Our research consists of characterizing the mechanical properties of environmental biofilms, using the Optical Coherence Elastography Technique. We aim to understand and predict how biofilm composition and structure corrugate to mechanical properties. Ultimately, this knowledge will be leveraged to enhance or eliminate different biofilms, depending on the application.
Okay, for the specific focus of characterizing the mechanical properties of biofilms, we have Cheriometry, we have Nanoindentation, Atomic Force Microscopy. We also have, you know, sort of new developmental techniques, for example, like you know, optical, you know, tweezers, magnetic tweezers, digital image correlation, and a host of others. Most of the previously used techniques either focus on overall mechanical property measurements, overlooking those, the Mesoscale, or highly-localized measurements that are not relevant at the Mesoscale.
And the Mesoscale is crucial, because that is the level that is relevant to physical attributes of biofilms. First, we've adapted the Optical Clearance Elastography Technique to characterize the mechanical properties of environmental biofilms. In this context, we've developed the methods, we've also developed inverse modeling tools to be able to deal with layered viscoelastic properties and also to analyze the complex microstructure of biofilms.
Our group is interested in quantifying the mechanical properties of biofilms from wastewater treatment plants. So, we're interested in learning what factors impact the stability and performance of biofilms. For example, does the stiffness of a biofilm impact the rate of sloughing?
To begin, gather the system components, including a Commercial Optical Coherence Tomography or OCT, a waveform generator, a transducer, a delay generator, a switch with BNC connections, BNC cables and adapters, optical posts and clamps. Connect the sync signal from the function generator to a switch. Then connect the other port of the switch to the delay generator.
Now, connect the output of the function generator to the transducer leads. Connect the outputs of the delay generator to the trigger channel at the back of the OCT base unit. Turn on the function generator, delay generator, OCT base unit, and the computer.
Then launch the OCT software. Position the transducer beneath the OCT lens. On the OCT software, select the Doppler Acquisition Mode and enable the External Trigger.
Place the commercially obtained granular biofilm under the lens in the sample holder. Using a translation stage, move the biofilms towards the tip of the transducer, ensuring the tip makes gentle contact with the sample surface. In the sample monitor window, click start and end points of the line of interest to specify the scan region.
Next, specify the number of pixels to 1, 523 along the scanning path and 1, 024 pixels along the depth of the sample. Increase the number of B scans to 50 to improve the signal-to-noise ratio of the Optical Coherence Elastography, or OCE images. Click the Scan button and turn on the switch.
Once the images appear on the screen, ensure that the Reference Intensity is within the optimum range. Then position the sample within the focal region of the OCT microscope objective. On the display toolbar, increase the higher value of the left hand side color bar and decrease the lower value of the right hand side color bar to adjust the Phase Contour in the OCE image.
To configure the function generator, press the Sign button to produce a single frequency sinusoidal voltage, starting from an excitation frequency of 4.6 kilohertz. Then set the voltage to an appropriate value and enable the output connector, by pressing the Output key. Next, click the Record button and acquire the OCT and OCE images.
Repeat the measurements at different frequencies to obtain cross-sectional images of the elastic wave field with different wavelengths.
