Surface breaking in lyotropic nematic liquid crystals induced by a magnetic field.

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics · 1999 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 4013

Study snapshot

PublicationPhysical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics · 1999

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

The twist deformation induced by a magnetic field H in a lyotropic liquid crystal is analyzed. Our results show the existence of three regimes for the surface deformation related to two critical values for the external magnetic field. The first, for low magnetic field, is an elastic one in which the surface deformation disappears when the field is removed. In a second regime, a permanent deformation of the lyotropic liquid crystal is induced by the distorting field. This regime is characterized by a threshold for H, called H(*)(c). In the third regime, the sample is uniformly oriented along H. Also this regime has a well defined threshold value, H(**)(c), and the alignment remains even when the distorting field is removed. To interpret the experimental data recently published, we proposed a phenomenological model according to which there is an elastic coupling between the surface layer of thickness l and the bulk. This elastic coupling has a saturation for a given value of the deformation of the bulk with respect to the surface layer.

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AI evidence extraction

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Study typeother

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

A magnetic field (H) induced twist deformation in a lyotropic nematic liquid crystal with three regimes separated by two critical field thresholds. At low fields deformation was elastic and disappeared after field removal; above a threshold H*(c) a permanent deformation occurred; above a higher threshold H**(c) the sample became uniformly oriented along H and the alignment persisted after field removal. A phenomenological model was proposed involving elastic coupling between a surface layer of thickness l and the bulk with saturation behavior.

Outcomes measured

twist deformation
surface deformation regimes
threshold magnetic field values (H*(c), H**(c))
permanent deformation/alignment persistence after field removal

View raw extracted JSON

{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": "magnetic field",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "twist deformation",
    "surface deformation regimes",
    "threshold magnetic field values (H*(c), H**(c))",
    "permanent deformation/alignment persistence after field removal"
  ],
  "main_findings": "A magnetic field (H) induced twist deformation in a lyotropic nematic liquid crystal with three regimes separated by two critical field thresholds. At low fields deformation was elastic and disappeared after field removal; above a threshold H*(c) a permanent deformation occurred; above a higher threshold H**(c) the sample became uniformly oriented along H and the alignment persisted after field removal. A phenomenological model was proposed involving elastic coupling between a surface layer of thickness l and the bulk with saturation behavior.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "lyotropic liquid crystal",
    "nematic",
    "magnetic field",
    "twist deformation",
    "surface breaking",
    "threshold",
    "phenomenological model",
    "elastic coupling"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1103/physreve.60.6847
PubMed: 11970605

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