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Thermal History Sensing Films and Particles

Technology #20150274

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Thermoluminescent MaterialThermoluminescent IntensityThermoluminescent Particles
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Researchers
Joseph Talghader, PhD
Professor, Department of Electrical and Computer Engineering, College of Science and Engineering
External Link (ece.umn.edu)
Managed By
Larry Micek
Technology Licensing Officer 612-624-9568
Patent Protection

Provisional Patent Application Filed
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Non-confidential Summary [PDF]

Luminescent Thermal History Sensors

Durable, thermoluminescent particles or films can record thermal history of manufacturing processes over the temperature range of 100°C to 500°C. Days or months before they are needed, the materials are irradiated with a deep ultraviolet or ionizing radiation source to fill their charge carrier traps. At any time afterwards, the irradiated particles may be either incorporated directly into the manufactured article or adhered as a surface film or coating prior to the manufacturing process. Additionally, they may be either reusable or single-use disposable depending on the process. When the particles are heated during the manufacturing process, some of the charge traps will empty. When the particles or films in/on/near a local region of the manufactured product are irradiated with a laser source, they luminesce with characteristic features that provide a comprehensive profile of the local thermal history of the item in terms of temperature and duration. The physical form and durability of the particles and films enable a wide variety of sensor formats, and because the sensing particles may be deployed throughout or across a manufactured article, a complete thermal history record for any location on the article is possible—especially important for wide area manufacturing.

Unique Use of Thermoluminescent Material

Currently, no passive thermal history sensing technologies exist that can be easily applied and removed from a surface, especially over the common 100°C to 500°C temperature range. While thermoluminescent materials have been used for many years to measure radiation dosage, their usage for temperature sensing differs in several ways. Radiation dosimetry fills the trapping states by exposure to radiation, whereas in temperature sensing, the trapping states are filled beforehand and the desired signal is luminescence indicative of the emptying of the trapping states during the heating process. Another important difference is that the particles are passive sensors and do not require any power source, as would conventional temperature data logging sensors.

BENEFITS AND FEATURES:

  • Can measure intensity and duration of heating, not just the peak temperature
  • Thermoluminescent particles provide passive sensing, which requires no power source
  • Thermoluminescent particles are extremely durable
  • Versatile sensor format enables recording thermal history in any location on an article
  • Can be embedded into or placed on the surface of a thermal process article
  • Deployable in a variety of disposable forms, such as a tape, tag, ink, coating, etc.

APPLICATIONS:

  • Reusable or disposable sensors
  • Wide width thermal manufacturing such as web-coating or printing
  • Temperature sensing
  • Food and beverage packaging
  • Chemical and materials processing
  • Disposable thermal sensing films, tapes, tags, etc.
  • Boilers, condensers ovens, heat exchangers or other thermal heat devices requiring passive detection of thermal history

Phase of Development - Proof of Concept