Magnetic lithography – A new method for chemical patterning of non flat surfaces. A new dimension in sequential detection and reactions in a microtube. Amos Bardea, Anand Tatikonda and Ron Naaman Department of Chemical Physics The Weizmann Institute of Science, Rehovot 76100, Israel
Method The new surface patterning method is called Magneto Lithography (ML). It is based on applying a magnetic field on the substrate using a permanent magnet and paramagnetic metal masks that define the spatial distribution and shape of the applied field. The second component in ML is ferromagnetic nanoparticles (Fe3O4) that are assembled onto the substrate according to the field induced by the mask. ML can be used either in a positive or negative approach. In the positive approach, the magnetic NPs react chemically with the substrate and are immobilized on selective locations, where the mask induces a magnetic field. In the negative approach, the magnetic NPs are inert to the substrate. Once they pattern the substrate, they block their site on the substrate from reacting with another reacting agent. After the adsorption of the reacting agent, the NPs are removed, resulting in a negatively patterned substrate. Patterning Gradient Properties from Sub‐ Micrometers to Millimeters by Magnetolithography
Positive Magnetolithography
(a)
SEM images of a positive ML pattern onto gold‐coated glass substrates, after they were functionalized with a self‐assembled monolayer
(b)
Scanning electron microscopy image of a pattern obtained on the surface of HD (a) and Co mask (b) with Fe3O4 nanoparticles. The particles are attracted to the region of maximum field gradient by the force exerted on domain walls
ML is patterning non planar surfaces: Inner tube patterning by enzyme using negative ML
Hydrophilic‐hydrophobic gradient on silicon surface. (a) Microscopic image of condensed water on the surface. Decrease in the droplet size from left to right indicates the increase in the hydrophobic nature of the surface. (b) Contact angle measurements of water droplets placed on the surface on which the hydrophobicity increases away from the center.
Sequential enzymatic reactions inside the tube obtained by patterning proteins on the inner surface of the tube
A scheme describing the multi‐peg magnet for applying ML in the tube.
The color of a pH indicator flushed in a solution with urea through a tube patterned with the enzyme urease. Biocatalyzed degradation of urea by urease alter the pH in the position of urease along the tube .
A scheme of sequential enzymatic reactions inside the tube obtained by patterning proteins glucose oxidase (GOx) and horseradish peroxidase (HRP) on the inner surface of the tube. GOx catalyzes oxidation of glucose by reduction H2O and produce gluconic acid with H2O2 . HRP catalyzes reduction of H2O2 and oxidation of TMB which precipitates on inner surface of the tube.
The precipitated oxidate TMB, resulting from the sequential reaction is seen as dark spots.
Reference a.) Bardea A. and Naaman R. Small, 5, 316-319 (2009). b.) Bardea A. and Naaman R. Langmuir 25, 5451-5454 (2009). c.) Bardea A., Bram A., Tatikonda A. K. and Naaman R. J. Am. Chem. Soc. 131, 18260-18262 (2009).
The change in pH along the tube, as obtained from the variation of the indicator’s color.
d) Tatikonda A. K., Bardea A., Shai Y., Yoffe A., and Naaman R. Nano Lett. 10, 2262-2267 (2010). e) Bardea, A. and Naaman, R., Magnetolithography. From the Bottom-Up Route to High Throughput. Advances in Imaging and Electron Physics, Vol. 164, 1-27, (2010).