AVS 50th International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeP

Paper BI-WeP1
Locally Addressable Electrochemical Patterning Technology (LAEPT) using Poly(L-lysine)-g-Poly(ethylene glycol), PLL-g-PEG

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: C.S Tang, Swiss Federal Laboratories for Materials Testing and Research, Switzerland
Correspondent: Click to Email

Protein-resistant polyelectrolyte, poly(L-lysine)-g-poly(ethylene glycol) PLL-g-PEG adsorbs spontaneously onto a substrate with surface contrast constituting of conductive titanium and non-conductive silicon-oxide. An applied potential between -0.4 and +1.7V removes the PLL-g-PEG from titanium but simultaneously, there was insignificant polyelectrolyte loss on the silicon-oxide. X-ray photoelectron spectroscopy confirmed the reduction of PLL-g-PEG on the titanium surface and it also indicated that approximately similar amount of PLL-g-PEG remained on the titanium oxide when low corresponding positive and negative voltages of up to 400mV were applied. At 1.7V, time-of-flight secondary ions mass spectroscopy and fluorescence microscopy distinctly demonstrated the intensity contrast between the retention of PLL-g-PEG on the silicon-oxide and PLL-PEG removal from titanium. It is believed that the native oxide layer of titanium undergoes morphological changes with ascending potential and this affects the adhesion stability of PLL-g-PEG on the titanium oxide surface. Electrochemical impedance spectroscopy monitored the voltage-induced changes in the oxide layer whose measured impedance and resistance were found to decrease dramatically with increasing voltage. Further investigations hinted that diffusional-controlled processes within the oxide caused complex morphological changes, eventuating in an unstable adhesion platform for weak PLL-g-PEG electrostatic binding. The difference in the response of an applied potential on the titanium/silicon region under electrochemical conditions permits the exploitation and regeneration of various immobilization techniques on titanium while maintaining a protein resistant background on the non-conductive region. This reliable method offers prospects in selective electrochemical patterning for the biomedical as well as semiconductor industries. It will be termed here as locally addressable electrochemical patterning technology, LAEPT.