About Our Center
The Micro/Nanofluidics Lab at UofSC was established in 2007 and has more than 1,000 square feet of well-equipped research space.
The research taking place within the lab focuses on the following areas:
- nano/microfluidics, Lab-on-a-Chip,
- far-field optical nanoscopy and bioimaging,
- cancer detection and biomarker development,
- bioreactor and tissue engineering, and
- fluid dynamics, turbulence and mixing.
Area of Research
We developed an ultra-high temporal and spatial resolution velocimeter to measure flow velocity for transport phenomena in nano- and microfluidics. Whether a fluid flow has slip or non-slip boundary condition over a solid surface has been heavily debated over the past two centuries, but a convincing conclusion is still lacking. For conventional fluid dynamics, this seems not to be a big issue, and no-slip flow condition has been accepted for a long time, since the slip-length, if any, is very short compared with the thickness of the entire boundary layer. However, in microfluidics, especially in nanofluidics, the situation is quite different, where the slip length can be the same order or even longer than the entire channel’s transverse size, and non-slip flow condition has been challenged. With recent progress in microfluidics and nanofabrication, the field of nanofluidics is now gaining importance, since there are new areas of science that are important at the nanoscale and opportunity to develop novel functional devices. In nanofluidics, flow velocity field could have significant influence on the transport phenomena and performance (e.g. separation) in nanofluidic devices. However, there is currently no available method that can measure the flow velocity profile in nanochannels. On the other hand, transient electroosmostic flow (EOF) (e.g. sample injection) and AC electrokinetics have attracted many attentions in lab-on-a-chip. To optimize a device performance, high temporal resolution velocimeter is required to measure the fast dynamic process of the flow, such as the rise time of EOF. Current available velocimeter has limited temporal resolution much lower than the transient time scale in microfluidics.
Figure 1.1 Shows the Schematic of the nanoscopic velocimetry. (In the image gallery to the left of the page),
We developed a novel ultrafast far-field nanoscopic velocimeter based on laser induced fluorescence photobleaching (LIFPA) and stimulated emission depletion (STED) for application in nano- and microfluidics applications. For the first time we can measure the velocity profile in a nanocapillary of 360 nm inner diameter with spatial resolution higher than 70 nm. We also measured the EOF rise time in microcapillaries with a temporal resolution of about 5 microseconds, i.e. at least two orders higher than that of the state-of-the-art microPIV. This powerful new technology will provide us a new opportunity to validate theoretical model and explore new phenomenon and functionality in lab-on-a-chip.
Figure 1.2 Velocity profile of a nanocapillary of 360 nm inner diameter. The measurements were performed by moving the nanocube piezo stage in radial direction through the axis of the nanocaplillary. The whole width is divided into 18 steps for 5 runs. Each step is only 20 nm. The results are averaged with five events. The average velocity profile of the nanocapillary is attained.
Figure 1.3 The transient variation of fluorescence intensity in a capillary. It takes about 10 microseconds for the EOF to rise from 10% to 90% of its maximum steady state value at the measurement point. Figure 3 clearly shows the transient process with time step of 1 microsecond during the 10 microseconds period. Concerning the high frequency short noise with the period of about 4 microseconds, the temporal resolution in the current system is conservatively evaluated to be 5~10 microseconds.
1. Dielectrophoresis Separation of Colorectal Cancer Cells:
Separation of colorectal cancer cells from the other biological materials is important for clinical cancer diagnosis and cancer treatment. We use conventional dielectrophoresis (c-DEP) in a microfluidic chip to manipulate and isolate HCT116 colorectal cancer cells. As shown in Figure 2.1
2. A Dynamic Piezoelectric Micropumping Phenomenon:
A dynamic micropumping phenomenon has been observed, which is based on acoustic streaming generated by a piezotransducer actuated in d31 mode without check valve. As shown in Figure 2.2
Mixing, no matter laminar or turbulent, as widely exist in daily life, has great importance in science and industry. Our lab focused on high efficient laminar and turbulent mixing with low energy cost and space saving. Right now, experiment is the major research method we used. For future, simulations will follow up.
Figure 3.1. This is the wake flow at Re=3000(Re=UD/ν) without actuating. From the figure, the natural frequency of Kármán vortex street is about 7.8Hz.
Figure 3.2. This is the actuated flow at Re=3000. The actuating frequency is 7.8Hz which is the natural freuqncy of wake flow. The actuating intensity is 305.8% compared with mean flow. Clear vortex rolling up and stretching can be found in this figure. Although the spreading angle is limited, there is still some mixing at the downstream of the chamber.
Figure 3.3. This is the actuated flow at Re=3000. The actuating frequency is 5.3Hz. The actuating intensity is 305.8% too. Although the intensity is the same, much faster mixing can be achieved at this frequency.
The Nanoscopic Multimodality BioImaging Laboratory and The Micro/Nanofluidics Lab in USC pursuit research in nanoscopic and multimodality imaging of live cells, measurement and fabrication, and integration of the imaging technology with microfluidics for lab-on-a-chip applications.
Understanding subcellular structures, their functions and interaction between cells and their microenvironment is extremely important in biology, but our knowledge is limited. One of the reasons is that current optical microscopy, which has become an important tool in biological research, has limited resolution. In fact, all conventional optics-based measurements and imaging methods suffer from the diffraction limit in physics, and the spatial resolution is limited to roughly half wavelength of the light. Thus, conventional microscopes don’t have sufficiently spatial resolution to study structures and dynamic processes in biology. Furthermore, each type of microscope has limited function and performance. Visible light has limited penetration depth to image tissue and cell microenvironment. Each imaging technique has its own advantage and multimodality imaging allows acquisition of co-registered complementary data from samples and can provide more correlated data. Therefore, this project focuses on the development of (1) super resolution STED nanoscopy to bypass the diffraction limit to achieve high resolution, (2) multimodality bioimaging platform. STED nanoscopy has been an emerging breakthrough technology to overcome the diffraction limit to achieve nanoscale spatial resolution and won Nobel Prize in 2014. Multiphoton microscope can penetrate deep into tissues. Fluorescence lifetime imaging microscope (FLIM) can measure time-resolved dynamics.
We have not only an in-house developed, continuous wave (cw) laser based super resolution system, i.e. Stimulated Emission Depletion (STED), but also an in-house developed, cutting edge, two tunable femtosecond lasers based, far field, optical multifunctional and multimodality imaging system supported by NSF/MRI and NSF/CAREER. This ultrafast nanoscopic system integrates several technologies into a large system, which currently has the following performance:
- STED Nanoscopy
- Multiphoton (MP) microscopy
- Fluorescence life time imaging microscopy (FLIM) (TCSPC / FLIM, Becker & Hickl GmbH)
- Fluorescence resonant energy transfer (FRET)
- Second harmonic generation microscope (SHGM)
- Confocal microscope
- Laser induced fluorescence photobleaching anemometer (LIFPA)
- Integrated these functionalities with Lab-on-a-Chip for live cell imaging
The system consisted of a Coherent’s Chameleon Ultra II 80MHz (RoHS) Ti:Sapphire tunable femtosecond laser and Mira OPO – Fan Poled Ring Configuration optical parametric oscillator (OPO), a laser Scanning Confocal Microscope System, and PI’s PInano XYZ P-545.3C7 Piezo Stage with Capacitive Sensors with USB controller, TCSPC / FLIM, Becker & Hickl Inc, Ultra-low noise single photon detection module, etc. The system is for conventional bioimaging and bioimaging of live cells, flow velocity, concentration and temperature measurement, and nanofabrication.
Figure above shows the partial view of the USC in-house developed, cutting edge, two tunable femtosecond lasers based, far field, optical and multimodality nanoscopic system supported by MRI/ NSF
Transport Phenomena in Biomedical Systems
|BMEN 260||Intro to Biomechanics||3|
|BMEN 354||Transport in Biological Systems||3|
|EMCH 562 /BMEN 589||Biomicro/nanofluidics and Lab-on-a-Chip||3|
|EMCH 567 /BMEN 589||BioMEMS/NEMS||3|