Our former master student Jan-Willem Wiegman was elected today with the third price of the Cofely -TUDelft Energy Efficiency Award. In this award TUDelft master students compete for the brightest idea that can result in energy saving, CO2 reduction or increase the use of sustainable energy sources. He received the 2500 euro award for his master thesis work on Luminescent Solar Concentrators. Congratulations Jan-Willem!
Koen Hooning, one of our master students working on new materials for Luminescent Solar Concentrators (LSC) had been awarded the Delft Energy Initiative Research Grant 2013. The 12.000 euro award will be used to execute his research plan to turn our newly discovered luminescent powder materials into a waveguide that forms the basis of a high efficiency LSC demonstrator.
Subsurface light scattering in tissue can be fruitfully used when our trillion-frames-per-second camera is operated in reflection-mode. Only a small fraction of laser light directly reflects from the surface of a person’s skin. The majority of light will enter the tissue and undergo multiple scattering events before part of the light exits the skin again at another location. Reflected femtosecond laser pulses will therefore stretch out to several nanoseconds indicating that, depending on the type of tissue, re-emerging light reaches as deep as several millimeters to even centimetres. It appears possible to use light scattering of femtosecond pulses to obtain subsurface tissue images that cannot be obtained with continuous laser light.
A strong indication that subsurface information can be obtained using our trillion-frames-per-second camera, comes from the movie below, showing the inside of the applicant right arm as a function of time from 0 to 70 picoseconds after pulsed 100 femtosecond laser excitation with 750 nm light. While in the first 10 picosecond no veins can be seen, they show up clearly after about 20 ps. At later times more veins located deeper appear and broaden due to increased blurring as light scattering becomes more and more dominant.
Below are selected movie still frames at specific times 7 picoseconds apart. Click here for more.
This morning Jan Willem Wiegman and Erik van der Kolk were interviewed for Business News Radio featuring there published research on sustainable building integrated luminescent solar concentrators. You can find the full interview (in Dutch) hereunder.
On 5 July Jan Willem Wiegman is graduating from TU Delft with his research into power-generating windows. The Applied Physics Master’s student calculated how much electricity can be generated using so-called luminescent solar concentrators. These are windows which have been fitted with a thin film of material that absorbs sunlight and directs it to narrow solar cells at the perimeter of the window. Wiegman shows the relationship between the colour of the material used and the maximum amount of power that can be generated. Such power-generating windows offer potential as a cheap source of solar energy. Wiegman’s research article, which he wrote together with his supervisor at TU Delft, Erik van der Kolk, has been published in the journal Solar Energy Materials and Solar Cells.
Medical Imaging with the speed of light
Nothing is faster than light, yet we managed to see light travel millimeter by millimeter with a one-trillion-frames-per-second ultra high speed video camera build from a femto second laser and a streak camera. The imaging technique, devised by MIT researcher Raskar, may be useful in medical imaging with light.
Cheap, fast and easy visualization of breast or brain tissue with light within the near infrared (NIR) transparency window (600-1000 nm), is a holy grail in medical imaging because it does not depend on harmful radiation, radioactive substances, or bulky instrumentation. The clinical value of NIR imaging has so far been limited due to the strong inelastic scattering of light in tissue that causes serious image blurring. A challenging solution to the scattering problem is the use of pulsed light sources and time resolved detection of transmitted light because in that case only unscattered photons that go straight can be selected. The bottleneck of this time-of-flight or time-gated approach has been a limited temporal resolution (>100 pico seconds) and a too poor sensitivity.
We have constructed a one-trillion-frames-per-second video camera based on a streak camera and a femto second laser, that combines a 100 times higher time resolution (~1 ps) and photon counting sensitivity. In the movie below it is explained that the time-of-flight camera can fruitfully be used to image objects in strongly scattering media, much better than can be done with continuous laser light. We are developing this time-of-flight camera further by optimizing it for NIR optical imaging in order to (i) better understand light transport in strongly scattering media and (ii) to perform 2D and 3D image reconstruction of realistic tissue equivalent phantoms.