Figure 3: An illustration showing the exact setup of our device from a top perspective.

As can be seen in figure 3, the basic setup is fairly simple. Light from an LED enters a lense to obtain a parallel light beam. To achieve this, the distance from the LED to the lense has to be exactly one focal length. The light hits the iRIf slide afterwards where it is reflected (in the same angle as it hits 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 rebuild our iRIf device, we used the following parts:

Part	Description	Manufacturer / Partname	Price[USD]
A fairly strong LED	In our case a 3W green 520 nm LED	Cree XP-E on star circuit board	10
A cooling element	Used to prevent the LED from overheating	Fischer Elektronik ICK S	9
A constant-current-source	To ensure static LED light (no flickering)	Roschwege GmbH KSQ-3W	15
An AC/DC rectifier	Used to grant direct current to the LED	Goobay 67951	16
Two optical lenses	Here we used two identical 60 mm lenses	Thorlabs AC254-060-A	160
A camera	We used a SLR camera	Canon 550D	200-400
A microfluidics chamber	Our chamber consists of an iRIf slide attached to a PDMS flowcell	Made ourselves
Magnets	Used to attach the flowcell to the device	5 mm Neodymium magnets	3
A small syringe	We used a regular 10 ml syringe	BRAUN INJEKT 10 ml	< 1
A microfluidic tube	Used to connect the flowchamber with the syringe	-	< 1
A case for the device	5 mm thick acrylic glass cutouts to hold the parts in place	Ordered at http://formulor.com	100

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 flowchamber (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 strength, blurred images or, in the worst case, no signal at all. This can be difficult since our device does not rely on straight angles. We overcame this problem by designing a case for the device that ensures the right placement of the components inside the device. This was achieved by calculating all the distances beforehand using physical laws 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 4).

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

Figure 5: The 3D model of our device without walls and top part. Parts have been colorized for clarification - Green: The wall where light exits the device and enters 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 flowchamber is attached to. The slits in the top and bottom part 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). Figure 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 6, 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 parts together. 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 cut from 1 mm thick acrylic glass. Once they are cut from the acrylic glass with a laser, the microfluidic tubes can be glued to the parts (figure 7). Once this is completed, these parts can be attached to the device with the magnets (figure 8)

Figure 6: An image of the vector file used to order the parts. The vector file is used to excise parts of a 5 mm acrylic glass board with a laser. 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 most difficult part to build by oneself is the PDMS flowchamber. For producing such flowchambers, a wafer has to be made in a cleanroom. The template used for our PDMS flowcell is shown in figure 9. If your facility has an engineering department, there is a high chance that a cleanroom is present. Ask the personel in charge if they can help you out with producing your flowcell. If you already use another type of microfluidic flowchambers, our device should still be compatible with it, though some adaptions might be necessary. If you have no possibility of creating a flowchamber, you might want to consider building a very simplified DIY flowchambers from two glass slides, separated by thin duct tape. Note that our device was not primarily build to support such a chamber though and would need appropriate modifications.

Figure 7 - left: a flow chamber consisting of an iRIf slide attached to a PDMS flowcell - center: a syringe attached to a pipette tip, used to inject antibody solutions into the flowchamber - right: the part of our device which connects the flowchamber, the syringe and the iRIf device.

Figure 8: The device with and without the mounted flowchamber.

Figure 9: Layout used to produce the wafer of our PDMS flowcell.

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)