Inexpensive Humidity Sensitive Polymer Hologram
Dublin Institute of Technology (DIT) is seeking companies to license a novel inexpensive hologram which changes colour as the humidity of its environment changes. It can be used in many applications including intelligent packaging and product authentication. Currently humidity indicator cards record humidity from 5 to 90 percent in 10 percent increments. However there are several limitations; the colour range is limited to only two or three colours, the response time to show changes in humidity is slow taking up to a few hours and a colour key is needed to interpret the reading. The typical size of a card is 1cm so there is limited space for graphics.
Researchers at DIT have developed a unique humidity indicator in the form of a low cost lightweight polymer hologram (30–70 μm) which is easily incorporated into packaging and graphics (logos, text, numerical data and three dimensional images). Graphics can be designed to change with humidity so information is displayed directly without the need for a colour key. The indicator is easily read and involves a colour change over a broad colour spectrum. One small hologram can cover the entire humidity range. The speed of response can be adjusted to suit the application with fast response times of a few seconds useful for security applications. Detecting the humidity range from 20 – 90 percent is useful for high value products which are sensitive to humidity, especially during transit.
Applications
- Humidity indicator - the hologram gives a very accurate measurement of the level of humidity in the range of 20-90 percent.
- Intelligent packaging – sensing the environment in packaging and consumer goods; food, cosmetics, pharmaceutical or electronics.
- Security/authentication – when you breathe on the hologram it changes colour quickly, this is useful for certi-cation and brand protection.
Advantages
- Inexpensive - a lightweight polymer hologram is 30 –70μm thick and is easy to fabricate making for low cost.
- Holographic images – a variety of forms including logos, text, 3D images, and numerical data can be displayed and change when humidity levels change.
- Enhanced performance;
- Humidity measurement - measurement of the humidity in the range 20-90 percent.
- Quick response time – colour change in only a few seconds.
- Ease of fabrication – the hologram is produced in a self-developing photopolymer; only light exposure is required with no chemical or physical processing.
- Broad colour spectrum - the indicator is easily read over a wide range of colour.
Technology Description
This inexpensive Holographic Humidity Sensor measures the level of humidity in a package. It works on the principle that the hologram expands when it absorbs moisture increasing the spacing between the fringes in the hologram and thereby shifting the colour of the hologram towards the red end of the spectrum. Loss of moisture has the opposite effect, so a green hologram will turn red in high humidity and blue in low humidity.
Stage of Development
Dublin Institute of Technology has -filed a patent, developed a prototype and continues research in this area.
Dr. Izabela Naydenova
Dr. Naydenova is a lecturer in physics at DIT. She holds a Ph.D. in Physics from the Bulgarian Academy of Sciences. Her research interests include holographic recording materials, sensors, optical data storage of information and polarization holography. Izabela has published more than 40 papers on holographic recording materials and holographic applications and is co-author of seven patent applications.
Dr Suzanne Martin
Dr. Martin is Centre Manager of IEO. She holds a Ph.D. in Physics from Trinity College Dublin and her doctoral research work involved the optimisation and characterisation of a new polymeric holographic recording material for use in holographic interferometry and the manufacture of holographic optical elements. She has published more than 40 papers on holographic recording materials and holographic applications and is co-author of nine patent applications.
Prof. Vincent Toal
Prof. Toal is Head of the School of Physics at DIT and Executive Director of the Centre for Industrial and Engineering Optics (IEO). He holds a PhD in Electronic Engineering from the University of Surrey. He has published more than 60 papers and is co-author of nine patent applications.
Dr. Raghavendra Jallapuram
Dr. Jallapuram is currently working as a Postdoctoral Research Fellow in IEO Centre. Raghavendra other research interests include Electronic Speckle Pattern Interferometry and display holography.
Former DIT Researcher Hosam Sherif is a co-inventor.
The Centre for industrial & Engineering Optics (IEO)
The IEO is a research centre in DIT’s School of Physics specialising in holography and holographic materials development, interferometric systems and devices and optical profilometry.
