Magnetic Inks for Printing Functional Materials

Abstract

The demand for new novel materials has never been higher. This is driven by the advancement in technologies such as wearable electronics. As more novel applications emerge, the need for materials fit for the tasks follows. Many emerging fabrication techniques such as additive manufacturing strive to claim governance over new material properties. However, they remain largely subject to the use of homogeneous materials to create structures. Comparatively, natural structures, such as the cuticle arrangement in dragonfly wings dictate the functionality of the wing, lending one of the most efficient and manoeuvrable flyers on earth. Understanding that heterogeneities define function, we explore simple benchtop techniques to create readily functional materials. Such techniques involve the use of magnetic inks, which can be remotely manipulated using external magnetic fields. When miscible ferrofluid droplets are guided with a magnet through a viscous prepolymer, they trace trail patterns in their wake. It is shown that such patterns create pattern-specific reductions in the elastic modulus compared to the matrix. When the ink is comprised of magnetic carbon nanotubes, we show the simple dynamic-assembly of the ink into conductive networks. The networks are easily encased in a rubber like matrix to readily obtain functioning strain and oil sensors. In a similar manner biosensors are created using the immobilization of antibodies on the surface the nanotubes. The fabrication technique results in simple and economical sensors able to detect target biomarkers within sixty seconds. We equally explore how cells can be manipulated using engineered buffer solutions and magnetic field geometries, leading to simulations to optimize cell separation in microfluidic channels and macroscale patterning of blood and cancer cells. Magnetic inks can open an avenue to facile and economic fabrication techniques in all facets of industrial applications spanning from wearable electronics to biological sensors to tissue engineering.