Paper Number
PF3 

Session
Applied Rheology for Pharmaceuticals, Food and Consumer Products

Title
Toward an understanding of psychorheology through transient recovery rheology

Presentation Date and Time
October 12, 2022 (Wednesday) 4:25

Track / Room
Track 2 / Sheraton 3

Authors (Click on name to view author profile)

  1. Burgeson, Eric M. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
  2. Martin, Jeffrey (Johnson & Johnson, Consumer Inc.)
  3. Jogan, Matjaz (Johnson & Johnson, Consumer Inc.)
  4. Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Eric M. Burgeson1, Jeffrey Martin2, Matjaz Jogan2 and Simon A. Rogers1
1Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 2Consumer Inc., Johnson & Johnson, Skillman, NJ 08558

Speaker / Presenter 
Burgeson, Eric M.

Keywords
experimental methods; consumer products

Text of Abstract
Soft materials are commonly used in consumer products such as food, hygiene products, cosmetics, and toys. An ideal product will be enjoyable to use and touch, necessitating an ability to design material properties. However, perception is difficult to quantify and design for due to its inherent subjectivity. The goal of the present work is to develop characterization techniques that link the subjective realities of perception of soft materials to reproducible, physics-based measurements. That is, we seek to understand the psychorheology. While conventional rheological practice often emphasizes steady-state measures, human perception is rapid and transient, and better corresponds to rheology of timescales no longer than a few seconds. We present results from an industrial scale human perception panel that allows us to identify typical timescales over which people form perceptions of standardized therapy putties. We show that most participants intuitively perform creep and recovery tests on timescales around a second, indicating the importance of both aspects of rheological testing. Inspired by the human perception results, we perform non-steady-state recovery rheology experiments that decompose transient strains into recoverable and unrecoverable components. The strain components are related to the bulk behaviors of deformation and elastic recovery that one experiences while touching viscoelastic materials. The strain components are tracked with respect to two independent timescales – a creep time and a recovery time – that allow us to build a transient view of traditional rheological metrics at perception-relevant times. Instantaneous material properties are found to change rapidly and scale logarithmically, suggesting that timescales play a large role in perception. This work shows the importance of non-traditional transient rheological measures in understanding psychorheology and provides motivation for recovery rheological studies of other consumer products.