A Versatile Approach for Biomaterial Patterning: Masked Ion Beam Lithography

  • PDF / 648,914 Bytes
  • 6 Pages / 612 x 792 pts (letter) Page_size
  • 81 Downloads / 242 Views

DOWNLOAD

REPORT


A Versatile Approach for Biomaterial Patterning: Masked Ion Beam Lithography Kenneth E. Gonsalves1*, Wei He2, David B. Poker3, Nikola Batina4, Lhadi Merhari5 1* Department of Chemistry & C.C. Cameron Applied Research Center, University of North Carolina, Charlotte, NC 28223, 2Institute of Material Science, U-136, University of Connecticut, Storrs, CT 06269, 3Oak Ridge National Laboratory, Oak Ridge, TN 37831, 4Departmento de Quimica, Universidad Autonoma Metropolitana-Iztapalapa, 09340 Mexico D.F., Mexico, 5 CERAMEC R&D, F-87000, Limoges, France ABSTRACT We describe a new approach for biomaterial patterning, viz, masked ion beam lithography. Poly (methyl methacrylate) (PMMA) film was used as a model system and subjected to Ca+ and P+ ion implantations through masks. Ca+ ion implantation was performed at an energy of 85 keV with a fluence of 1x1014 ions/cm2. P+ ion implantation was done at an energy of 85 keV with fluences of 1x1015 and 1x1016 ions/cm2. Arrays of holes were generated during these processes. AFM showed that the depth of the holes is in the nanoscale region. The surface hydrophobicity of the exposed PMMA films was investigated by contact angle measurement. The results indicated that ion implantation changed the surface hydrophobicity.

INTRODUCTION Microfabrication technology, widely used in the microelectronics industry, has recently been applied in micropatterning biological materials (“biopatterning”) [1]. Biopatterning has become increasingly important for the development of molecular and cellular biosensors, biomaterials, genomic and proteomic arrays [2]. In most cases photolithography is used. Although it is a quite mature technique, there are still some limitations in its application in biopatterning: (a) standard photolithography has multiple steps including film casting, exposure, developing and etching; (b) only the topography can be modified leaving a limited possibility to specifically tailor the surface chemistry of the patterns. In order to avoid the above shortcomings, we proposed to use ion implantation for the microfabrication process. Ion implantation is an important technique for implanting “dopants” in the manufacturing process of semiconductors. It is also a useful technique for improving surface properties of metals, such as wear and corrosion resistance [3]. In recent years, ion implantation has also been applied to modify polymer surfaces in order to improve tissue compatibility and blood compatibility [4]. The process is based on direct fabrication of patterns on polymers by ion irradiation. The fundamental underlying phenomena taken advantage of are the ion-polymer interactions. Indeed, compared to UV, X-ray or electrons, 1-400 keV ions lose a considerable amount of energy in the polymer leading to a thickness shrinkage of the exposed areas, thus inducing patterns of the desired shapes [5]. It is worth noting that no further treatment of the polymer is needed to reveal the features. The potential advantages of using ion implantation as a microfabrication techniques are: (a) si