Efforts to adapt and extend graphic arts printing techniques for demanding device applications in electronics, biotechnology and microelectromechanical systems have grown rapidly in recent years. Here, we describe the use of electrohydrodynamically induced fluid flows through fine microcapillary nozzles for jet printing of patterns and functional devices with submicrometre resolution. Key aspects of the physics of this approach, which has some features in common with related but comparatively low-resolution techniques for graphic arts, are revealed through direct high-speed imaging of the droplet formation processes. Printing of complex patterns of inks, ranging from insulating and conducting polymers, to solution suspensions of silicon nanoparticles and rods, to single-walled carbon nanotubes, using integrated computer-controlled printer systems illustrates some of the capabilities. High-resolution printed metal interconnects, electrodes and probing pads for representative circuit patterns and functional transistors with critical dimensions as small as 1 mum demonstrate potential applications in printed electronics.

Wearable contact lenses which can monitor physiological parameters have attracted substantial interests due to the capability of direct detection of biomarkers contained in body fluids. However, previously reported contact lens sensors can only monitor a single analyte at a time. Furthermore, such ocular contact lenses generally obstruct the field of vision of the subject. Here, we developed a multifunctional contact lens sensor that alleviates some of these limitations since it was developed on an actual ocular contact lens. It was also designed to monitor glucose within tears, as well as intraocular pressure using the resistance and capacitance of the electronic device. Furthermore, in-vivo and in-vitro tests using a live rabbit and bovine eyeball demonstrated its reliable operation. Our developed contact lens sensor can measure the glucose level in tear fluid and intraocular pressure simultaneously but yet independently based on different electrical responses.

Transparent electrodes that can remain electrically conductive and stable under large mechanical deformations are highly desirable for applications in flexible and wearable electronics. This paper describes a comprehensive study of the electrical, optical, and mechanical properties of hybrid nanostructures based on two-dimensional graphene and networks of one-dimensional metal nanowires, and their use as transparent and stretchable electrodes. Low sheet resistance (33 Ω/sq) with high transmittance (94% in visible range), robust stability against electric breakdown and oxidation, and superb flexibility (27% in bending strain) and stretchability (100% in tensile strain) are observed, and these multiple functionalities of the hybrid structures suggest a future promise for next generation electronics. The use of hybrid electrodes to fabricate oxide semiconductor transistors and single-pixel displays integrated on wearable soft contact lenses with in vivo tests are demonstrated.

Daniel Shir graduated with distinction and obtained a B.S. degree in materials science and engineering from the Pennsylvania State University in 2005. He is currently pursuing a Ph.D. degree in materials science and engineering at the University of Illinois at Urbana−Champaign under Professor John A. Rogers's guidance. Yun-Suk Nam obtained a Ph.D. degree in chemical engineering from Sogang University, Seoul, South Korea, in 2004. He is currently a postdoctoral researcher in the Department of Materials Science and Engineering at the University of Illinois at Urbana−Champaign. Seokwoo Jeon was born in Seoul, Korea, in 1975. He received his B.S. degree in 2000 and his master's degree with Professor Shinhoo Kang from Seoul National University in 2003 after one year as an exchange graduate student with Professor Paul V. Braun at the University of Illinois at Urbana−Champaign (UIUC). He is currently pursuing his Ph.D. degree in materials science and engineering at UIUC under the direction of Professor John A. Rogers. His research interests include soft lithography, 3D nanopatterning, microfluidic systems, and optically functional materials and devices. John A. Rogers obtained B.A. and B.S. degrees in chemistry and in physics from the University of Texas, Austin, in 1989. From MIT, he received S.M. degrees in physics and in chemistry in 1992 and the Ph.D. degree in physical chemistry in 1995.