Chocolatiers, like Morphotonix in Switzerland, have already demonstrated holographic effects on chocolate that are created directly from the injection-moulded or thermo-formed chocolate plastic moulds. They give the chocolate surface a specific controlled roughness that diffracts the light and makes it shiny.
‘But beyond aesthetics, holograms on food – specifically, edible holograms – could be used to reduce packaging needs, for example, as information about nutritional content, or labels could be printed directly onto the food item,’ Dr. Haider Butt, an associate professor in the Department of Mechanical Engineering at Khalifa University said. ‘To that end, we developed a quick and low-cost fabrication method for producing holograms on corn syrup films.’
The researchers have recently published their findings in ANC Nano (American Chemical Society)*.
Butt and his team used holographic direct laser interference patterning (DLIP) – a direct, simple, low cost and rapid technique that requires only one processing step and doesn’t require masks or templates. They developed a DLIP method to directly pattern one-dimensional nanostructures on edible substrates (dried films of corn syrup).
The holographic pattern created by this method depends on the number of interfering beams and their incident angles, polarisation, and intensity. The team notes that hologram surfaces diffracted a wide range of visible wavelengths depending on the tilt angle of the hologram with respect to the incident light.
The researchers deposited a thin layer of synthetic black dye (900 nm thickness) onto the corn syrup thin film in order to maximise the laser pulse absorption. This enabled the ablation process (which removes a significant portion of the black dye) to generate low-cost nanostructures on the surface of the corn syrup film.
‘Currently our work is limited because of the usage of commercial synthetic black dye,’ says Butt. ‘In the future, we will use food-grade dyes and optimise the pulsed laser’s parameters accordingly for producing edible holograms.’
These edible holograms could find applications in areas of food safety, for instance as sensors for harmful bacteria or to monitor food quality and shelf life. Since the holograms can be used to print for instance nutritional information directly onto food items, they could also reduce the need for packaging materials.
The researchers point out that a thorough future study is needed to quantify the shelf life of these holograms in different storage conditions. They also need to investigate the effects of temperature and moisture on the corn syrup.
* Direct Printing of Nanostructured Holograms on Consumable Substrates
Bader AlQattan, Joelle Doocey, Murad Ali, Israr Ahmed, Ahmed E. Salih, Fahad Alam, Magdalena Bajgrowicz-Cieslak, Ali K. Yetisen, Mohamed Elsherif, and Haider Butt
ACS Nano Article ASAP