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Postdoc

David William Collinson

Research Interests

High performance polymers and their composites have wide ranging application in advanced and emerging material systems. The macroscale performance of these advanced materials is often defined by interfaces that induce nanoscale changes in the microstructure or molecular conformations (termed the ‘interphase’) of the polymer. Atomic force microscopy (AFM) is an experimental method that allows for probing surface mechanical properties at nanoscale resolution and extremely low forces, providing an avenue for direct characterization of complex polymer systems. However, it remains challenging to quantitatively characterize nanomechanical properties with AFM, especially on polymers and soft materials, and requires a detailed understanding of AFM operation and material behavior. My research aims to interrogate both the nanoscale mechanics of polymer composites and the way that we measure them with atomic force microscopy (AFM).

David_researchinterests

Nanomechanical characterization of complex soft polymer composites

The past two decades have seen atomic force microscopy (AFM) evolve from an experimental technique to probe simple surface topography to one that can spatially map nanoscale material properties with exquisite sensitivity and high resolution. However, the assumptions required for interpretation of nanoscale mechanical data on polymers and the lack of clarity on the best practices for the different modes limits the quantitative accuracy of AFM methods and the interpretation of mechanical data. The analysis of AFM data becomes even more complex when multiple phases are present in a sample which further convolute measurements and the interpretation of the output data. My research in this area demonstrates how to utilize complementary finite element analysis as well as other simulation methods to better interpret high resolution quasistatic and dynamic AFM in complex and idealised polymer systems where measured properties gradients are on a similar length scale to the tip contact radius.

Polymer mechanical properties and dynamics near attractive interfaces

In polymers, the interphase layer is a nanoscale (1-100 nm) region of polymer that appears in polymers near a confining surface with altered properties because of chemical and physical interactions between local polymer chains and the surface of a filler or substrate. The interphase layer is thought to be responsible for many of the enhanced mechanical, dielectric, transport, and thermal properties in a wide range of applications including thin films, microelectronics, and polymer nanocomposites (PNCs). AFM, with its high resolution, direct imaging capabilities, and large range of available timescales for probing dynamics and structure simultaneously can play a significant role in unentangling the polymer interphase. In my research AFM measurements of the interphase incorporates the use of complementary experimental and simulation techniques to:

1. Correlate changes in mechanical properties with associated changes in polymer chemistry or structure near the interface
2. Confirm that the local measurements are representative of the system at large.

This approach has allowed for highly sensitive, temperature dependent measurements of the interphase in glassy polymers near silica particles and substrates. In addition, carefully controlled experiments on the frozen-in structural heterogeneity of glassy polymers has also identified a connection between the strength of structural heterogeneity below Tg and the fragility of glass formation.

Experimental characterization of the process-structure-property relationship in additively manufactured polymers

Additive manufacturing refers to the collection of manufacturing techniques that produce parts from polymer or metal feedstock by successively building up layers of material to produce a three-dimensional part. Recent improvements have seen additive manufacturing with polymers extend into functional applications including aerospace and biomedical devices. Despite numerous parametric studies linking bulk mechanical performance and the weld strength to the manufacturing process, there has been little experimental work to connect the mechanical behaviour of additively manufactured parts to their underlying microstructure despite the complexity of polymers used in additive manufacturing techniques. In my research I apply nanomechanical AFM techniques in conjunction with bulk characterization methods to identify the role of microstructure on the performance of blended (ABS) and semicrystalline (PLA and PEEK) polymer systems manufactured with fused filament fabrication as well as other techniques.

Publications (*Co-first author)

  • Collinson DW, Nepal D, Zwick J, Dauskardt RH. (2022) Gas cluster etching for the universal preparation of polymer composites for nano chemical and mechanical analysis with AFM. Applied Surface Science, 599, 153954
  • Zhao O, Collinson DW, Ohshita S, Naito M, Nakano N, Tortissier G, Nomura T, Dauskardt RH (2022) Insights into the Mechanical Properties of Ultrathin Perfluoropolyether–Silane Coatings. Langmuir, 38, 20, 6435–6442
  • Collinson, DW, Von Windheim, N & Brinson, LC (2022) Direct evidence of interfacial crystallization preventing weld formation during fused filament fabrication of poly (ether ether ketone). Additive Manufacturing, 51, 102604
  • Collinson, DW, Kolluru, PV, Von Windheim, N & Brinson, LC (2021) Distribution of Rubber Particles in the Weld Zone of Fused Filament Fabricated Acrylonitrile Butadiene Styrene and the Impact on Weld Strength. Additive Manufacturing, 41, 101964
  • Collinson, DW, Sheridan, RW, Palmer MJ & Brinson, LC (2021) Review - Best practices and recommendations for accurate nanomechanical characterization of heterogeneous polymer systems with atomic force microscopy. Progress in Polymer Science, 119, 101420
  • von Windheim N, Collinson DW, Lauc T, Brinson LC, Gall K. (2021) The influence of porosity, crystallinity, and interlayer adhesion on the tensile strength of 3D printed polylactic acid (PLA) Rapid Prototyping Journal. 27, 7, 1327-1336.
  • Collinson, DW; Emnett HM; Ning JX; Hartmann, MJZ; Brinson, LC (2021) Functional tapered polymeric fibers for use as a biomimetic, tactile sensory device, Soft Robotics. 8, 1, 44-58
  • Collinson, DW*, Eaton, M. D.*, Shull, K. R., & Brinson, L. C. (2019). Deconvolution of Stress Interaction Effects from Atomic Force Spectroscopy Data across Polymer− Particle Interfaces, Macromolecules, 52(22), 8940-8955.
  • Song, J.*, Kahraman, R.*, Collinson, DW*, Xia, W., Brinson, LC, & Keten, S (2019). Temperature effects on the nanoindentation characterization of stiffness gradients in confined polymers. Soft Matter (cover article), 15(3), 359-370.
  • Collinson, DW, Hartmann, MJ, & Brinson, LC (2019). Processing methods and apparatus to manufacture a functional, multi-scale, tapered fiber from polymer filament, U.S. Patent Application No. 16/102,364.
  • Kolluru, PV, Eaton, MD, Collinson, DW, Cheng, X., Delgado, DE, Shull, KR, & Brinson, LC (2018). AFM-based Dynamic Scanning Indentation (DSI) Method for Fast, High-resolution Spatial Mapping of Local Viscoelastic Properties in Soft Materials. Macromolecules, 51(21), 8964-8978.
  • Nandy, K*., Collinson DW*, Scheftic CM, Brinson LC (2018) Open-source micro-tensile testers via additive manufacturing for the mechanical characterization of thin films and papers PloS one, 13(5).
  • Becker S, Collinson DW, Mansell E, Robertson J, Hannon A, Zorec B, & Pavselj N. (2014). Skin Electroporation: Test Cell Re-Configuration. New Zealand Medical Journal, 127(6)

Patents

  • Collinson, DW, Hartmann, MJ, & Brinson, LC (2019). Processing methods and apparatus to manufacture a functional, multi-scale, tapered fiber from polymer filament, U.S. Patent Application No. 16/102,364.

Conference Proceedings and Presentations

  • Collinson, DW, Dauskardt RH (2022). Utilizing self-assembled mesoporous metal oxide matrices as a platform for specific, isolated studies of polymer-surface adsorption and interactions. Materials Research Society Spring Meeting.

  • Collinson, DW, Dauskardt RH (2021). Direct probing of the interfacial hydrogen bonding and dynamics of PMMA confined in porous organosilicate using correlative scanning probe microscopy. Materials Research Society Fall Meeting.

  • Collinson, DW, Eaton, MD, Shull, KR., & Brinson, LC (2019). Deconvolution of Structural Effects in the Determination of Local Mechanical Properties from Atomic Force Microscopy. Society of Engineering Science Conference.

  • Collinson, DW, Eaton, MD, Kolluru, PV, Brinson, LC, (2018) Semi-quantitative de-convolution of the measured interphase in particle-matrix polymer nanocomposites, Society of Engineering Mechanics, International Student Paper Competition – Finalist.

  • Collinson, DW, Kolloru, PV, Brinson LC (2018) AFM Analysis of Polybutadiene distribution in the weld zones of FDM-printed ABS dog bones. ASME IMECE.

  • Collinson DW, Yang AE, Hartmann MJZ, Brinson LC. (2016) High Aspect-Ratio Tapered Whisker. Society of Engineering Science, Poster Presentation.

  • Collinson DW, Kolloru PV, Brinson LC. (2016) Experimental Characterization of Butadiene interphase in ABS after fused deposition modelling. Society of Engineering Science, Poster Presentation.

Awards

  • Ryan Fellowship (2015-2017)

  • Walter P. Murphy Fellowship (2015-2016)

  • Fulbright Science and Innovation Award (2015 - 2016)

  • John R Templin Fellowship (2015-2016)

  • Graduate Leadership and Service Award (2017)

  • University of Canterbury Masters Scholarship (2014 – 2015)

  • Australasian Institute of Metals Prize (2014)

  • Lyall Holmes Memorial Scholarship (2012)

Education

Ph.D., Northwestern University, Mechanical Engineering, 2020
M.E. University of Canterbury, Mechanical Engineering, 2016
B.E. (Hons) University of Canterbury, Mechanical Engineering, 2015

Contact

(224) 713 9139

Location

Durand Building, Rm. 111