Microcapsule synthesis for 3D printing of self-healing materials

3D printing allows for the manufacture of finished structures from starting components with essentially no specialist training required. The process is autonomous; the starting components, such as inks, are poured into the machine and the finished product is produced with no intervention from the user. Currently, most commercial printers only produce structures which have limited functionality and are often used to produce ‘prototypes’ rather than a finished product. There have been recent advancements in the utilisation of 3D printing to produce structures which have longer lifespans, wider material choice and improved functionality, in order to extend the utility of printed structures beyond prototyping and expand potential applications. Within the research reported in this thesis, the focus is primarily on the production of 3D printing resins with embedded capsules, which can be utilised in 3D printers for the production of microcapsule containing composites. Specifically, theses capsules contain solvents and polymers which can be used for self-healing with the intention of extending the lifetime and toughness of any structures built by 3D printers using these materials.In this work, the 3D printing of self-healing materials is shown through the use of 3D printing resins modified with solvent and polymer containing urea-formaldehyde microcapsules. Urea- formaldehyde capsules are utilised widely in the literature for extrinsically self-healing microcapsule-based systems. The inclusion of the capsules showed no harmful effect on the quality of printing and mechanical testing showed the capability of fracture toughness recovery after healing via a classic solvent welding mechanism to be 48-59% depending on which solvent and concentration was used. The addition of poly(methyl methacrylate) chains into the core of the capsules and increasing the healing time to 72 hours enhanced the self-healing ability of the solvent anisole. Under these conditions, mechanical testing showed a capability for fracture toughness recovery of 87%.A more novel production route for microcapsules was also explored. The ability to generate an optically transparent self-healing system would be beneficial for utilisation in applications which require optically transparent materials. Microfluidic devices were utilised to produce microcapsules with a transparent resin shell and liquid oligomer core.Therefore, a key investigation for this work regarded the optimisation of capsule generation via droplet microfluidic devices. Droplet microfluidic devices generated the capsules in one at a time with sequential UV polymerisation in a continuous flow fashion, this proved an elegant solution to some of the problems seen when investigating production using a batch mixing process. Despite concerns with regards to high viscosities (230-11,000 mPa s) and the complex rheology associated with polymer blends, it was shown that droplet generation can be controlled via microfluidics. This fixed some issues seen when trying to optimise this process using batch synthesis routes, producing superior capsules than a due to the high degree of control afforded by microfluidic devices.These capsules were successfully utilised in a 3D printer and the reduced light scattering from these microcapsules when compared to the urea-formaldehyde capsules was significant. Here, we show that this mechanism had the ability to recover fracture toughness of up to 83%

Stereolithographic 3D printing of extrinsically self-healing composites

We demonstrate for the first time the direct stereolithographic 3D printing of an extrinsically self-healing composite, comprised of commercial photocurable resin modified with anisole and PMMA-filled microcapsules. The composites demonstrate solvent-welding based autonomous self-healing to afford 87% recovery of the initial critical toughness. This work illustrates the potential of stereolithographic printing to fabricate self-healing composites with user-defined structures, avoiding the need for extensive rheological optimization of printing inks, like in direct-write 3D printing. Importantly, this work also demonstrates the inclusion of microcapsules into 3D printing resins to incorporate additional functionality into printed composites, which could be adapted for applications beyond self-healing materials

Organizational interventions employing principles of complexity science have improved outcomes for patients with Type II diabetes

<p>Abstract</p> <p>Background</p> <p>Despite the development of several models of care delivery for patients with chronic illness, consistent improvements in outcomes have not been achieved. These inconsistent results may be less related to the content of the models themselves, but to their underlying conceptualization of clinical settings as linear, predictable systems. The science of complex adaptive systems (CAS), suggests that clinical settings are non-linear, and increasingly has been used as a framework for describing and understanding clinical systems. The purpose of this study is to broaden the conceptualization by examining the relationship between interventions that leverage CAS characteristics in intervention design and implementation, and effectiveness of reported outcomes for patients with Type II diabetes.</p> <p>Methods</p> <p>We conducted a systematic review of the literature on organizational interventions to improve care of Type II diabetes. For each study we recorded measured process and clinical outcomes of diabetic patients. Two independent reviewers gave each study a score that reflected whether organizational interventions reflected one or more characteristics of a complex adaptive system. The effectiveness of the intervention was assessed by standardizing the scoring of the results of each study as 0 (no effect), 0.5 (mixed effect), or 1.0 (effective).</p> <p>Results</p> <p>Out of 157 potentially eligible studies, 32 met our eligibility criteria. Most studies were felt to utilize at least one CAS characteristic in their intervention designs, and ninety-one percent were scored as either "mixed effect" or "effective." The number of CAS characteristics present in each intervention was associated with effectiveness (p = 0.002). Two individual CAS characteristics were associated with effectiveness: interconnections between participants and co-evolution.</p> <p>Conclusion</p> <p>The significant association between CAS characteristics and effectiveness of reported outcomes for patients with Type II diabetes suggests that complexity science may provide an effective framework for designing and implementing interventions that lead to improved patient outcomes.</p

Early Exit: Estimating and explaining early exit from drug treatment

Background: Early exit (drop-out) from drug treatment can mean that drug users do not derive the full benefits that treatment potentially offers. Additionally, it may mean that scarce treatment resources are used inefficiently. Understanding the factors that lead to early exit from treatment should enable services to operate more effectively and better reduce drug related harm. To date, few studies have focused on drop-out during the initial, engagement phase of treatment. This paper describes a mixed method study of early exit from English drug treatment services. Methods: Quantitative data (n = 2,624) was derived from three English drug action team areas; two metropolitan and one provincial. Hierarchical linear modelling (HLM) was used to investigate predictors of early-exit while controlling for differences between agencies. Qualitative interviews were conducted with 53 ex-clients and 16 members of staff from 10 agencies in these areas to explore their perspectives on early exit, its determinants and, how services could be improved. Results: Almost a quarter of the quantitative sample (24.5%) dropped out between assessment and 30 days in treatment. Predictors of early exit were: being younger; being homeless; and not being a current injector. Age and injection status were both consistently associated with exit between assessment and treatment entry. Those who were not in substitution treatment were significantly more likely to leave treatment at this stage. There were substantial variations between agencies, which point to the importance of system factors. Qualitative analysis identified several potential ways to improve services. Perceived problems included: opening hours; the service setting; under-utilisation of motivational enhancement techniques; lack of clarity about expectations; lengthy, repetitive assessment procedures; constrained treatment choices; low initial dosing of opioid substitution treatment; and the routine requirement of supervised consumption of methadone. Conclusion: Early exit diminishes the contribution that treatment may make to the reduction of drug related harm. This paper identifies characteristics of people most likely to drop out of treatment prematurely in English drug treatment services and highlights a range of possibilities for improving services

Working with Wikis in Writing-Intensive Classes

Most teachers, having too little time and too much experience with the next-new-thing, tend to turn a deaf ear to the fanfare heralding new technologies such as wikis. They are unlikely to try wikis, blogs and other Web 2.0 innovations without concrete evidence of their pedagogic value. Much that has been published to date on wiki use in college classes either explains what wikis are or speculates on what they might accomplish. Few studies, notably those of Farabaugh (2007), Carr, Morrison, Cox and Deacon (2007) and James (2007), analyze how wikis have and have not worked when actually used in college classes. To this end, we report on a study conducted over two quarters, with three classes and two teaching teams in a program that serves non-traditional students. We studied our use of wikis as a learning tool (helping students develop academic writing skills) and as a teaching tool (allowing us to distribute information, promote collaboration and build a sense of class community). We also evaluated one teaching team\u27s ability to develop their use of the wiki and disseminate what they learned to another teaching team

Working with Wikis in Writing-Intensive Classes

Most teachers, having too little time and too much experience with the next-new-thing, tend to turn a deaf ear to the fanfare heralding new technologies such as wikis. They are unlikely to try wikis, blogs and other Web 2.0 innovations without concrete evidence of their pedagogic value. Much that has been published to date on wiki use in college classes either explains what wikis are or speculates on what they might accomplish. Few studies, notably those of Farabaugh (2007), Carr, Morrison, Cox and Deacon (2007) and James (2007), analyze how wikis have and have not worked when actually used in college classes. To this end, we report on a study conducted over two quarters, with three classes and two teaching teams in a program that serves non-traditional students. We studied our use of wikis as a learning tool (helping students develop academic writing skills) and as a teaching tool (allowing us to distribute information, promote collaboration and build a sense of class community). We also evaluated one teaching team\u27s ability to develop their use of the wiki and disseminate what they learned to another teaching team

Rates of early exit by agency (includes only agencies with at least 20 people entering treatment)

<p><b>Copyright information:</b></p><p>Taken from "Early exit: Estimating and explaining early exit from drug treatment"</p><p>http://www.harmreductionjournal.com/content/5/1/13</p><p>Harm Reduction Journal 2008;5():13-13.</p><p>Published online 25 Apr 2008</p><p>PMCID:PMC2391146.</p><p></p

Ah, the apple trees, blossoms in the breeze, that we walked [first line of chorus]

Performers: Bing Crosby, Toni Arden, Bob Sands, Felicia Sanders, Polly Bergen, Leo MarjanePiano, Voice and Chord