistance to deformation. Internalization of capsules by cells supports that the incorporation of metal nanoparticles makes the shells more resistant to deformation. This work provides information of significant interest for the potential biomedical applications of polymeric microshells such as intracellular storage and delivery.
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- "Mechanical force is applicable only at specific conditions permitting exerting the force. On the other hand, exerting mechanical forces can be used for measuring the stiffness  of capsules and the threshold forces  necessary for release. This approach is ideally suited for bench tests of capsules, but it is difficult to exert pressure on capsules in-vivo. "
ABSTRACT: Paving the way towards the application of polyelectrolyte multilayer capsules in theranostics, we describe diagnostic multi-functionality and drug delivery using multicompartment polymeric capsules which represent the next generation of drug delivery carriers. Their versatility is particularly important for potential applications in the area of theranostics wherein the carriers are endowed with the functionality for both diagnostics and therapy. Responsiveness towards external stimuli is attractive for providing controlled and on-demand release of encapsulated materials. An overview of external stimuli is presented with an emphasis on light as a physical stimulus which has been widely used for activation of microcapsules and release of their contents. In this article we also describe existing and new approaches to build multicompartment microcapsules as well as means available to achieve controlled and triggered release from their subcompartments, with a focus on applications in theranostics. Outlook for future directions in the area are highlighted.Theranostics 02/2013; 3(3):141-51. DOI:10.7150/thno.5846 · 8.02 Impact Factor
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ABSTRACT: New materials and process for future flip chip packaging have been studied. Three types of new concept materials with suitable process are discussed in this paper. First is the preset underfill (PUF) process. A non-conductive underfill film is used in this process by a flip chip-bonding machine with lamination capability. Throughput and reliability are mainly studied for this process. Basic reliability requirements such as Thermal Shock Test -40 C to +125 C/1000 cycles, Pressure Cooker Test 121 C×2 atm/168 hrs, and Moisture Sensitivity Level/JEDEC Level 3, have been achieved with high throughput. Second is the transfer underfill (TUF) material. A modified transfer molding machine instead of a liquid underfill dispensing machine does underfill in this process. The required characteristics for the transfer underfill material are no volatiles in the material pellet and good flow ability with gap below 100 μm. New TUF material has successfully clears the requirements with newly developed clean tablet (CT) technology, and filler particle distribution control. Third is an underfill paste (UFP) material. This new material has high thermal stability at operating temperatures up to 80 C, and rapid curing characteristics such as 150 C×20 min or 175 C×5 min, due to the special reaction control of the epoxy and phenol curing system. This material can be used in a current dispensing process with a minor adjustment in the heating parameter. Coating or printing processes are also available options for this UFP material. In this paper, the future of flip chip packages is discussed with these three materials and processesElectronic Components & Technology Conference, 2000. 2000 Proceedings. 50th; 02/2000