Over the past two decades, contact transfer printing has evolved into a viable manufacturing technology that can deposit and pattern various organic, polymeric and inorganic ink materials with micro- and nano-scale precision. Contact printing relies on the elastomeric stamp that forms an adhesive and conformal contact with the ink layer during the ink pickup, and on the interfacial fracture of the ink-stamp interface during the ink transfer. Contact printing is inherently amenable to replicate large-area patterns on flat or curvilinear substrates, and it has potential to evolve into a universal platform for large-area, parallel deposition of multiple types of materials at the sub-micrometer length scale. However, the key to enabling such manufacturing is to establish clean and reliable methods for controlling interfacial adhesion and fracture mechanics during the ink pickup and release.
In the past, the speaker and his research group demonstrated that the adhesive stamp-ink interactions can be controlled by the chemical composition and stiffness of the polymeric stamps. For example, the surface energy of the polyurethane-acrylate (PUA) stamps can be controlled chemically, producing stamps with tunable polarity. As a consequence, high and low surface energy PUA stamps can be used to pattern a variety of electronic materials with ~100nm resolution and high uniformity.
Recently, the speaker and his research group have shown that modulation of the interfacial adhesion can be achieved with stamps made of shape-memory polymers that can change their contact area with inks using external stimuli. They have demonstrated that by modulating the stamp adhesion using thermo-mechanical cycles, several layers of inorganic and organic electronic materials can be picked up and deposited from the donor substrate to the receiver surface. Their approach permits patterning of multilayered stacks of organic/inorganic thin films with ~1µm resolution and high uniformity. They envision that the developed approach can be applied to pattern complete pixels of the µ-LED devices with sub-micrometer resolution using a unified set of materials and printing conditions.
About the speaker
Prof. Alexander A. Shestopalov received his PhD in Organic Chemistry from N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences in 2004 and PhD in Physical Chemistry from Duke University in 2009. He joined the University of Rochester in 2010 as an Assistant Professor, and he is now the Associate Professor of Chemical Engineering there.
Prof. Shestopalov’s research focuses on physical chemistry, synthetic organic chemistry, interfacial and colloidal science, interfacial thermodynamics, interfacial engineering and manufacturing at the micro- and nano-scales.
