title: Multicolour micropatterning of thin films of dry gels.
abstract: Micropatterning of surfaces with several chemicals at different spatial locations usually requires multiple stamping and registration steps. Here, we describe an experimental method based on reaction-diffusion phenomena that allows for simultaneous micropatterning of a substrate with several coloured chemicals. In this method, called wet stamping (WETS), aqueous solutions of two or more inorganic salts are delivered onto a film of dry, ionically doped gelatin from an agarose stamp patterned in bas relief. Once in conformal contact, these salts diffuse into the gelatin, where they react to give deeply coloured precipitates. Separation of colours in the plane of the surface is the consequence of the differences in the diffusion coefficients, the solubility products, and the amounts of different salts delivered from the stamp, and is faithfully reproduced by a theoretical model based on a system of reaction-diffusion partial differential equations. The multicolour micropatterns are useful as non-binary optical elements, and could potentially form the basis of new applications in microseparations and in controlled delivery.
authors.affiliation: Department of Chemical Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208, USA.
authors.forename: Rafal
authors.initials: R
authors.lastname: Klajn
authors.forename: Marcin
authors.initials: M
authors.lastname: Fialkowski
authors.forename: Igor T
authors.initials: IT
authors.lastname: Bensemann
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Bitner
authors.forename: C J
authors.initials: CJ
authors.lastname: Campbell
authors.forename: Kyle
authors.initials: K
authors.lastname: Bishop
authors.forename: Stoyan
authors.initials: S
authors.lastname: Smoukov
authors.forename: Bartosz A
authors.initials: BA
authors.lastname: Grzybowski
mesh_terms: D002712:Chlorides; D003300:Copper / Q000737:chemistry; D003627:Data Interpretation, Statistical; D005290:Ferric Compounds / Q000737:chemistry; D005782:Gels / Q000737:chemistry*; D008420:Manufactured Materials; D012492:Salts / Q000737:chemistry*; D012685:Sepharose / Q000737:chemistry*
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D005782:Gels; D012492:Salts; D003300:Copper; D012685:Sepharose; C029892:cupric chloride; C024555:ferric chloride