Difference between revisions of "Team:Freiburg/Results/Own Device"

Figure 2: An illustration showing the exact setup of our device from a top perspective

As can be seen in Fig. 2, the basic setup is fairly simple. Light from an LED enters a lense where the light rays are made parallel. To achieve this, the distance from LED to the lense has to be exactly one focal length. The light then hits the iRIf slide, where it gets reflected (reflecting at the same angle it hit the slide) and enters a second lense, whose purpose is to project a sharp image of the slide onto the CCD chip of the camera.

To build your own iRIf device, we used the following parts:

Part	Description	Manufacturer / Partname
A fairly strong LED	In our case a 3W green 520nm LED	Cree XP-E on star circuit board
A cooling element	Used to prevent the LED from overheating	Fischer Elektronik ICK S
A constant-current-source	To ensure static LED light (no flickering)	Roschwege GmbH KSQ-3W
An AC/DC rectifier	Used to grant direct current to the LED	Goobay 67951
Two optical lenses	Here we used two identical 60mm lenses	Thorlabs AC254-060-A
A camera	We used a SLR camera	Canon 550D
A microfluidics chamber	Our chamber consists of an iRIf slide attached to a PDMS flow chamber	Made ourselves
Magnets	Used to attach the flow-cell to the device	5mm Neodymium magnets
A small syringe	We used a regular 10 ml syringe	BRAUN INJEKT 10ml
A microfluidic tube	Used to connect the flow chamber with the syringe	-
A case for the device	5 mm thick acrylic glass cutouts to hold the parts in place	Ordered at http://formulor.com

Figure 3 - A: The LED glued to the cooling element with thermal adhesive; B: The 10 magnets, each 5x5x5 mm as well as a PDMS flowcell (depth of the flowchamber: 30 µm); C: One of the lenses used in the setup

A major problem that we confronted when building the device from scratch was to assure that all components are at the exact distance and angle to each other. This is crucial as a slight misplacement of a component may lead to lower signal strengh, blurred images or in the worst case no signal at all. This can be difficult since our device doesn't rely on straight angles. We overcame this problem by designing a case for the device that ensures the right placement of the components in the device. This was archieved by calculating all the distances beforehand using simple physical law of optics. We realized this by drawing an exact vector graphic blueprint for our device. We then constructed a digital 3D model of the casing based on the vector blueprint, to avoid a costly and time-consuming trial and error process (Figure 2).

Figure 4: 3D model of our device, build from the vector files used to order the parts

Figure 5:The 3D model of our device without walls or top part. Parts have been colorized for clarification - Green: The wall where light exits the device and enters into the camera; Pink: a platform holding Cooling-Element+LED in place; Blue: platforms for holding the lenses in place; Gray: rear end wall where the flow chamber is attached to. The slits in the top and bottom part are where the magnets have to be fixed

We designed the casing so that all the necessary parts (lenses, LED) are held in the correct position safely during the measurement, but remain removable to grant easy transportation of the device (i.e. to the giant jamboree). Fig. 5 illustrates the parts that hold the lenses and LED in place.

After assuring that the 3D model of our device was set-up correctly, we created a vector graphic file which layed out all the parts needed for the casing in a 2D plain. Using this vector graphic file, we ordered the parts at Formulor, a service which lasers out parts from acrylic glass using a vector graphic as a template. The vector graphic template is shown in Figure 4, and may be downloaded and used by everyone to build their own device. To allow easy mounting of the casing we also provide an easy to understand manual. One advantage of using acrylic glass is that the parts can be glued together easily using a few drops of acetone, fusing the two parts together.

Figure 6: An image of the vector file used to order the parts. The vector file is used to laser out parts of a 5 mm acrylic glass board. Black lines are cut out by the laser, gray lines/areas are engravings. Refer to the download section to downloaded the vector graphic files.

The vector graphic file used to laser our the casing parts also contains a template for the parts which are necessary to attach the glass and PDMS slide to the device. These parts have to be lasered out of 1 mm thick acrylic glass (Figure 6). Once they are lasered out, the microfluidic tubes can be glued to the parts.

Figure 5 - left: a flow chamber consisting of an iRIf slide attached to a PDMS slide - center: a syringe attached to a pipett tip, used to inject antibodie solutions into the flow-chamber - right: the part of our device which connects the flow-chamber, the syringe and the iRIf device.

The most difficult part to build by oneself is the PDMS flow-chamber. For producing such flowchambers, a wafer has to be made in a cleanroom. The template used for our PDMS flow-cell is shown in Fig. 6. If your facility has an engineering department, there's a high chance that a cleanroom is present. Ask the personel in charge if they can help you out with producing your flow-cell. If you already use another type of microfluidic flow chambers, our device should still be compatible with it, though some adaptions might be necessary. If you have no possibility of creating a flow chamber, you might want to consider building a very simplified DIY flow-chambers from two glass slides, separeted by thin duct tape. Note that our device was not primarily build to support such a chamber though and would need appropriate modifications.

Figure 6: Layout used to produce the wafer of our PDMS flow chambers.

Figure 7: The device with and without the flowchamber mounted.

Download section

Click on the image to download a manual which will show you how to mount the casing of the device.

Legal notice

The iRIf detection method is patented. Biametrics and associated persons own patents concerning the detection principle. These patents are:

• Method for examining physical, chemical and biochemical interactions (DE102004051098.9, DE102005015030.6, EP05797776.1)


• Study of molecular interactions on and / or in thin layers (DE102007038797.2)


• Method and apparatus for determining reflection coefficients to filter arrangement with thin layers (DE102009019711.7)


• Again Detectable support for optical measuring methods (DE102009019476.2)