Three-dimensional three-interval thixotropy test (3D-3ITT) protocol for cosmetic lotions: A proof-of-concept study...

To introduce a novel method that explores the relationship between sensory perception during the cosmetic application journey and measurable physical parameters. We establish a three-dimensional, three-interval thixotropy test (3D-3ITT) protocol that maps 'shear dose' (rate × duration) to structural recovery, and test whether this fingerprint associates with sensory and emotional responses during use.

Four formulations were prepared as two pairs: serum-like (S1s/S2s) and watery-lotion (S1w/S2w), using two thickeners at higher vs. lower concentrations to reach target viscosities. From 3D-3ITT recovery maps, we computed an equal-weighted early-time thixotropy index (TI_3D). In a subsequent consumer study (N = 30), untrained participants completed randomized, contralateral half-face application of each pair and a questionnaire assessing sensory attributes and emotions.

3D-3ITT clearly differentiated the four samples. Formulations primarily thickened with Alcaligenes polysaccharides (S1s/S1w) showed markedly greater sensitivity (higher TI_3D) to shear dose than those thickened with Xanthan gum (S2s/S2w), with TI_3D values of 46 (S1s), 37 (S1w), and 5.8 for both S2s and S2w. In consumer testing, the high-TI_3D formulations were generally rated as more easily absorbed and less sticky or greasy, with the clearest sensory differences concentrated in application phase attributes. In the serum pair, the high-TI_3D formulation (S1s) produced significantly more favourable emotional shifts, including lower Anxiety and higher Relax, Comfort and Overall Emotional State. Across both paired studies, larger positive sensory shifts were modestly yet significantly associated with larger positive emotional shifts at the subject level. Overall, thixotropy captured by TI_3D provided more insight and separation than conventional rheological metrics.

3D-3ITT provides a compact, usage-relevant recovery landscape and a single actionable index that may help relate laboratory metrics to consumer-relevant sensory and emotional responses. In this four-formula proof-of-concept set, TI_3D differentiated textures more sensitively than single-point rheology and was consistent with a cautious interpretation of a TI_3D-sensory-emotion pathway. Practically, this supports rapid A/B down-selection, targeted polymer/process tuning, and further exploration of how laboratory metrics relate to perceivable sensory experience.