Polymer-like Inorganic Double Helical van der Waals Semiconductor.

In high-performance flexible and stretchable electronic devices, conventional inorganic semiconductors made of rigid and brittle materials typically need to be configured into geometrically deformable formats and integrated with elastomeric substrates, which leads to challenges in scaling down device dimensions and complexities in device fabrication and integration. Here we report the extraordinary mechanical properties of the newly discovered inorganic double helical semiconductor tin indium phosphate. This spiral-shape double helical crystal shows the lowest Young's modulus (13.6 GPa) among all known stable inorganic materials. The large elastic (>27%) and plastic (>60%) bending strains are also observed and attributed to the easy slippage between neighboring double helices that are coupled through van der Waals interactions, leading to the high flexibility and deformability among known semiconducting materials. The results advance the fundamental understanding of the unique polymer-like mechanical properties and lay the foundation for their potential applications in flexible electronics and nanomechanics disciplines.

A new fabrication process for a microchip electrophoresis device integrated with a three-electrode electrochemical detector.

We report here a novel and simple process for the fabrication of a poly(methyl methacrylate) (PMMA)-based microchip electrophoresis device, integrated with a screen-printed three-electrode electrochemical detector that does not require a replicate mold. In this approach, a photoresist layer constitutes both an adhesion layer and side walls of 50 mum wide and 50 mum tall microfluidic channels on a screen-printed three-electrode PMMA substrate. Openings were drilled for buffer reservoirs on an additional piece of PMMA, then the final device was bonded in a PMMA/photoresist/PMMA sandwich configuration. This process is inexpensive, less time-consuming, and simpler compared with traditional fabrication methods. The combination of this PMMA-based microchip fabrication together with screen-printed electrode technology holds great promise for the mass production of a single-use micrototal analytical system. Successful determination of uric acid and L-ascorbic acid with the presented system validates its utility. In combination with a suitable electrochemical detector, this device holds much promise for the determination of other analytes in various biological samples for medical and clinical diagnosis.