Self-assembled monolayers (SAMs) form when organic molecules are chemisorbed on solid surfaces. Such SAMs are an important tool to synthesize surfaces with defined molecular and macroscopic properties. In this way, active surfaces in Micro-Electro-Mechanical Systems (MEMS) and microfluid systems can be prepared by coupling of active ligand groups (X in the figure below), with e.g. chemical, physical or biological functions, to surfaces functionalized by SAM molecules.
A surface can be functionalized to induce either a chemical, biological or physical function by self assembled monolayers. Typically a long alkylchain is anchored to the substrate using groups that chemically bond to the substrate. To this chain an active ligand, that will control the surface properties, can be attached.
Example of surface modification with molecules to obtain a very hydrophobic surface
Surface wettability and adhesive properties
These devices are again important in business areas such as:
Patterning of self assembled monolayers
A key to utilize and increase the design degree of freedom in many advanced applications involving SAMs, such as biosensors, microfluidic systems and microelectronic circuitry fabrication, is the ability to spatially modulate the surface reactivity of the pendant X groups of the chemisorbed film. On some surfaces such patterning can be performed using lithographic methods involving high energy radiation such as UVC light. Another solution is to mechanically “stamp” the molecules on the surface in an already predefined pattern (microcontact printing).
Water vapour reveals a pattern on a gold coated surface due to differences in wettability. The pattern was generated using photo-oxidation of the SAM layer using a mask and UVC-light.
Water vapour reveals a pattern on a silicon surface due to differences in wettability. The pattern was generated using microcontact printing where patterned silicone stamp is saturated with molecules which then are “stamped” on the silicon surface.
Contact person: Frode Tyholdt
