#90 speculative candidates — version4

Ranks are subjective editorial priorities, not empirical findings.

1. S4-0039 A spring-coupled pair of sliders should compute a weighted average position under quasistatic loading.
Test: Compare equilibrium with input positions.
Contrary: Friction prevents the predicted average.

2. S4-0123 A vibrating aperture should estimate a beam's local intensity gradient from its first harmonic.
Test: Scan known beam profiles.
Contrary: Harmonic output follows intensity alone.

3. S4-0210 A patterned void array should make an impact pulse split into two delayed arrivals.
Test: Measure transmitted waveforms.
Contrary: Only one broadened pulse appears.

4. S4-0307 A moving contact line should sort inert particles by rolling versus sliding mobility at equal size.
Test: Track calibrated particles.
Contrary: Mobility does not predict deposition position.

5. S4-0414 A bistable oscillator should retain the order of two impulse magnitudes in its final state.
Test: Reverse paired impulses.
Contrary: Order does not affect state.

6. S4-0616 A rotating slotted conductor should produce distinguishable drag signatures for surface and through-thickness cracks.
Test: Scan known defects.
Contrary: Signatures overlap.

7. S4-0731 A porous chamber wall should reveal absorbed moisture through a changed pressure-relaxation tail.
Test: Control moisture loading.
Contrary: Tail is dominated by leaks.

8. S4-0849 A self-equalizing clamp should reduce dimensional error after unclamping a thin workpiece.
Test: Measure before/after geometry.
Contrary: Equal forces do not reduce springback.

9. S4-0012 A shaped pulley should transform a sinusoidal input into a nearly triangular displacement waveform.
Test: Measure output against the kinematic design.
Contrary: Waveform distortion remains large.

10. S4-0001 A rotating shutter with logarithmic openings should turn constant-speed rotation into an exponential illumination ramp.
Test: Measure transmitted power versus angle.
Contrary: Ramp deviates from the calculated profile.

11. S4-0007 A buckling strip should perform a mechanical exclusive-or operation when opposing inputs cancel its snap trigger.
Test: Apply all input pairs.
Contrary: The truth table fails.

12. S4-0018 A two-track mechanical integrator should estimate the product of applied force and displacement without electronic sensing.
Test: Compare indicated work with calibrated loading.
Contrary: Output follows force or displacement alone.

13. S4-0024 A passive optical sorter should route equal-size particles by refractive index through calibrated radiation pressure.
Test: Track inert calibration particles.
Contrary: Routing follows size or convection alone.

14. S4-0032 A folded cable guide should route tension around an obstacle with less cross-talk between adjacent tendons.
Test: Measure induced neighbor motion.
Contrary: Cross-talk remains equal.

15. S4-0044 A fluidic bridge should compute a pressure difference using free-surface heights without net through-flow.
Test: Apply controlled pressures.
Contrary: Capillary bias prevents differential calibration.

16. S4-0055 A rotating acoustic mirror should encode sound arrival direction as a modulation phase.
Test: Apply known source directions.
Contrary: Phase is ambiguous under reflections.

17. S4-0067 A twisted plate should rotate its principal compliance direction continuously under axial tension.
Test: Measure stiffness tensor.
Contrary: Direction remains fixed.

18. S4-0086 A crossed pulley system should compute a displacement difference with reduced sensitivity to cable stretch.
Test: Apply known inputs and tensions.
Contrary: Stretch error remains large.

19. S4-0096 A mechanical parity checker should flag one missed step in a cyclic indexing train.
Test: Introduce controlled skipped steps.
Contrary: Checker returns a false normal state.

20. S4-0101 A phase-stepped shadow mask should estimate translucent-sheet thickness while rejecting uniform illumination drift.
Test: Measure calibrated sheets.
Contrary: Thickness estimates remain intensity-dependent.

21. S4-0111 A rotating crossed-polarizer mount should detect stress anisotropy independently of sample thickness using harmonic ratios.
Test: Test calibrated transparent plates.
Contrary: Thickness changes mimic anisotropy.

22. S4-0124 A capillary liquid lens should reject small pressure noise when its contact line sits in a geometric recess.
Test: Measure focal jitter.
Contrary: Recesses increase stick-slip jitter.

23. S4-0137 A paired cavity path should distinguish gas-pressure changes from window deformation through opposite optical sensitivities.
Test: Vary pressure and mechanical window loading.
Contrary: Responses remain degenerate.

24. S4-0145 A passive mirror stack should expose individual layer displacement through separate echo-like optical path peaks.
Test: Move known layers.
Contrary: Peaks cannot be uniquely assigned.

25. S4-0158 A vibrating optical window should shed droplets at lower amplitude when driven in a traveling-wave mode.
Test: Measure clearing thresholds.
Contrary: Standing-wave drive clears equally well.

26. S4-0169 A folded optical lever should amplify displacement while preserving a compact detector spot excursion.
Test: Measure sensitivity and range.
Contrary: Amplification forces equal range loss.

27. S4-0184 A compliant optical window should reduce stress birefringence through a sliding perimeter support.
Test: Measure polarization distortion under pressure.
Contrary: Sliding does not reduce birefringence.

28. S4-0198 A transparent shear cell should expose wall slip through different motion of surface and interior optical markers.
Test: Measure controlled slip.
Contrary: Marker motion cannot resolve the difference.

29. S4-0203 A hollow strut should retain load after local crushing through outward deployment of an internal fold.
Test: Compress instrumented struts.
Contrary: Fold deployment causes global collapse.

30. S4-0212 A constrained foam should expand laterally into a reserve pocket and delay densification.
Test: Measure force and volume distribution.
Contrary: Reserve storage does not delay force rise.

31. S4-0225 A corrugated seal support should maintain contact after local edge damage through neighboring-ridge recruitment.
Test: Measure leak pressure.
Contrary: Damage creates an unrecoverable leak.

32. S4-0237 A spring network should display a measurable directional wave-speed difference after asymmetric prestressing.
Test: Measure bidirectional pulses.
Contrary: Difference vanishes after correcting tension.

33. S4-0246 A prestretched membrane should recover its original tension after local heating through a sliding perimeter reservoir.
Test: Measure tension after cooling.
Contrary: Tension changes permanently.

34. S4-0259 A curved interface should reduce adhesive-free joint slip by increasing normal force under shear.
Test: Measure force components.
Contrary: Shear decreases normal contact.

35. S4-0271 A segmented membrane backing should limit the area affected by a local puncture.
Test: Map deformation after puncture.
Contrary: Damage propagates across segments.

36. S4-0287 A twisted beam pair should cancel extension under applied torque while preserving rotation.
Test: Measure coupled motion.
Contrary: Axial displacement remains large.

37. S4-0299 A porous elastic layer should reveal trapped liquid through a slower recovery mode after compression.
Test: Compare dry and known wet states.
Contrary: Recovery modes remain indistinguishable.

38. S4-0301 A drying liquid bridge should concentrate benign solute at its narrowest section before rupture.
Test: Map dye concentration.
Contrary: Solute accumulates only at the edges.

39. S4-0315 A capillary droplet train should maintain separation after gentle compression through trapped-air cushions.
Test: Measure collision frequency.
Contrary: Air cushions collapse and droplets merge.

40. S4-0326 A liquid bridge should distinguish surface contamination from roughness through different relaxation after a small oscillation.
Test: Test controlled surfaces.
Contrary: Relaxation signatures overlap.

41. S4-0339 A crystallization front should slow before meeting an impermeable obstacle because local solute redistribution changes supersaturation.
Test: Image front speed.
Contrary: Speed changes only at contact.

42. S4-0348 A porous wick should resist contamination-induced flow collapse when alternate pores remain unwetted until needed.
Test: Measure flux after controlled fouling.
Contrary: Reserve pores fail to activate.

43. S4-0357 A capillary trap should release trapped gas under vibration only when the gas volume exceeds a geometric threshold.
Test: Measure escape conditions.
Contrary: Small and large pockets escape equally.

44. S4-0368 A drying suspension should produce a more uniform deposit when its support slowly changes curvature.
Test: Map inert deposit thickness.
Contrary: Curvature changes worsen nonuniformity.

45. S4-0380 A crystalline coating should delaminate more controllably when a patterned weak boundary guides the front.
Test: Map benign salt release.
Contrary: Front ignores the boundary.

46. S4-0395 A foam film should reveal local contamination through an asymmetric response to a small shear oscillation.
Test: Apply controlled benign contaminants.
Contrary: Response is not contamination-specific.

47. S4-0402 A pendulum with a moving pivot should reduce sensitivity to support-height changes through geometric compensation.
Test: Measure period across heights.
Contrary: Compensation fails.

48. S4-0417 A rotating cavity containing a loose disk should reveal an internal obstruction through phase-slip bursts.
Test: Introduce controlled obstructions.
Contrary: Bursts occur equally without obstruction.

49. S4-0429 A rolling polygon should encode surface roughness in the statistics of its dwell angles.
Test: Test known surfaces.
Contrary: Statistics reflect only polygon geometry.

50. S4-0438 A rolling shell should estimate liquid fill fraction from the difference between start and stop torques.
Test: Test known fills.
Contrary: Difference is dominated by bearing friction.

51. S4-0447 A hinged inertial mass should trigger differently for equal-impulse pulses of opposite temporal skew.
Test: Apply time-reversed pulses.
Contrary: Trigger probability is unchanged.

52. S4-0459 A coupled oscillator should reveal a friction change through asymmetric energy exchange between modes.
Test: Vary one joint friction.
Contrary: Asymmetry is not friction-specific.

53. S4-0471 A suspended mass should estimate the duration of an acceleration pulse from its post-pulse orbit shape.
Test: Apply calibrated pulses.
Contrary: Orbit depends only on impulse.

54. S4-0483 A suspended oscillator should estimate support compliance from its amplitude-dependent resonance splitting.
Test: Vary known support stiffness.
Contrary: Splitting is dominated by drive nonlinearity.

55. S4-0498 A rolling ring should reduce orientation sensitivity to floor slope through a moving internal ballast.
Test: Measure steady orientation.
Contrary: Ballast increases slope sensitivity.

56. S4-0503 A compliant thread should distribute screw load across more engaged turns.
Test: Measure turn-by-turn strain.
Contrary: The first turn still carries most load.

57. S4-0514 A compliant pin should signal wear through a measurable shift in lateral stiffness before clearance grows visibly.
Test: Abrade calibrated pins.
Contrary: Stiffness signal appears too late.

58. S4-0527 A rolling contact should reveal a hidden surface step through an asymmetric force pulse.
Test: Traverse calibrated steps.
Contrary: Pulse cannot distinguish height from speed.

59. S4-0536 A rolling cam follower should retain contact during rapid return through a passive auxiliary inertial mass.
Test: Measure follower separation.
Contrary: Mass increases separation.

60. S4-0548 A compliant screw seat should limit tightening torque without permanent deformation.
Test: Measure torque-angle loops.
Contrary: Limiting requires plastic damage.

61. S4-0562 A compliant bearing seat should isolate high-frequency shaft motion while maintaining static alignment.
Test: Measure transfer and alignment.
Contrary: Isolation introduces unacceptable runout.

62. S4-0574 A rolling support should detect local surface compliance through contact-time asymmetry.
Test: Traverse calibrated soft patches.
Contrary: Roughness creates identical asymmetry.

63. S4-0589 A floating torque sensor should reject bending moments through a freely aligning contact ring.
Test: Apply combined loads.
Contrary: Bending cross-talk remains high.

64. S4-0600 A compliant bearing liner should warn of approaching seizure through an amplified temperature-gradient displacement.
Test: Measure motion and friction.
Contrary: Warning appears after seizure begins.

65. S4-0602 A suspended magnet should distinguish a conductive plate edge from a crack through the spatial width of damping changes.
Test: Scan known features.
Contrary: Widths overlap.

66. S4-0613 A conductive mesh should detect a broken strand through rotation-dependent impedance anisotropy.
Test: Break known strands.
Contrary: Anisotropy is below baseline variation.

67. S4-0625 A conductive liquid-free contact should reveal oxidation through a rate-dependent mechanical damping change under magnetic excitation.
Test: Age controlled contacts.
Contrary: Damping is not oxidation-specific.

68. S4-0638 A suspended magnetic blade should detect particle accumulation through its angular resonance rather than static deflection.
Test: Add calibrated ferrous particles.
Contrary: Resonance changes are not monotonic.

69. S4-0647 A suspended loop should distinguish magnetic torque from thermal expansion through opposite response under current reversal.
Test: Measure reversed-current traces.
Contrary: Thermal transients mimic torque symmetry.

70. S4-0658 A flexible magnetic shutter should reset using stored elastic energy after field removal.
Test: Cycle switching.
Contrary: Remanence prevents reliable reset.

71. S4-0674 A flexible magnetic coupler should self-align before carrying substantial torque.
Test: Measure alignment and torque timing.
Contrary: Torque rises before alignment.

72. S4-0688 A passive inductive bridge should detect partial contact between overlapping metal sheets through changing current paths.
Test: Vary contact area.
Contrary: Oxide variability prevents calibration.

73. S4-0699 A flexible magnetic target should indicate distributed pressure through a changing multipole field.
Test: Apply known loads.
Contrary: Different pressure maps yield identical fields.

74. S4-0703 A porous gas diffuser should reduce flow maldistribution when its upstream chamber changes shape under pressure.
Test: Map outlet velocities.
Contrary: Deformation worsens maldistribution.

75. S4-0715 A flexible gas bag should maintain a fixed optical sampling thickness using a tensioned internal spacer.
Test: Measure path length over volume.
Contrary: Spacer buckles or distorts the path.

76. S4-0728 A passive vent should close before a rising liquid reaches its gas outlet through buoyancy-amplified motion.
Test: Measure closure timing.
Contrary: Liquid enters before closure.

77. S4-0739 A rotating vent should shed condensed droplets centrifugally while preserving gas-flow resistance.
Test: Measure droplet removal and resistance.
Contrary: Removal requires excessive rotational drag.

78. S4-0751 A passive relief valve should reopen less violently when a compressible side pocket stores its closure impulse.
Test: Measure valve acceleration.
Contrary: Pocket increases rebound.

79. S4-0765 A porous vent membrane should reveal incipient wetting through a sharp change in gas-flow noise.
Test: Control liquid contact.
Contrary: Noise changes only after full blockage.

80. S4-0777 A sealed pressure chamber should detect an internal flexible obstruction through nonlinear compression response.
Test: Insert calibrated membranes.
Contrary: Response is indistinguishable from gas-volume change.

81. S4-0789 A passive pneumatic latch should tolerate slow supply decay while responding to rapid intentional depressurization.
Test: Apply pressure histories.
Contrary: Decay and reset cannot be separated.

82. S4-0800 A flexible vent should return to its initial conductance after repeated wetting and drying.
Test: Measure flow cycles.
Contrary: Residual liquid changes conductance permanently.

83. S4-0802 A compliant molding insert should release undercut shapes through sequential inversion without damaging the part.
Test: Measure release force and defects.
Contrary: Inversion tears the part.

84. S4-0816 A passive tensioner should keep film tension stable as a supply roll's diameter decreases.
Test: Measure tension through payout.
Contrary: Tension follows roll radius.

85. S4-0827 A flexible support grid should reveal uneven vacuum holding through a visible shape pattern.
Test: Apply controlled suction leaks.
Contrary: Pattern cannot localize weak holding.

86. S4-0838 A rotating drying rack should reduce thickness gradients in a benign liquid coating through gravity averaging.
Test: Measure final film.
Contrary: Rotation creates circumferential bands.

87. S4-0853 A rotating mold should suppress one-sided bubble accumulation during benign liquid casting.
Test: Image void distribution.
Contrary: Rotation traps a central gas core.

88. S4-0867 A flexible stencil should release deposited features with less lateral drag through out-of-plane curling.
Test: Measure feature displacement.
Contrary: Curling increases distortion.

89. S4-0878 A rotating powder distributor should compensate hopper depletion through a moving gravity reference.
Test: Measure delivered mass.
Contrary: Dose still falls with fill level.

90. S4-0891 A passive assembly latch should reject debris-induced false seating through a second independent contact condition.
Test: Add inert debris.
Contrary: Debris satisfies both conditions.