The objective of this Grant Opportunity for Academic Liaison with Indusrry (GOALI) Collaborative Research project is to to use magnetic nanowires to mimic the cilia found ubiquitously in nature in order to produce transformative in situ NEMS sensors of boundary layer flows and magnetically actuated mixers in microfluidic channels. In nature, tremendous variability is found in the geometries of cilia structures, as illustrated by the hair-like mechanoreceptor examples from fish, insects and mammals. Engineered cilia found in the literature exhibit cylindrical, curved and/or rectangular geometries. New fabrication methods that will not only improve control of these 2-D branching capabilities but will extend the ability to 3-D, allowing one to build in 3-D branching geometries in a wide variety of ferromagnetic materials. Fluid-structure interaction modeling will be used to predict optimal materials and geometries which will enable prototype hair-cell flow sensors and actuators to be fabricated. Nanowires geometries to date have been limited to planar structures and in our case cilia vertical to a planar substrate. The variety of shapes found in biological cilia suggests that optimization of nanowire geometries for use in flow sensors and actuators will require the ability to fabricate complex structures that are matched to targeted flow regimes. Therefore, novel templates will be used for 2D and 3D cilia geometries. For the microfluidic applications, tailoring of nanowire geometries requires understanding of low Reynolds number, laminar flows, i.e. regimes for which Navier-Stokes flow formulations for mean flows and Prandtl/Blasius solution formulations for the boundary layer are quite reasonable, and for which computational models of fluid-structure interaction compare well with measured flows. Computational modeling of 2D structures will be extended to the 3D structures grown in this investigation.
These cilia sensors and actuators will have impact well beyond the microfluidic applications that were proposed. Many micro- and nano-robotics would benefit from these nanosensors and arrays. Also, biological species themselves will be better understood with artificial sensing as their impact on the whole system can be evaluated without adverse affects to other functions as often occurs in biological studies. The PIs will organize a co-ed and girls-only summer camp in circuits and students from each school will be exposed to this interuniversity, interdisciplinary, industrially applied program.
This project researched a relatively young magnetostrictive alloy (FeGa) at the nanoscale, and incorporated nanowires of magnetic nanowires inside microfluidic channels to make a prototype nanoscale flow sensor. The intellectual merit of this proposal was based on studies of atypical electrochemistry, nanowire fabrication and characterization, and prototype microfludic flow sensor assemblies. First, a novel electrochemical technique was found that allowed repeatable growth of FeGa nanowires. This is significant because Ga is not easily electroplated from aqueous solutions as it tends to form oxidize and precipitate. A mechanism for the co-deposition of Fe and Ga was proposed and published. Second, the technique was used to fabrication FeGa nanowires which were characterized structurally, and magnetically. The latter provided insight to magnetic switching mechanisms at the nanoscale. Third, magnetic nanowires were integrated with microfluidic channels and the first ever nanowire flow sensors were tested. For broad impact, this project is leading to new nanoscopic sensors and actuators for more accessible health care, nanoreactors, underwater robotics and biology itself. We also had extensive outreach to disseminate the research to the public, including K12 summer camps, industrial talks, workshops for community college faculty, industry co-advised senior design projects, and several undergraduate researchers from other schools.
