Nano Groove and Prism-Structured Triboelectric Nanogenerators.

Enhancing the output power of triboelectric nanogenerators (TENGs) requires the creation of micro or nano-features on polymeric triboelectric surfaces to increase the TENGs' effective contact area and, therefore, output power. We deploy a novel bench-top fabrication method called dynamic Scanning Probe Lithography (d-SPL) to fabricate massive arrays of uniform 1 cm long and 2.5 µm wide nano-features comprising a 600 nm deep groove (NG) and a 600 nm high triangular prism (NTP). The method creates both features simultaneously in the polymeric surface, thereby doubling the structured surface area. Six thousand pairs of NGs and NTPs were patterned on a 6×5 cm2 PMMA substrate. It was then used as a mold to structure the surface of a 200 µm thick Polydimethylsiloxane (PDMS) layer. We show that the output power of the nano-structured TENG is significantly more than that of a TENG using flat PDMS films, at 12.2 mW compared to 2.2 mW, under the same operating conditions (a base acceleration amplitude of 0.8 g).

Control of Halogen Atom in Inorganic Metal-Halide Perovskites Enables Large Piezoelectricity for Electromechanical Energy Generation.

Regulating the strain of inorganic perovskites has emerged as a critical approach to control their electronic and optical properties. Here, an alternative strategy to further control the piezoelectric properties by substituting the halogen atom (I/Br) in the CsPbX3 perovskite (X = Cl, Br) structure is adopted. A series of piezoelectric materials with excellent piezoelectric coefficients (d33 ) are unveiled. Iodine-incorporated CsPbBr2 I demonstrates the record intrinsic piezoelectric response (d33 ≈47 pC N-1 ) among all inorganic metal halide perovskites. This leads to an excellent electrical output power of ≈ 0.375 mW (24.8 µW cm-2 N-1 ) in the piezoelectric energy generator (PEG) which is higher than those of the pristine/mixed perovskite references with CsPbX3 (X = I, Br, Cl). With its structural phase remaining unchanged, the strained CsPbBr2 I retains its superior piezoelectricity in both thin film and nanocrystal powder forms, further demonstrating its repeatability and versatility of applications. The origin of high piezoelectricity is found to be due to halogen-induced anisotropic lattice strain in the unit-cell along the c-axis, and octahedral distortion. This study reveals an avenue to design new piezoelectric materials by modifying their halide constituents and paves the way to design efficient PEGs for improved electromechanical energy conversion.

A precise and rapid early pregnancy test: Development of a novel and fully automated electrochemical point-of-care biosensor for human urine samples.

Human chorionic gonadotropin (hCG), a glycoprotein hormone secreted from the placenta, is an important biomarker for pregnancy. In this study, we designed a precise, rapid and fully automatic device with an electrochemical point-of-care biosensor capable of quantitative hCG detection from human urine samples for early pregnancy detection. Gold and Ag/AgCl electrodes, whose structure with optimum isopotential region and current density, were simulated using COMSOL Multiphysics® software and custom-made from Flex Medical. The sensing surface was fabricated with DSP self-assembled monolayers (SAMs) and covalently immobilized anti-hCG-beta antibody. The detection method involved a sandwich assay using anti-hCG alpha-HRP. Based on an automated agitation design implemented in our device, the surface reaction rate is significantly improved comparing to routinely performed sandwich assays, and therefore a rapid detection of very low concentration can be achieved. Electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) measurements were used to characterize the immobilization of the antibodies and to determine the sensor activities respectively. The sensors displayed a limit of detection (LOD) of 2.17 mIU/ml within established clinical hCG levels for early detection of pregnancy. They responded very well to hCG, but not to luteinizing hormone (LH), which has a high degree of cross-reactivity with hCG. The results showed that the immunosensor has high specificity, good reproducibility, and long-term stability for the detection of hCG in urine samples.

Long-Term Stability of Ferroelectret Energy Harvesters.

Cellular polypropylene (PP) has been recently used in energy harvesting applications. In this work, we investigate its viability and long-term stability under various operating conditions. Specifically, the effect of constant stress and stress cycling on output power and long-term stability of ferroelectret energy harvesters is analyzed. Our findings show that after 112 days constant stress significantly increases the piezoelectric charge constant d 33 and output power from 0.51 µW for a stress-free harvester to 2.71 µW. It also increases the harvester center frequency from 450 to 700 Hz and decreases its optimal resistance from 7 to 5.5 M Ω .