The objective of this research line is the design and realization of handheld, battery-operated biochips based on surface-acoustic-wave (SAW) driven micropumps suitable for automated, high-throughput, cost-effective diagnostics. Our platform will couple the SAW-induced pumping mechanism (IIT patent T02007A000554) with original ultra-high sensitivity detection protocols that are being developed within IIT.
Original nanotopographies were developed to investigate cell-topography interaction. We designed and fabricated noisy nanothopographies with controlled directionality on biocompatible plastic substrates by thermal nanoimprint lithography. We demonstrated that the noise importantly affects cell spreading and focal adhesion maturation and spatial distribution, determining the cell phenotype obtained by the contact interaction with the nanomodified substrates. In case of neuronal cells, we also found that neurite path-finding is tolerant to topographical noise. This threshold can be modified by pharmacological stimuli acting on the cytoskeleton organization and cell contractility.
By exploiting nebulization anisotropy at crossing areas induced by laterally propagating SAWs, here we introduce basic fluidic unit operations that enable liquid loading and handling in 2D arrays of hydrophobic microchannels (Fig. 4). We demonstrate that, upon selectively activating single or multiple interdigital transducers (IDTs), fluids can be drawn from reservoirs (i.e.droplets at the channel entrances) into the chip micro-pipes and moved towards the desired positions of the channel grid. Motion direction and velocity are determined by the active IDT and by the SAW power, respectively. Splitting of the liquid flow can also be easily achieved by exploiting multiple SAWs propagating along different paths toward the selected split point. In this case, simultaneous filling of orthogonal microchannels is achieved. Hydrodynamics in microfluidic devices based on surface-acoustic-wave (SAW) driven acoustic-counterflow was studied for developing novel portable diagnostics systems. Particle-liquid suspensions were used as models to explore the suitability of the SAW technology for cell sorting and cell-liquid separation. Acoustic-counterflow can lead to a region nearby the liquid meniscus depleted from particles. The length of the depleted region was found to be particle-size dependent. By including fluorescent nanobeads in the liquids, flow lines were visualized during SAW-induced filling, showing the presence of vortexes and particle aggregation patterns due to acoustic-streaming and to the presence of parasitic standing SAWs. Functionalized nanoparticles were finally employed to explore the possibility of high-sensitivity on-chip detection protocols. From a technological point of view, efforts are being devoted to the engineering of a totally automated method to drive the liquids into the microchannels. To this end we devised a system of multiple SAW reflectors along the SAW delay lines. By applying a SAW with a frequency in resonance with an eigenmode of the resonator cavity, we demonstrated that water droplets pumped along the delay line automatically stop as they move into the cavity (IIT patent pending). This allows realizing complex, fully automated positioning of droplets or microchannel filling. This research activity is in collaborations with Dr. Lionetti, SSSA, Dr. Micera, SSSA e ETH, Dr. Pisignano, NNL, Dr. Ferrari, ETH e Dr. Spatz, Max Plank.
This combination will constitute a novel enabling technology for large-scale clinical screening with extreme resolution. Full portability and automation will make these devices suitable for point-of-care and even independent patient use. In a different configuration, these systems will also make it possible to carry out cell-level high-sensitivity molecular studies for drug and biological testing. One of the most limiting issues for the widespread use of lab-on-a-chip devices is the lack of compactness and portability of the diagnostic platforms. Indeed, the bare fluidic chip, which by itself is very compact, must be complemented with external control units, in most cases including pumps for liquid loading coupled with sample, ml-sized reagent reservoirs, and sensors to detect and control the movement of the reagents. Ideally, these pumps and all the control system should be miniaturized to allow integration at chip-level and eliminate the need for additional specialized or bulky equipment. Based on surface acoustic waves (SAWs), we recently introduced a novel class of fully integrated devices (Fig. 3), demonstrating fast and versatile liquid injection in hydrophobic, PDMS-based microchannels. We demonstrated that SAW-induced atomization within microchannels, followed by SAW-assisted coalescence, leads to very efficient liquid counterflow with respect to the SAW propagation direction (inverted drive).