Particle Engineering: Building Structure for Functionality IFPRI Workshop June 14-15, 2013

Workshop Objectives Identify and share best practice for backwards product design related to (a) strength/attrition and (b) dispersion/disintegration, and (c) flow properties; Identify and share current best approaches to product modeling and model validation related to (a) strength/attrition and (b) dispersion/disintegration and (c) flow properties; Develop a list of the key open questions (grand challenges) the academic community should be addressing in this area; Propose a road map for industry/academia/government collaboration to address these questions.

Workshop Structure Panel Discussion: barriers to first-principles design of particles for function Three Breakouts: – Common issues across industry sectors – Experimentally characterizing structure and its relationship to function – Modeling particle function Whole workshop discussion: pull it all together & develop path forward

Leading Questions Process Models? – Do you design your particles with the end in mind? Or do you just take what nature gives you? – Do you have issues with the process technology used to produce the desired particle structure? If yes, what are these issues? Product Models: – What properties are most important to you when you do particle design? – Do you have a firm grasp on the relationship between the functional expectations and the particle structure? If no, where usually is the gap? Have you had any colossal failures as a result of a poorly designed particle (that you are willing to talk about)? Particle design is usually done at the interfaces between many disciplines (chemical engineering, physics, chemistry, physical chemistry, mechanical engineering, biology, etc.). Do you routinely bring all parties to the table?

Breakout Ground Rules Each group has a facilitator (Neda, Karl, Judith) and a scribe (Jennifer, Steven, Ridade) Each group needs to choose someone to report back (can be different each session) – use flipcharts One company representative per group Evenly distribute academic and industrial representatives between groups

Summary of Key Points for breakout 1 We don’t often use product models to predict performance or to design particulate products – We agree with the material science construct: (formuatlion)-process- structure-function – Human/organization barriers (formulation scientist, process engineer) We need to describe and measure single particle distributions – The sting is in the tail – Also need distributions of interactions (at the surface) Missing of meso-structure link to relate primary properties to macroscopic properties – Input of probability distributions of particle properties – Definition of correct length & time scales to measure structure (aggregates of aggregates of aggregates…) – Development of structure throughout the process (history is important) Decision tree to define required characterization and modeling would be helpful to sell product modeling to industry – Need to be phenomologically based

Break out 2 Characterization There’s a general understanding of what tests are available but very few standard tests Challenge 1: How to efficiently measure distributions of single particle properties other than size, – Shape, strength, roughness, adhesion force, surface energy ….? – Many Single particle vs emsemble measurements?? Need a model to interpret data. Challenge 2: How do we measure structure? – At correct length scales? – As a function of process and history (in situ?) – Distribution of structure – what are the descriptors? Challenge 3: Why do we do macroscopic product tests? – To identify the controlling phemenon – To quantity the controlling phenomenon (rate constant, property) – ”to get a number” index of performance for comparison or ranking Challenge 4: Macroscopic tests often have several phenomena occuring and/or unknown and uncontrolled stress and strain field (and geometry) – Shear cell, mechanical properties of standard geometries are “good” tests – Many others are not eg. inermediate flow

The way forward? Recommendations to IFPRI for future research projects? Perspectives article in Powder Technology? White paper/presentation to government funding agencies? What else?

Workshop Files Archive Long term: IFPRI AGM 2013 AGM Outputs web page Short term: ftp.ifpri.netftp.ifpri.net – Username: AGM2013 – Password: – Both are case sensitive

Research Questions How do we describe structure on different length scales? – Kohlus (sp?) work relevant here Besides incipient flow, how do we measure flow characteristics? – General theory is lacking in this area

Research Questions from Breakout 1 Which properties at which length (and time) scales need to be described to understand powder structure effects? – Interactions and surface effects of individual particles poorly understood How do we measure / incorporate property distributions of single particles and/or particle assemblies? Can IFPRI develop a decision tree in order to aid decisions on which properties are necessary to measure to model final properties?