Micro-Nano-Technology (MNT)
Research Activities
- Develop and characterize the performance of a 5-channel device for formulation of liposome nanovials and determine the optimal conditions to minimize free dye in solution. Previously we demonstrated liposome formation using hydro-dynamic focusing in a microfluidic network which enables us to produce liposomes of a controlled size and size distribution in a reproducible fashion. Liposomes were characterized with batch dynamic light scattering (DLS) and multi angle laser light scattering (MALLS) of unfractionated samples. However, this measurement only provides ensemble averages. In the past year, we have implemented a more detailed and accurate measurement technique that allows for precise characterization of liposome populations using asymmetric flow field flow fractionation (AFFFF) before MALLS and DLS. Details about liposome size and size distribution allow further elucidation about the liposome self-assembly process.
- Develop methods and optimize formulation conditions for vesicle-templated alginate nanoparticles. Biology is rife with the motif of molecules self-assembling into larger functional elements. In fact, a human being can be thought of as the product of the directed self-assembly of cells into a functional person. We have taken a simple biologically inspired system, the liposome, and used it to template the self-assembly of biomolecules into nanoparticles of controlled size and architecture. We have demonstrated that liposomes can be used to template the gelling of alginate into nanoparticles that have a size equivalent to that of the parent liposome. This allows for the control of the nanoparticle size through modulation of the templating liposome’s size. In contrast to liposomes and other vesicles, these nanoparticles appear to be extremely stable to temperature variations, detergent treatment, and changes in buffer osmolarity and pH.
- Design, fabricate, and test a prototype device for accurate pH measurements in a micro-fluidic network. Lab-on-a-Chip (LOC) systems might enjoy more widespread use if reliable and accurate electronic chemical sensors are more closely integrated with the microfluidic networks. In this work, an ion-sensitive field-effect transistor (ISFET) and an Ag/AgCl quasi-reference electrode were integrated with a polymeric surface-mounted microfluidic network in order to demonstrate electrochemical measurement of pH in the planar microfluidic format. The gate insulator of the n-type ISFET was an SiO2 / Si3N4 stack (85 nm / 38 nm). The device was observed to be temperature sensitive, and several time-varying electronic characteristics were explained in terms of resistive heating of the FET channel. The drain current (ID), drain voltage (VDS) transfer characteristics were recorded, and the drain-to-source impedance was measured while the device was exposed to flowing aqueous solutions. Transfer characteristics from VDS = 0 V to 3 V indicated that the device functioned as a depletion-type FET. At steady-state, the drain-to-reference voltage (VDR) gave linear calibrations for flowing buffer solutions from pH 3 to pH 11 of approximately 63 mV pH-1. The ISFET was shown to be a viable all-electronic pH sensor for planar microfluidics. With additional characterization, the device may lead to improved pH measurement traceability for portable LOC systems.
- Fabricate and characterize covalently bound polyelectrolyte multilayers. Evaluate their poten-tial as a nanogel for trapping or separating biomolecules (proteins, DNA, etc.). A unique method for layer-by-layer patterning and crosslinking of polymers with dissimilar cell attachment characteristics is presented. Polyelectrolyte multilayers (PEMs) were deposited and exposed with UV light through a binary photomask to form a patterned upper stratum where cells are not viable and a lower cytophilic stratum. This work describes the facile synthetic procedures used to make crosslinkable polyelectrolytes, demonstrates photopolymerization of the functionalized polyelectrolytes, and reveals the cytophobic character of the new synthesized polyelectrolytes for future cell culture applications.
- MIG anniversary report, “Standardization and the Study of the
- Identify and develop MEMS “Living Stan-dards” with SEMI. The MNT Project is currently championing MNT standardization efforts in two venues: ASTM and SEMI. Highlighting the need for MNT standardization is the number of companies and other organizations participating in these standards activities. The first four MNT standards (on in-plane lengths, residual strain, strain gradient, and terminology) originated in the ASTM E08.05.03 Task Group on Structural Films for MEMS and Electronic Applications. Also within this task group, standards for determining Young’s modulus, ultimate strength, and fatigue for a surface micromachining process are being developed at
- Complete development of a prototype micro-fluidic forensic DNA separation system for dem-onstration to forensic scientists. The goal of this effort was to develop a plastic microfluidic-based system for high-speed electrophoretic analysis of DNA fragments for forensic applications. The development of this device has been completed, and we have approached several companies in the DNA analysis community to present this technology for future commercial development. We have formalized a Collaborative Research and Development Agreement (CRADA) with Network Biosystems, Inc., and are currently working with them to transfer this technology to a commercially available product, thus expediting the availability of this instrumentation to the forensics community.
- Develop an integrated microwave transmis-sion line with a microfluidic network and investi-gate the feasibility of using microwave power to heat fluid in specific points in the channel. Rapid thermocycling and localized and selective heating of fluids on-chip is important for micro total analysis system (microTAS) applications. We have developed a new approach to accomplish this by microwave dielectric heating using an integrated microwave transmission line to deliver heat to a specific region in a microfluidic network. An elastomeric microfluidic channel was positioned over a coplanar waveguide (CPW) that was fabricated on a glass substrate. S-parameter and temperature measurements of the device were used with a theoretical analysis to fully characterize the temperature rise of the fluid by microwave power absorption. In this unoptimized exploratory device, a 0.95 °C per mW temperature rise was observed at 15 GHz. Our theoretical analysis confirms that classical mi-crowave absorption theory is valid at this scale.
- Investigate the feasibility of using microwave power to lyse cells in a microfluidic device. Cell lysis is a method used to disrupt the cell membrane and release the intracellular components such as proteins, DNA, and RNA, among others. Chemical, mechanical, and thermal lysis methods are used to lyse cells conventionally. The technique of choice will be dictated by the cell origin, the difficulty in cell membrane and/or wall disruption, and its compatibility with the bio-molecules or organelles to be recovered or extracted in the subsequent steps. Thermal lysis is the method (among the above mentioned methods) that is compatible only with nucleic acids analysis, since the high temperature attained will denature the cell proteins, and the organelles will likely be disrupted. We have successfully demonstrated the application of microwave power to lyse cells in a microfluidic device. Microwave heating presents a technique to heat aqueous solutions in a very rapid way since the media is heated directly and heat does not need to be conducted through the walls of the container to the media. Integrating microwave guides in a microfluidic system should allow for the rapid lysing of cells and quick transport of the cell components to clean up, PCR, and separation steps that are necessary down the road in a micro total analysis system.
