35 results found
Shah UV, Inguva K, Tan B, et al., 2022, CREATE labs – Student centric hybrid teaching laboratories, Education for Chemical Engineers, Vol: 37, Pages: 22-28, ISSN: 1749-7728
The CREATE labs, a hybrid laboratory experience suitable for remote learning was developed at Imperial College in response to the COVID-19 pandemic. To facilitate the transformation from traditional to remote labs, a systematic review of offered projects was carried out to identify where learning objectives could be met using remote-friendly options such as simulations. Essential physical experiments were performed through the use of various technologies including online collaboration software and first-person point of view cameras to enable a high level of student involvement. Student surveys and interviews confirmed a positive experience comparable to previous years with an improvement in feedback provision.
Bhute V, Sengupta S, Campbell J, et al., 2022, Effectiveness of a large-scale implementation of hybrid labs for experiential learning at Imperial College London, Education for Chemical Engineers, Vol: 39, Pages: 58-66, ISSN: 1749-7728
Experiential learning is an integral component of engineering education. The Chemeng Remote Experience Augmented through TEchnology (CREATE) labs concept was implemented in the academic year 2020–21 in response to COVID19 for first-, second-, and third-year chemical engineering undergraduate students studying at Imperial College London. Using a range of technologies including pan-tilt-zoom cameras and Microsoft HoloLens 2 to provide real-time views of the lab environment from anywhere in the world. Students could control the experiments remotely while graduate teaching assistants (GTAs) operated the equipment based on the students’ instructions. This study is aimed at assessing the effectiveness of this implementation with a focus on student communication and confidence. Students and GTAs were surveyed at the end of labs, and a year-dependent response was observed. The majority of students (>70%) reported experiencing effective communication with team members and GTAs and there was a strong positive correlation between communication and confidence in applying engineering concepts in the labs (χ2 = 79.96; p = 1.69 ×10−10). 5–10% of students from all year groups reported that they disliked the lack of in-person activities. The majority (>90%) of GTAs assisting with experiments stated that they associated their role in the CREATE labs with that of a facilitator. The overall delivery of CREATE labs during academic year 2020–21 was positively received by both students and GTAs with recommendations for in-person activities for first- and second-year students. With minor modifications, CREATE labs has the potential to prepare students for effective remote communication and gain experience in using smart technologies which are key components of Industry 4.0.
Chadha D, Campbell J, Maraj M, et al., 2022, Engaging students to shape their own learning: driving curriculum re-design using a Theory of Change approach, Education for Chemical Engineers, Vol: 38, Pages: 14-21, ISSN: 1749-7728
Curriculum review is challenging, although if carried out strategically can be less so. The adoption of a theory of change approach for reviewing a chemical engineering curriculum at a research-intensive university in the UK is discussed. The curriculum review was undertaken as part of an institutional drive to modularise the curricula and align the number of contact and independent study hours for all undergraduate students in the institution. At the heart of our curriculum review is the student experience, which is often ignored in favour of the views of institutional management. The curriculum has been redesigned using a theory of change approach, which has enabled us to establish short and long-term plans based on our efforts to create a less burdensome, student-centred curriculum that incorporates our institutional learning and teaching strategy. As part of the process, assumptions needed to be surfaced, meaningful evidence collated, and a central end-goal identified These plans are evidence-based and include: the provision of a departmental wellbeing advisor, the application and development of interactive pedagogies, appropriate mechanisms that support slow learning through formative assessment and less of an assessment burden, and nurturing links with industry-based partners ensuring a greater emphasis on students’ professional development and their exposure to chemical engineering industries.
Chadha D, Kogelbauer A, Campbell J, et al., 2021, Are the kids alright? Exploring students’ experiences of support mechanisms to enhance wellbeing on an engineering programme in the UK, European Journal of Engineering Education, Vol: 46, Pages: 662-677, ISSN: 0304-3797
In this paper, we aim to explore students’ experiences of support mechanisms that support their wellbeing on an engineering degree programme at a research-intensive higher education institution and understand how theory relates to practice. This study was conducted using a mixed-methods approach involving student survey responses (N = 173), interviews with 16 students and focus groups. Kahu and Nelson’s conceptual framework was used as a lens through which to explore student support mechanisms. Preliminary data analysis indicates that the intense workload adversely affects students as do some of the interactions they have with personal tutors and their peers. Our findings suggest that workload needs to be reduced, personal tutors need to fill gaps in their skills set, especially associated with student support, and institutional and departmental protocols be continually updated to support student wellbeing. Additionally, student wellbeing officers and professional, dedicated wellbeing advisors could be part of a long-term solution.
Inguva K, Shah P, Shah U, et al., 2021, How to design experiential learning resources for independent learning, Journal of Chemical Education, Vol: 98, Pages: 1182-1192, ISSN: 0021-9584
Key components of any experiential learning module are the resources students use to learn. These typically include laboratory equipment, handouts, and instructional material in the form of videos or standard operating procedures (SOPs). Their design and implementation require careful thought to ensure that students learn in an effective and meaningful way. From our own experience in the undergraduate teaching laboratory and from a variety of literature sources, we have identified five design principles that educators should consider and integrate into their resource development workflows: safety, authenticity, flexibility, accessibility, and robustness (SAFAR). We present several examples of how each principle can be implemented using Kolb’s experiential learning cycle as a lens to understand the impact of each design principle on the learning process.
Bhute VJ, Inguva P, Shah U, et al., 2021, Transforming traditional teaching laboratories for effective remote delivery—A review, Education for Chemical Engineers, Vol: 35, Pages: 96-104, ISSN: 1749-7728
Teaching laboratories form an essential component of any engineering education. They enable students to participate in various stages of experiential learning including conceptualization and experimentation followed by reflection, analysis and interpretation of data. However, operating teaching laboratories with social distancing measures poses significant logistical and safety challenges, and alternative modes of delivery may be a realistic way forward in adapting engineering curricula to the post COVID-19 world. Best practices from spaces such as distance learning and virtual / remote laboratories can be leveraged to facilitate educators’ responses. This review is aimed at identifying evidence-based approaches for transforming hands-on labs into virtual or remote operation to achieve desired learning outcomes without compromising on soft skills and student self-efficacy. A critical review of the recent literature on delivering STEMM education laboratories in either a virtual or remote setting or a combination of both is presented here. Commonly emerging approaches are identified and strategies to implement remote or mixed-mode (a combination of remote and traditional lab components) delivery are highlighted. The value of these approaches to the educator is assessed based on claimed learning outcomes, availability of resources, technology, scheduling, and cost factors.
Campbell J, Macey A, Chen W, et al., 2020, Creating a confident and curious cohort: The effect of video-led instructions on teaching first-year chemical engineering laboratories, Journal of Chemical Education, Vol: 97, Pages: 4001-4007, ISSN: 0021-9584
On-demand video has become a seamless part of the fabric of information consumption. Initially inspired by the popularity of video guides for practical skills such as cooking and DIY, instructional videos were developed for equipment used in the first-year chemical engineering undergraduate teaching laboratory at Imperial College London. During 2016/2017, the effect of the videos on the students’ learning was measured using video viewership metrics, a survey, focus groups with students and Graduate Teaching Assistants (GTAs) and rounded off through interviews with the module teaching team. Student reactions were overall positive, with >90% of students stating they found the videos useful. The outcome of our study indicated that because of access to the videos before, during, and after lab sessions, students were more confident in their own ability, spent more time engaging with theory, applied practical lab skills in a more targeted way, and produced better outputs. Rather than being just a video version of the experiment handout, the video influenced the behavior of both learners and teachers, freeing up time to engage in deeper exploration of topics. The results of the study suggest that the use of video-led instruction in undergraduate laboratory teaching improves student experience, saves GTA time, and decidedly shifts the teaching focus from demonstration to exploration.
Bhute V, Campbell J, Kogelbauer A, et al., 2020, Moving to timed remote assessments: the impact of COVID-19 on year end exams in Chemical Engineering at Imperial College London, Journal of Chemical Education, Vol: 97, Pages: 2760-2767, ISSN: 0021-9584
Summative year end assessments area major component of student assessment at the Department of Chemical Engineering, Imperial College London.More than 600 studentsparticipate in over40 different exams during the summer term. At the end of the spring term, the college moved to fully remote operation due to COVID-19, leaving the academic community with the challenge of delivering examinationsremotely. At the time pandemic hit the UK, teaching for allmodules in the department had been completed, the exam timetable had already been published and all exam paperspassed the mandatory external quality review. To implement time-limited remote examsas stipulated by the university, the department decided to proceed with anexisting VLE platformfor submission of answer-sheets.This study highlights stakeholder reflections from the academic and student communityduring the implementation of this approachculminating in a mock examination to gauge readiness of the infrastructure as well as the student population.Our survey found that the majority of students (>80%) managed to follow the written instructionsand readily engaged with scanning technologies and the uploading process.In the main, students did not have to adapt their learning or writing style. All stakeholdersprovided constructive suggestions at the end of the mock exam resulting in a relatively smooth transition to this new mode of examination. This study highlights challenges and reflections on making the summer year end examsremote in a very short timeframein a large and diverse Chemical Engineering department at very short notice.
Xie M, Inguva K, Chen W, et al., 2020, Accelerating students’ learning of chromatography with an experiential module on process development and scaleup, Journal of Chemical Education, Vol: 97, Pages: 1001-1007, ISSN: 0021-9584
The objective of the presented module is to train students with no background in process development and scaleup of chromatographic processes to a high level of competency within 40 contact hours. The key pedagogical approach is “progression” where students’ capabilities are gradually built up with appropriate scaffolding provided at each stage of their learning. The module is broken up into three steps, with each step covering a different aspect of chromatography. Knowledge gained in one step is the foundation for work in the next. In the first step, students investigate several chromatographic column packing materials and perform a solvent selection process. Design of experiment (DOE) to systematically vary process parameters for method development is introduced in the second step. In the last step, students use a preparative-LC system to perform a larger-scale separation. Students explore different scale-up scenarios, including volume fraction collection and column overloading. Pedagogic outcomes of the module were determined through surveys, interviews, and personal interaction during the study. Results clearly indicate that students engaged well with the module while meeting overall learning objectives. The module is equally suitable for third- or fourth-year university students or industry practitioners unfamiliar with chromatography as part of continuing professional development.
Shah UV, Chen W, Inguva K, et al., 2020, The discovery laboratory part II: A framework for incubating independent learning, Education for Chemical Engineers, Vol: 31, Pages: 29-37, ISSN: 1749-7728
We have conceptualized the Discovery Laboratory at Imperial College London into an educational framework that enables independent learning among students. The study demonstrates an effective implementation of the framework with associated benefits for the learner in the areas of cognitive skills (creativity and critical thinking), metacognitive skills (ability to reflect on the entire learning process) and affective skills (adaptive motivation). Key supportive elements were transferring ownership of the learning process to students and incorporating assessment criteria that reward creativity. The framework can be easily adapted to other experiential learning contexts.
Kalogeropoulos N, Walker P, Hale C, et al., 2020, Facilitating Independent Learning: Student Perspectives on the Value of Student-Led Maker Spaces in Engineering Education, INTERNATIONAL JOURNAL OF ENGINEERING EDUCATION, Vol: 36, Pages: 1220-1233, ISSN: 0949-149X
Chen W, Shah U, Brechtelsbauer C, 2019, A framework for hands-on learning in chemical engineering education—Training students with the end goal in mind, Education for Chemical Engineers, Vol: 28, Pages: 25-29, ISSN: 1749-7728
Chemical engineering education aims to equip students with both theoretical knowledge and hands-on capability to solve practical problems. At Imperial College London, this is practiced via three laboratory-based courses, which span over the first three years of the undergraduate curriculum. The Foundation, Knowledge and Discovery Laboratories were designed based on Kolb’s experiential learning theory as well as Vygotsky’s zone of proximal development. Although these courses intend to challenge students, appropriate scaffolding is in place to ensure a satisfactory learning experience across the spectrum of abilities. Assessment and survey results show that all students were capable of meeting the learning goals (>96% achieving satisfactory to excellent results in academic years 2014–2016), while a large majority is satisfied with the courses (>80% in academic years 2014–2016). The design and implementation of these courses are discussed to promote the exchange of good practices within the higher education community.
Chadha D, Maraj M, Kogelbauer A, et al., 2019, Hearing you loud and clear: The student voice as a driver for curriculum change in a chemical engineering degree course (WIP), ASEE Annual Conference and Exposition 2019, Publisher: ASEE
A curriculum review can be an intricate and arduous process, made more complex due to a myriad of interwoven threads that inform the curriculum. This is often the case in chemical engineering due in part to the accommodation of employer expectations, requirements from accreditation bodies and the multidisciplinary, integrative nature of an engineering degree which depends on students acquiring a wide range of attributes, and which focuses on application and relevancy , . In this paper, we present our efforts to review the chemical engineering curricula at a research-intensive higher education institution (HEI)in the UK. This review is being orchestrated by institutional managers to ensure that programmes of study throughout the HEI better reflect student needs and expectations and adhere to a recently revised institutional teaching and learning strategy. This review is also driven by a recognition that the student body has changed with traditional modes of teaching seemingly outdated and ineffective. For example, it has previously been suggested that one of the greatest obstacles to overcome with respect to creating the right type of education for chemical engineers, does not arise from external drivers, but in recognising and responding to internal factors –amounting to fundamental pedagogical shifts in learner behaviour and expectation.
Inguva P, Teck A, Anabaraonye B, et al., 2018, Advancing experiential learning through participatory design, Education for Chemical Engineers, Vol: 25, Pages: 16-21, ISSN: 1749-7728
Participatory design (PD) as a module development tool offers significant potential to enhance experiential learning courses such as laboratory modules. Involvement of students and other stakeholders results in pre-delivery feedback on module design, implementation strategy, and teaching material. In this study, PD was employed for design and development of a systems control and reaction engineering laboratory project. The nature of stakeholder interaction at various levels was analysed and specific examples for how such an approach improved the development process is presented. Current students provided feedback on how the module was perceived by their peers and participated in developing solutions to make the learning process more inclusive. Senior students and graduate teaching assistants (GTAs) were able to contribute at a higher technical design level. Students were intellectually stimulated by the module design, enhancing the overall teaching and learning process.
Macey A, Campbell J, Chen W, et al., 2018, Transforming the role of demonstrators through video led instructions, International Symposium of Engineering Education 2018, Publisher: ISEE
Video on-demand has become a seamless part in the fabric of society’s information consumption. Although videos are common place as a demonstration medium for simple experiments, they have not been used widely as a training tool in teaching laboratories. In this study, we focus on employing video on location to provide practical instructions in authentic settings.Over 10 instructional videos of first year laboratory experiments in chemical engineering were filmed, each providing detailed operational information. The whole cohort of over 140 students performed two experiments without videos under the traditional demonstration regime, and the remaining five experiments with video led instructions. More than 90% of students found the instructional videos useful, and 75% of students confirmed that this approach improved their teaching and learning experience. Over 95% of the students who participated in the survey recommended using videos as an instructional medium. Because of ready access to the videos, students were more confident in their practical abilities and spent more time engaging with theory to produce better informed outputs. Instead of focusing on operational issues, teaching staff had time to engage with students in discussions to explore topics in more depth.Rather than just being perceived as live-action versions of experiment hand-outs, the instructional videos actually changed outcomes for both learners and educators. Results indicate that the student experience was significantly enhanced and the teaching focus shifted from demonstration to exploration by transforming the role of demonstrators to facilitators and mentors.
An experiment to aid the transition from secondary school chemistry to introductory chemical engineering in higher education is described. The phenomenon of chemiluminescence observed during the oxidation of luminol has been successfully employed to study the kinetics of the reaction. Using inexpensive light sensors the effects of temperature on rate of chemical reactions can easily be quantified through their associated kinetic parameters.The experiment gives reproducible results and allows the measurement of the rate constants of the reaction and its order with respect to luminol at different temperatures in one three hour laboratory session. From these, the activation energy of the reaction can be determined. Experimental skill and supervisory requirements are minimal making the setup ideal for first year undergraduate or final stage secondary school students.
Shah UV, Jahn NH, Huang S, et al., 2017, Crystallisation via novel 3D nanotemplates as a tool for protein purification and bio-separation, Journal of Crystal Growth, Vol: 469, Pages: 42-47, ISSN: 0022-0248
This study reports an experimental validation of the surface preferential nucleation of proteins on the basis of a relationship between nucleant pore diameter and protein hydrodynamic diameter. The validated correlation was employed for the selection of nucleant pore diameter to crystallise a target protein from binary, equivolume protein mixture. We report proof-of-concept preliminary experimental evidence for the rational approach for crystallisation of a target protein from a binary protein mixture on the surface of 3D nanotemplates with controlled surface porosity and narrow pore-size distribution selected on the basis of a relationship between the nucleant pore diameter and protein hydrodynamic diameter. The outcome of this study opens up an exciting opportunity for exploring protein crystallisation as a potential route for protein purification and bio-separation in both technical and pharmaceutical applications.
Shah UV, Karde V, Ghoroi C, et al., 2017, Influence of particle properties on powder bulk behaviour and processability, International Journal of Pharmaceutics, Vol: 518, Pages: 138-154, ISSN: 1873-3476
Understanding interparticle interactions in powder systems is crucial to pharmaceutical powder processing. Nevertheless, there remains a great challenge in identifying the key factors affecting interparticle interactions. Factors affecting interparticle interactions can be classified in three different broad categories: powder properties, environmental conditions, and powder processing methods and parameters. Although, each of these three categories listed is known to affect interparticle interactions, the challenge remains in developing a mechanistic understanding on how combination of these three categories affect interparticle interactions. This review focuses on the recent advances on understanding the effect of powder properties, particularly particle properties, its effect on interparticle interactions and ultimately on powder bulk behaviour. Furthermore, this review also highlights how particle properties are affected by the particle processing route and parameters. Recent advances in developing a particle processing route to prepare particles with desired properties allowing desired interparticle interaction to deliver favoured powder bulk behaviour are also discussed. Perspectives for the development of potential particle processing approaches to control interparticle interaction are presented.
Smith RR, Shah UV, Parambil JV, et al., 2016, The effect of polymorphism on surface energetics of D-mannitol polymorphs, AAPS Journal, Vol: 19, Pages: 103-109, ISSN: 1550-7416
The aim of this work was to assess the effect of different crystalline polymorphism on surface energetics of D-mannitol using finite dilution inverse gas chromatography (FD-IGC). Pure α, β and δ polymorphs were prepared via solution crystallisation and characterised by powder X-ray diffraction (P-XRD). The dispersive surface energies were found to range from 43 to 34 mJ/m(2), 50 to 41 mJ/m(2), and 48 to 38 mJ/m(2) , for α, β, and δ, respectively, for surface coverage ranging from 0.006 to 0.095. A deconvolution modelling approach was employed to establish their energy sites. The primary sites corresponded to maxima in the dispersive surface energy of 37.1 and 33.5; 43.3 and 39.5; and 38.6, 38.4 and 33.0; for α, β, and δ, respectively. This methodology was also extended to an α-β polymorph mixture to estimate the amount of the constituent α and β components present in the sample. The dispersive surface energies of the α-β mixture were found to be in the range of 48 to 37 mJ/m(2) with 40.0, 42.4, 38.4 and 33.1 mJ/m(2) sites. The deconvolution modelling method extracted the energy contribution of each of the polymorphs from data for the polymorphic mixture. The mixture was found to have a β-polymorph surface content of ∼19%. This work shows the influence of polymorphism on surface energetics and demonstrates that FD-IGC coupled with a simple modelling approach to be a powerful tool for assessing the specific nature of this energetic distribution including the quantification of polymorphic content on the surface.
Shah U, Chen W, Brechtelsbauer C, 2016, The discovery laboratory – A student-centred experiential learning practical: Part I – Overview, Education for Chemical Engineers, Vol: 17, Pages: 44-53, ISSN: 1749-7728
Chemical Engineering’s Discovery Laboratory at Imperial College London is a practical teaching programme designed specifically to support student-centred learning at an advanced level, bridging the gap between instructions driven lab experiments and fully open ended research. In the first part of this article we present an overview of this programme with particular attention given to the design of the pedagogical framework and the execution of teaching. The teaching goal is delivered by in-depth experiential learning, where students are assigned a specific subject area to conduct their own research within a set timeframe and boundary conditions that guarantee a successful learning outcome. Academic supervisors and teaching assistants play an important role in this process, where they provide students with continuing guidance throughout. The use of research or industrial grade equipment ensures the students’ preparation for their final year research project as well as their post-graduation careers. In addition to summative assessments, students also receive formative feedback periodically from academic supervisors and teaching assistants. The Discovery Laboratory has received positive feedback from both teachers and students since its inauguration in 2011 and here we share some useful insights for the execution of such a practical teaching programme.
Brechtelsbauer C, Haslam A, Shah U, et al., 2016, Measuring vapour pressure with an isoteniscope - a hands-on introduction to thermodynamic concepts, Journal of Chemical Education, Vol: 93, Pages: 920-926, ISSN: 1938-1328
Characterization of the vapor pressure of a volatile liquid or azeotropic mixture, and its fluid phase diagram, can be achieved with an isoteniscope and an industrial grade digital pressure sensor using the experimental method reported in this study. We describe vapor-pressure measurements of acetone and n-hexane and their azeotrope, and how the data can be used to calculate thermodynamic properties of the test liquids, such as the molar heat of vaporization. This hands-on experience allows students to appreciate important thermodynamic concepts such as phase equilibrium, preparing them for more advanced studies of the subject.
Wang Z, Shah UV, Olusanmi D, et al., 2015, Measuring the sticking of mefenamic acid powders on stainless steel surface, International Journal of Pharmaceutics, Vol: 496, Pages: 407-413, ISSN: 0378-5173
Al Nasser WN, Shah UV, Nikiforou K, et al., 2015, Effect of silica nanoparticles to prevent calcium carbonate scaling using an in situ turbidimetre, Chemical Engineering Research and Design, Vol: 110, Pages: 98-107, ISSN: 0263-8762
Scale minerals in the oil and gas industries are a major concern to reservoir and operations engineering. The main types of oilfield scales found are carbonate and sulfate scales. Calcium carbonate (CaCO3) is a major component of fouling in heat transfer surfaces across different sectors of industry, resulting in additional capital, maintenance and operating costs. Various techniques, including the use of chemical inhibitors, have been used to prevent the formation of scale. In the last decade, there have been considerable advances in the development of chemicals, effective in small concentrations for the control of scale deposits.The purpose of this study was to investigate the possibilities of utilizing nanoparticles as sacrificial surface for enhancement and control of the nucleation and crystallization of CaCO3, as a method for fouling mitigation. Here, the turbidity profile of the solution, using a light reflection technique, is used to monitor the process. The outcomes of this study will improve revenues by preventing the unscheduled shutdown of facilities and avoidance of using an excess of scale inhibitors. Silica nanoparticles of different size and surface functional groups were added to the solution. The results showed a reduction in the induction period, consequently indicating improved control over crystallization. Modified silica nanotemplates exhibited the highest reduction in induction time at room temperature. This resulted in preventing scale formation on the wall of the crystallizer. This conclusion is very significant, and further studies are proposed, which will attempt to understand the mechanisms of reactions between the nanoparticles and scaling ions.
Shah UV, Wang Z, Olusanmi D, et al., 2015, Effect of milling temperatures on surface area, surface energy and cohesion of pharmaceutical powders, International Journal of Pharmaceutics, Vol: 495, Pages: 234-240, ISSN: 0378-5173
Shah UV, Amberg C, Diao Y, et al., 2015, Heterogeneous nucleants for crystallogenesis and bioseparation, CURRENT OPINION IN CHEMICAL ENGINEERING, Vol: 8, Pages: 69-75, ISSN: 2211-3398
Shah UV, Parambil JV, Williams DRM, et al., 2015, Preparation and characterisation of 3D nanotemplates for protein crystallisation, Powder Technology, Vol: 282, Pages: 10-18, ISSN: 0032-5910
Heterogeneous template nucleants are gaining pace as a favoured tool for crystallisation of proteins that may be otherwise difficult to crystallise. A systematic understanding on protein-nucleant interactions has to be developed to enable the development of nucleants for a wide spectrum of biological macromolecules. Thorough characterisation of the nucleants is the key starting point to achieve this aim. This report focuses on the method to produce and characterise functionalised 3D nanotemplates with controlled porosity in the range of 3-22. nm and surface chemistry that can vary from highly hydrophilic to highly hydrophobic in nature. BET and TEM are used to study porosity and pore size distribution while contact angle, XPS and zeta potential are used to investigate surface chemistry of the nucleants. These functionalised 3D nanotemplates are hereby reported to produce protein crystals (concanavalin A and catalase) of different habits without changing any other crystallisation parameters other than the surface chemistry of the templates. This emphasises the potential of 3D nanotemplates with well-ordered porosity and chemistry for further development in protein crystallisation experiments.
Shah UV, Olusanmi D, Narang AS, et al., 2015, Decoupling the Contribution of Surface Energy and Surface Area on the Cohesion of Pharmaceutical Powders, Pharmaceutical Research, Vol: 32, Pages: 248-259, ISSN: 1573-904X
PurposeSurface area and surface energy of pharmaceutical powders are affected by milling and may influence formulation, performance and handling. This study aims to decouple the contribution of surface area and surface energy, and to quantify each of these factors, on cohesion.MethodsMefenamic acid was processed by cryogenic milling. Surface energy heterogeneity was determined using a Surface Energy Analyser (SEA) and cohesion measured using a uniaxial compression test. To decouple the surface area and surface energy contributions, milled mefenamic acid was “normalised” by silanisation with methyl groups, confirmed using X-ray Photoelectron Spectroscopy.ResultsBoth dispersive and acid–base surface energies were found to increase with increasing milling time. Cohesion was also found to increase with increasing milling time. Silanised mefenamic acid possessed a homogenous surface with a surface energy of 33.1 ± 1.4 mJ/m2 , for all milled samples. The cohesion for silanised mefenamic acid was greatly reduced, and the difference in the cohesion can be attributed solely to the increase in surface area. For mefenamic acid, the contribution from surface energy and surface area on cohesion was quantified to be 57% and 43%, respectively.ConclusionsHere, we report an approach for decoupling and quantifying the contribution from surface area and surface energy on powder cohesion.
Shah UV, Olusanmi D, Narang AS, et al., 2014, Decoupling the contribution of dispersive and acid-base components of surface energy on the cohesion of pharmaceutical powders, International Journal of Pharmaceutics, Vol: 475, Pages: 592-596, ISSN: 1873-3476
This study reports an experimental approach to determine the contribution from two different components of surface energy on cohesion. A method to tailor the surface chemistry of mefenamic acid via silanization is established and the role of surface energy on cohesion is investigated. Silanization was used as a method to functionalize mefenamic acid surfaces with four different functional end groups resulting in an ascending order of the dispersive component of surface energy. Furthermore, four haloalkane functional end groups were grafted on to the surface of mefenamic acid, resulting in varying levels of acid-base component of surface energy, while maintaining constant dispersive component of surface energy. A proportional increase in cohesion was observed with increases in both dispersive as well as acid-base components of surface energy. Contributions from dispersive and acid-base surface energy on cohesion were determined using an iterative approach. Due to the contribution from acid-base surface energy, cohesion was found to increase ∼11.7× compared to the contribution from dispersive surface energy. Here, we provide an approach to deconvolute the contribution from two different components of surface energy on cohesion, which has the potential of predicting powder flow behavior and ultimately controlling powder cohesion.
Cole K, Buffler A, Cilliers JJ, et al., 2014, A surface coating method to modify tracers for positron emission particle tracking (PEPT) measurements of froth flotation, Powder Technology, Vol: 263, Pages: 26-30, ISSN: 0032-5910
Positron emission particle tracking (PEPT) is a technique by which particle behaviour can be measured in a system of flow. The quality of the measurement is related to the spatial and temporal precision of the PET scanner and the characteristics of the tracer, which must replicate physical and chemical properties of the system bulk. Tracer particles can be made from ion exchange resins which have a high capacity for the commonly used positron emitting radionuclides 18F or 68Ga. However, these resins have a polymer composition and are naturally hydrophilic, which limits their application in systems involving mineral particles. This work presents a method to modify ion exchange resins with a coating to change the physical properties of the tracer. Two types of tracer were fabricated in this way, with hydrophobic and hydrophilic surfaces, to investigate the behaviour of valuable and gangue minerals in froth flotation with PEPT. The PEPT data were used to determine the spatial occupancies of each tracer, showing that the hydrophobic tracer has the highest occupancy in the froth region and the hydrophilic tracer is rarely entrained.
Shah UV, Olusanmi D, Narang AS, et al., 2014, Effect of crystal habits on the surface energy and cohesion of crystalline powders, International Journal of Pharmaceutics, Vol: 472, Pages: 140-147, ISSN: 1873-3476
The role of surface properties, influenced by particle processing, in particle–particle interactions (powder cohesion) is investigated in this study. Wetting behaviour of mefenamic acid was found to be anisotropic by sessile drop contact angle measurements on macroscopic (>1 cm) single crystals, with variations in contact angle of water from 56.3° to 92.0°. This is attributed to variations in surface chemical functionality at specific facets, and confirmed using X-ray photoelectron spectroscopy (XPS). Using a finite dilution inverse gas chromatography (FD-IGC) approach, the surface energy heterogeneity of powders was determined. The surface energy profile of different mefenamic acid crystal habits was directly related to the relative exposure of different crystal facets. Cohesion, determined by a uniaxial compression test, was also found to relate to surface energy of the powders. By employing a surface modification (silanisation) approach, the contribution from crystal shape from surface area and surface energy was decoupled. By “normalising” contribution from surface energy and surface area, needle shaped crystals were found to be ∼2.5× more cohesive compared to elongated plates or hexagonal cuboid shapes crystals.
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