title: Water-soluble sacrificial layers for surface micromachining.
abstract: This manuscript describes the use of water-soluble polymers for use as sacrificial layers in surface micromachining. Water-soluble polymers have two attractive characteristics for this application: 1) They can be deposited conveniently by spin-coating, and the solvent removed at a low temperature (95-150 degrees C), and 2) the resulting layer can be dissolved in water; no corrosive reagents or organic solvents are required. This technique is therefore compatible with a number of fragile materials, such as organic polymers, metal oxides and metals-materials that might be damaged during typical surface micromachining processes. The carboxylic acid groups of one polymer-poly(acrylic acid) (PAA)-can be transformed by reversible ion-exchange from water-soluble (Na+ counterion) to water-insoluble (Ca2+ counterion) forms. The use of PAA and dextran polymers as sacrificial materials is a useful technique for the fabrication of microstructures: Examples include metallic structures formed by the electrodeposition of nickel, and freestanding, polymeric structures formed by photolithography.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA.
authors.forename: Vincent
authors.initials: V
authors.lastname: Linder
authors.forename: Byron D
authors.initials: BD
authors.lastname: Gates
authors.forename: Declan
authors.initials: D
authors.lastname: Ryan
authors.forename: Babak A
authors.initials: BA
authors.lastname: Parviz
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002625:Chemistry, Organic / Q000379:methods; D003911:Dextrans / Q000737:chemistry; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods*; D007477:Ions; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods*; D009532:Nickel / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D003911:Dextrans; D007477:Ions; D010087:Oxides; D011108:Polymers; D012997:Solvents; D014867:Water; C006903:carbopol 940; D009532:Nickel; D002118:Calcium