Research

Acoustofluidics, handling of particles and fluid interfaces using ultrasonic waves has emerged as a power tool in the recent past due to its inherent nature of gentle, precise and contactless manipulation. Two types of waves, namely bulk and surface acoustic waves can be employed to perform manipulations. Bulk acoustic waves (BAW) can be generated using piezoelectric transducers. Bulk acoustic standing waves can be produced in a channel by adjusting the frequency of the wave with respect to the channel dimensions. Surface Acoustic waves (SAW) can be generated using an array of interdigitated electrodes patterned on a piezoelectric substrate. Both travelling surface acoustic waves (TSAW) and standing surface acoustic waves (SSAW) can be employed for the manipulation of particles and fluid interfaces.

In our group, we have been working towards uncovering the physics of intricate coupling between sound waves and interfaces (both particles and liquid interfaces) leading to fascinating phenomena. We have been also trying to exploit the new understanding for developing new microfluidic processes and devices.

Magnetofluidics, manipulation of particles and fluid interfaces using magnetic field, has emerged as a powerful tool in the recent past due to its inherent nature of contactless actuation, low energy requirement and biocompatibility . The technique is versatile and enables the manipulation of both magnetic (ferromagnetic) as well as non -magnetic (diamagnetic) objects . Depending upon the nature of the objects to be manipulated, the technique can be classified into positive and negative magnetofluidics . When the magnetic susceptibility of the medium is less than that of object, the motion of the object is toward the maximum magnetic field and the technique is known as positive magnetofluidics . Similarly, when the magnetic susceptibility of the medium is more than that of object, the motion of the object is toward the minimum magnetic field and the technique is termed as negative magnetofluidics .

In our group, we have been trying to unravel the physics of intricate coupling between magnetic field and interfaces (both ferromagnetic and diamagnetic particles and liquids) leading to interesting observations . We have been also trying to utilize the new understanding for developing new microfluidic processes and devices .

Capillary and wetting phenomena are important on small scales that always imply large surface-to-volume ratios: the smaller the system, the larger the fraction of atoms or molecules are located at interfaces – the fundamental reason why interfacial effects are crucial in all branches of micro- and nanotechnology. Wetting is the ability of a liquid to maintain contact with a solid or another liquid surface, resulting from intermolecular interactions when the two are brought together. Capillarity is the ability of a liquid to flow in narrow spaces without the assistance of or even in opposition to external forces like gravity. It occurs because of intermolecular forces between the liquid and surrounding solid surfaces. If the flow length scale is sufficiently small, then the combination of surface tension and adhesive forces between the liquid and wall act to propel the liquid.

In our group, we have been working towards discovering novel wetting and capillarity phenomena and unraveling the fundamental mechanism responsible. We are also committed toward utilizing the understanding to develop processes and devices for different applications.

Early detection of systemic inflammatory response syndrome (SIRS) helps in managing sepsis and minimizing its adverse effects in patients. Gaseous signaling molecules, also referred to as gasotransmitters, play a vital role in the process of inflammation. The concentration of these compounds gives crucial information about the state of inflammation. Thus, the change in the level of such gasotransmitters in patients’ blood is a prognostic marker of sepsis. We have developed a microfluidic device that utilizes fluorimetry for the continuous monitoring of the concentration of different gasotransmitters such as H2S, H2O2 , NO and CO in patients’ blood. We have also integrated the optofluidic detection device with a microfluidic plasma separation unit for on-chip blood cell separation and sepsis detection for use in clinical settings.

Circulating tumor cells (CTCs) occur in very low frequency in whole blood, i.e. 1 mL human blood could contain 1-100 CTCs among few million white blood cells (WBCs) and a billion red blood cells (RBCs). Quantification of CTCs have high clinical value as these cells usually indicate tumor metastasis and facilitate real-time monitoring of systemic therapy by sequential peripheral blood sampling. Molecular characterization of CTCs helps to understand the mechanism of metastasis, enables identifying therapeutic targets and contributes to personalized, anti-metastatic therapies.

Early diagnosis of dengue biomarkers by employing a technology that is less labor- and time-intensive and offers higher sensitivity and lower limits of detection would find great significance in the developing world. We have been developing a biosensor that exploits the localized surface plasmon resonance (LSPR) effect of nanostructures to detect dengue NS1 antigen, which appears as early as the onset of infection. The biosensor integrates a blood-plasma separation to develop lab-on-chip device that facilitates rapid diagnosis (within 30 min) of dengue NS1 antigen from a small volume of whole blood. From 10 µL of whole blood spiked with NS1 antigen, our biosensor reliably detects 0.06 µg/mL of NS1, which lies within the clinical limit observed during the first seven days of infection, with a sensitivity of 9 nm/(µg/mL). These results confirm that the proposed LSPR biosensor can potentially be used in point-of-care dengue diagnostics.