Film creditsFeel is a process. Study the process.
A proposed track connecting flow, recovery and friction to a formulation’s application journey, without treating touch as proof of absorption.
Proposed research project | Scientific question, methods and next comparisons. Published study results are attributed to their original sources.
The user encounters more than one viscosity.
A formulation moves from rest to spreading to the layer left behind.
A material’s role changes through the application journey. At rest, a structure may help a formula remain where intended. During spreading, its response to shear affects work and distribution. After the motion stops, recovery and the deposited layer can alter drag, tack or coherence. One viscosity measured at one shear rate cannot describe all of those experiences. Our proposed track starts with the sensory or handling problem a formulation team needs to resolve.
The development question might be easier spreading without excessive running, less persistent drag, acceptable recovery or a change in the final layer. These aims can compete. We would connect a small set of mechanical observations to a defined application protocol rather than search for a universal score of pleasantness. The intended value is a comparison that helps a formulator choose what to change and shows an ingredient business which function its preparation could credibly contribute.
Examine the development decision
Feel is a process. Study the process.
Open the sequence to examine what a development decision needs.
Identify the exact preparation, its source, and the properties a second laboratory must be able to reproduce.
Explanatory geometry · no simulated or measured performance
Describe the flow over a relevant window.
Shear thinning is a behaviour to quantify, not a claim of better feel.
The proposed rheology record would state concentration basis, hydration history, temperature, geometry, gap and the shear protocol. We would examine wall slip, loading damage and the accessible measurement window before interpreting apparent viscosity. A flow curve could then show whether the material remains nearly Newtonian or changes resistance substantially as the imposed shear rate increases. The selected window should reflect the intended process as well as practical instrument limits.
A power-law approximation can summarise a bounded part of that curve through a consistency parameter and flow index. Its parameters depend on the fitted range; they should not be extrapolated automatically to rest or very high shear. Fehlberg and colleagues used measured shear-rate dependence in their analysis of finger-pad liquid spreading (Fehlberg et al., 2025). That provides a useful external methodological example, while our proposed preparation and matrix would require their own data.
The flow index describes shear-rate dependence over the fitted range; it is not a sensory rating.
- Shear stressPa
- Power-law consistency parameterPa sⁿ
- Shear rates⁻¹
- Flow indexdimensionless
- Apparent viscosityPa s
Model conditions. Empirical fit over a stated shear-rate window at stated temperature and composition. No yield stress, rest viscosity or high-shear asymptote is implied.
Look at what survives the application step.
Flow and structural recovery deserve different measurements.
We would examine whether a useful structure recovers after a defined deformation, and how sensitive that answer is to waiting time and prior history. Small-amplitude oscillation within an established linear window could provide storage and loss moduli at stated frequency; a deformation-and-recovery sequence could address a different practical question. A large storage modulus is not automatically desirable when it also makes spreading difficult.
The study would keep transient recovery, thixotropic history and possible irreversible changes separate. An up-and-down flow loop is informative, but its area depends on the protocol and does not establish a universal material constant. Where filament formation or stringiness matters, an appropriate extensional or break-up observation could complement shear measurements. We would select the method for the handling limitation rather than add every available test. A partner’s process history and acceptable application window would guide interpretation, with uncertainty retained when a short protocol cannot distinguish competing explanations.
A biological preparation. A useful applied layer.
Investigate how an authenticated biological polymer could contribute to the water response and behaviour of a deposited formulation film.
Friction belongs to a contact, not a jar.
Speed, load and substrate can change the comparison.
A friction coefficient describes tangential resistance relative to normal load in a defined contact. A change can reflect lubrication, surface interaction, contact geometry or the behaviour of the participating materials. The proposed instrumented comparison would therefore record substrate roughness, compliance, conditioning, deposited amount, speed and load. It would not equate a low coefficient with universal pleasantness or a high coefficient with poor formulation performance.
The primary study by Fehlberg and colleagues examined finger-pad spreading of fifteen liquids on one rough solid substrate, with eleven participants choosing varying speeds and forces (Fehlberg et al., 2025). Its central relevance is the need to include the application procedure in the comparison. Those observations are external data, not a Bio touch panel. They do not establish skin penetration, tactile disappearance or performance of a new ingredient in a finished cream.
The coefficient relates tangential resistance to normal force for the measured contact and protocol.
- Coefficient of frictiondimensionless
- Magnitude of tangential forceN
- Normal forceN
Model conditions. Forces refer to the same contact and sampling definition. A ratio of trial medians need not equal the median of instantaneous force ratios; preserve the source processing convention.
Published specimen data | Explore the original measurements
Choose the condition.
Inspect the response.
Move between flow, deformation and frequency. Keep the measured point, specimen and method together before choosing your next comparison.
25 °C | Roughened PP50/P2 parallel plates; MCR 302 | No sweep timing or replicate counts supplied in this file.
50 measured flow points. Select a condition to inspect its source row. No model or interpolated result.
Only measured domain values are plotted. Both axes use logarithmic display.
Requested 85.4 s⁻¹; observed 85.4 s⁻¹. The nearest measured point is selected by logarithmic distance. No interpolation or extrapolation.
- Measured shear rate
- 85.4 s⁻¹
- Derived apparent viscosity
- 1.43583 Pa s
- Original CSV row
- 10
The point needs
its method.
Apparent viscosity is derived as measured stress divided by positive measured shear rate. It is not a separately measured value or a fitted constitutive parameter.
Not provided in CSV/README; rows are within-sweep measurements, not independent materials.
Two external source specimens. Brand and material names identify the deposited specimens; they imply no endorsement, partnership or current product specification.
What would make
your comparison useful?
Compare independently prepared candidate and benchmark specimens at a pre-specified application-relevant shear condition, preserving process/rest history. Establish repeatability and uncertainty before a wider material claim.
Proposed next experiment | No study is commissioned or performed here. No yield stress, uncertainty interval or consumer efficacy is inferred.
Inspect all source rows in this selected sweep
| Source row | Shear rate (s⁻¹) | Shear stress (Pa) | Derived apparent viscosity (Pa s) |
|---|---|---|---|
| 3 | 154 | 149.99 | 0.973961038961039 |
| 4 | 153 | 145.74 | 0.9525490196078432 |
| 5 | 138 | 141.61 | 1.0261594202898552 |
| 6 | 126 | 137.59 | 1.091984126984127 |
| 7 | 114 | 133.68 | 1.1726315789473685 |
| 8 | 104 | 129.89 | 1.2489423076923076 |
| 9 | 94.3 | 126.2 | 1.3382820784729588 |
| 10 | 85.4 | 122.62 | 1.435831381733021 |
| 11 | 77.3 | 119.14 | 1.5412677878395862 |
| 12 | 69.7 | 115.76 | 1.660832137733142 |
| 13 | 62.8 | 112.48 | 1.7910828025477707 |
| 14 | 56.4 | 109.28 | 1.9375886524822696 |
| 15 | 50.5 | 106.18 | 2.1025742574257427 |
| 16 | 45.2 | 103.17 | 2.282522123893805 |
| 17 | 40.3 | 100.24 | 2.487344913151365 |
| 18 | 35.9 | 97.397 | 2.713008356545961 |
| 19 | 31.8 | 94.633 | 2.975880503144654 |
| 20 | 28.2 | 91.947 | 3.260531914893617 |
| 21 | 24.9 | 89.338 | 3.5878714859437753 |
| 22 | 21.9 | 86.803 | 3.963607305936073 |
| 23 | 19.2 | 84.339 | 4.39265625 |
| 24 | 16.7 | 81.946 | 4.906946107784432 |
| 25 | 14.6 | 79.62 | 5.453424657534247 |
| 26 | 12.6 | 77.361 | 6.139761904761905 |
| 27 | 10.9 | 75.165 | 6.895871559633028 |
| 28 | 9.29 | 73.032 | 7.861356297093649 |
| 29 | 7.93 | 70.959 | 8.948171500630517 |
| 30 | 6.71 | 68.946 | 10.275111773472428 |
| 31 | 5.65 | 66.989 | 11.85646017699115 |
| 32 | 4.72 | 65.088 | 13.789830508474576 |
| 33 | 3.92 | 63.241 | 16.132908163265306 |
| 34 | 3.22 | 61.446 | 19.082608695652173 |
| 35 | 2.62 | 59.702 | 22.787022900763358 |
| 36 | 2.11 | 58.008 | 27.491943127962088 |
| 37 | 1.68 | 56.362 | 33.548809523809524 |
| 38 | 1.32 | 54.762 | 41.486363636363635 |
| 39 | 1.02 | 53.208 | 52.16470588235294 |
| 40 | 0.773 | 51.698 | 66.87968952134541 |
| 41 | 0.575 | 50.231 | 87.35826086956523 |
| 42 | 0.419 | 48.805 | 116.47971360381862 |
| 43 | 0.3 | 47.42 | 158.0666666666667 |
| 44 | 0.209 | 46.075 | 220.45454545454547 |
| 45 | 0.14 | 44.767 | 319.76428571428573 |
| 46 | 0.0904 | 43.496 | 481.15044247787614 |
| 47 | 0.0559 | 42.262 | 756.0286225402505 |
| 48 | 0.0326 | 41.063 | 1259.601226993865 |
| 49 | 0.0179 | 39.897 | 2228.882681564246 |
| 50 | 0.00871 | 38.765 | 4450.631458094144 |
| 51 | 0.00373 | 37.665 | 10097.855227882037 |
| 52 | 0.00114 | 36.596 | 32101.754385964912 |
Combine rheology with the motion.
A model should explain which variables change the contact.
For their spreading experiment, the authors defined a Hersey number using the flow consistency, flow index, speed, normal force and estimated contact geometry. We would use that model to teach and examine the external dataset, while treating any transfer to another substrate or preparation as a separate hypothesis. Its estimated radii are part of the model, not measured anatomical facts for every participant.
The expression below is dimensionless when K uses pascal-based units and lengths use metres. In the acquired dataset, the exponent column is n minus one, so it must be converted before calculating this quantity. The separate parameter-file header has a unit inconsistency; our reproduction uses the SI prefactor supplied in the friction file and checked against the reported columns. This detail matters because an unnoticed factor of one thousand could create a persuasive but incorrect comparison (Fehlberg et al., 2025).
This combines measured trial speed and load with fitted shear behaviour and estimated geometry for the external experiment.
- Authors’ Hersey numberdimensionless
- Consistency in η=Kγ̇ⁿ⁻¹Pa sⁿ
- Median sliding speedm s⁻¹
- Flow index; source exponent column plus onedimensionless
- Estimated finger-pad curvature radiusm
- Estimated contact radiusm
- Median normal forceN
Model conditions. External authors used R=0.05m and R_s=0.005m as common estimates. Applicability to another contact, geometry, lubricant or evolving material needs a new assessment.
A real comparison can become more informative.
Keep the fitting population and method visible.
Our bounded secondary analysis preserves all 165 published participant–liquid trial medians. Only the 77 observations for the seven most viscous liquids enter the two power-law fits. Recalculation of viscosity and Hersey number matches the supplied columns to numerical precision. The original-scale descriptive R² is approximately 0.372 for viscosity alone and 0.889 for Hersey number; the local Hersey exponent is 0.563, while the paper reports 0.55 (Fehlberg et al., 2025).
The difference is retained rather than edited to resemble the publication. These fits are descriptive, in-sample comparisons; repeated observations from the same participants are not 77 independent people, and a better fit does not prove causation or predictive performance in another formulation. The practical lesson is to ask which application variables a proposed study is missing. We would carry that question into a Bio design, not transfer the published Stribeck curve as an ingredient performance guarantee.
Test the sensory question directly.
An instrument narrows the explanation; it does not replace the viewer.
A proposed sensory comparison would define the terms participants are asked to judge and the point in the application journey at which they judge them. Slipperiness, tack, residue and pleasantness are not interchangeable endpoints. Appropriate blinding, randomised presentation and control of dose and handling would help separate a material effect from expectation or order. Human participation would require an appropriate study process before recruitment.
Instrumented measurements could inform hypotheses about the observation, but a mechanical association should not become proof of a sensory mechanism. We would retain individual variation and use an analysis suited to repeated ratings where relevant. A formulation team would help define an acceptable outcome and the incumbent. If a candidate lowers friction but worsens tack or recovery, that trade-off belongs in the result. The intended deliverable is a defensible application comparison, including negative or ambiguous observations, rather than a universal promise of luxurious feel.
The next proposed comparison.
A preparation-specific film comparison, with loading, conditioning and a relevant reference.
Making the next formulation change easier to choose.
A useful texture package connects the curve with the application.
The proposed package would bring together preparation identity, flow and recovery records, contact conditions, friction observations and any separately justified sensory comparison. It would state where an instrumental response supports the target, where it conflicts with another requirement and which next change is worth making. A material might justify a narrower role than originally imagined; that can still be commercially useful if it solves a consequential formulation problem.
A formulator could bring the application protocol and existing alternative. An ingredient business could bring traceable lots and a proposed function. A rheology or tribology collaborator could help examine measurement fitness and interpretation. Scope, sample access, ethics where applicable, responsibilities and confidential information would be agreed before work begins. The investment logic is to establish a repeatable function in a defined use, with a comparison another team can understand, rather than to market an unexplained sensory adjective.
Polar-associated materials · Proposed development discussion
A development path
for this research.
Could this defined biological preparation contribute a useful deposited-film function in the intended formula?
The people this could serve.Skin-formulation scientists, biological-ingredient developers and research partners.
The decision behind the project.
Your intended application, present alternative and the constraint behind “Feel is a process. Study the process.”. A useful starting point is the change that would justify another development step.
A proposed scope centred on a preparation-specific film comparison brief and proposed evidence milestones.
Agree the comparison, acceptance basis and responsible expertise before discussing a paid package.
Specialist methods and a defined contribution.
Bring relevant analytical or experimental expertise, a comparator suggestion, and the conditions under which your method could resolve this question.
A jointly scoped proposal could connect your contribution with a preparation-specific film comparison brief and proposed evidence milestones.
Define contributions, required access, independent preparations and permitted outputs before work or protected information is shared.
The commercial purpose of the next milestone.
Bring the application or asset thesis, the buyer you expect to value it, and the scientific or commercial uncertainty that must be resolved before another commitment.
The proposed decision record would connect the buyer question with a preparation-specific film comparison brief and proposed evidence milestones. It would identify what a subsequent comparison needs to demonstrate.
Demand, development cost, resources, rights and a decision-changing milestone would need examination. No financing terms or investment outcome are represented here.
What a useful comparison
would record.
- Record stress or shear rate, temperature, geometry and the complete conditioning sequence.
- Retain flow or oscillatory observations over the application-relevant operating window.
- Compare the response after the defined deformation and recovery interval against a matched preparation.
What the proposed
brief could leave behind.
- A preparation-specific film comparison brief and proposed evidence milestones
- A preparation, comparator and endpoint record tied to this question.
- A source-linked account of the evidence gaps, study assumptions and next review point.
The proposed discussion brief
A brief you
can take away.
Use non-confidential notes to connect this topic with your own decision. Entries stay in this browser tab; saving creates a text file on your device. Nothing is submitted.
Begin with a scoped evidence or study-design discussion; experimental delivery would need separately agreed expertise, access and resources.
Notes are optional. The brief includes this page’s proposed question and public source links.
Proposed scope; resources, methods, rights and delivery terms would be agreed before work. Begin with non-confidential information.
Contact conditions
and the comparison.
Explore 165 published friction trial medians, with the fit populations, equations and method context beside the data.
Enter the tribology analysisSources and reading notes.
External work is identified below. Access notes describe the material inspected for this page; company research questions and proposed work are not presented as findings from these sources.
Fehlberg et al, 2025Fehlberg et al. (2025) A Touch of Stribeck - Finger-Pad Friction in Viscous Liquid Spreading
Primary finger-pad spreading study, power-law rheology and the authors’ Hersey-number formulation.
Scope and limitations: Eleven participants, fifteen liquids, rough solid substrate. No Bio experiment, cream disappearance, penetration or human skin-benefit outcome.
Open original sourceFehlberg et al, 2025Fehlberg et al. (2025) Dataset for A Touch of Stribeck - Finger-Pad Friction in Viscous Liquid Spreading
Published trial medians, rheology parameters and reproducible bounded secondary analysis.
Scope and limitations: CC BY4.0. Only four named files acquired in this pass. Local exponent0.563 differs from paper0.55; repeated participants limit independent inference.
Open original sourceYang et al, 2025Yang et al. (2025) Influence of Processing and Stabilizer Selection on Microstructure, Stability and Rheology of Emulsion-Based Semisolid Formulations
Primary controlled semisolid processing/stabilizer study using microscopy, rheology, calorimetry and accelerated separation.
Scope and limitations: Propylene-glycol droplets in mineral oil with glyceride stabilisers. Not an EPS cream, microbial challenge, Bio manufacturing capability or universal shelf-life model.
Open original source