Microcontact printing is a
versatile process to create micro- and nano-scale patterns using an elastomeric
stamp. The inventors have developed a method for local actuation and control of
elastomeric stamps which allows feedback control of stamp deformation for high
quality printing of sensitive stamp patterns.
This technology enables high quality pattern transfer, especially in roll-to-roll soft lithography or microcontact printing. Continuous stamps with precise dimensional control may be used to print nanowire grids in a robust manner for photovoltaic systems, to print electronics on flexible substrates in a high speed fashion for low cost sensors and displays, and to create nanoscale patterns which can greatly increase heat transfer rates and charge capture for power generation, energy storage and solar power technologies.
During microcontact printing, selective contact between the substrate and the micro- or nano-scale features on the stamp results in transfer of a molecular or fluid ink. Deformations in the soft elastomeric stamp - which can include sidewall collapse, roof collapse and buckling—occur at a critical collapse pressure. Thus, controlling the pressure on the stamp is imperative to avoiding undesired stamp deformation and obtaining a high quality pattern transfer.
The inventors use an electrostatic actuator (i.e. parallel plate capacitor) to modify the pressure distribution at the contact interface between elastomeric microcontact printing stamps and corresponding substrates. A gap is formed between two electrodes using patterned features in the elastomeric stamp. Conductive electrodes are placed against a rigid backing and the elastomeric stamp pattern. Energizing the electrodes will create an attractive force that causes the elastomeric features to deform much as they would at a printing interface. This will result in actuator behavior characterized by the actuator force and the stiffness of the stamp features.
Closed loop feedback control is achieved using electrostatic actuators for local stamp control and optical sensing to determine the feedback variable. This control variable can be used to calculate controller error, which determines the dynamic behavior of the controller and actuator signals. The independent local pressure zones can be used to control contact behavior, for example along the contact interface between a printing roller and impression roller.
Control and measure stamp pressure
distribution to avoid deformations
Smaller gap in parallel plate capacitor
and more sensitive actuator/sensor
New control paradigm allows for
multiple actuation methods to provide accuracy and dimensional stability