Publications

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Pressure sensors that can both directly visualize and record applied pressure/stress are essential for e‐skin and medical/health monitoring. Here, using a WO 3 ‐film electrochromic device (ECD) array (10 × 10 pixels) and a ZnO‐nanowire‐matrix pressure sensor (ZPS), a pressure visualization and recording (PVR) system with a spatial resolution of 500 µm is developed. The distribution of external pressures can be recorded through the piezotronic effect from the ZPS and directly expressed by color changes in the ECD. Applying a local pressure can generate piezoelectric polarization charges at the two ends of the ZnO nanowires, which leads to the tuning of the current to be transported through the system and thus the color of the WO 3 film. The coloration and bleaching process in the ECD component show good cyclic stability, and over 85% of the color contrast is maintained after 300 cycles. In this PVR system, the applied pressure can be recorded without the assistance of a computer because of the color memory effect of the WO 3 material. Such systems are promising for applications in human‐electronic interfaces, military applications, and smart robots.

The integrated nanogenerator (NG) based on vertical nanowire (NW) arrays is one of the dominant designs developed to harvest mechanical energy using piezoelectric nanostructures. Finite element method (FEM) simulations of such a NG are developed using ZnO NWs in compression mode to evaluate its performances in term of piezoelectric potential generated, capacitance, induced mechanical energy, output electrical energy, and efficiency. This evaluation is essential to correctly understand NG operation. Three main issues are highlighted. The mechanical and electrical structures of the NG as an integrated system are optimized, and strategies for concentrating the mechanical strain field in the NWs and increasing the force sensitivity are developed. In addition, the influence of NWs length and diameter on NG performances is investigated. The optimization results in a piezoelectric nano composite material where global performances are improved by mean of long and thin NWs.

Hybrid power testing platform system for fuel cell city bus was comprised of fuel cell,power battery(lead-acid battery),DC/DC inverter,traction motor,and dynamometer etc.Through the control strategy researching and the platform system integration,hybrid power testing platform achieved load leveling and simulated the driving cycles of city bus.

Abstract Triboelectric nanogenerator (TENG) harvesting ocean wave energy is an effective method to alleviate the energy crisis. However, the breakdown phenomenon is ubiquitous for the TENG with a large area of dielectric layer, which not only limits the output and reliability but also highly risks the device failure. Here, a self‐recovery TENG (SR‐TENG) featuring high breakdown resistance is designed, which achieves a high output charge density of 4.24 mC m −2 with the assistance of the charge excitation technique, as well as maintains 87% of the initial output even after six times fierce electric breakdown, minimizing the negative impacts of the breakdown phenomenon. Besides, based on the SR‐TENG, a symmetric anaconda‐shaped self‐charge excited TENG is designed for effective water wave energy harvesting. This work not only sheds light on the self‐recovery phenomenon in TENGs, but also represents a significant step toward the high performance TENG featuring high breakdown resistance and ultimate stability, accelerating the practical applications of TENG for blue energy harvesting.

Flexible sensors are highly desirable for tactile sensing and wearable devices. Previous researches of smart elements have focused on flexible pressure or temperature sensors. However, realizing material identification remains a challenge. Here, we report a multifunctional sensor composed of hydrophobic films and graphene/polydimethylsiloxane sponges. By engineering and optimizing sponges, the fabricated sensor exhibits a high-pressure sensitivity of >15.22 per kilopascal, a fast response time of <74 millisecond, and a high stability over >3000 cycles. In the case of temperature stimulus, the sensor exhibits a temperature-sensing resolution of 1 kelvin via the thermoelectric effect. The sensor can generate output voltage signals after physical contact with different flat materials based on contact-induced electrification. The corresponding signals can be, in turn, used to infer material properties. This multifunctional sensor is excellent in its low cost and material identification, which provides a design concept for meeting the challenges in functional electronics.

A method for the large-scale fabrication of patterned organic nanowire (NW) arrays is demonstrated by the use of laser interference patterning (LIP) in conjunction with inductively coupled plasma (ICP) etching. The NW arrays can be fabricated after a short ICP etching of periodic patterns produced through LIP. Arrays of NWs have been fabricated in UV-absorbent polymers, such as PET (polyethylene terephthalate) and Dura film (76% polyethylene and 24% polycarbonate), through laser interference photon ablation and in UV transparent polymers such as PVA (polyvinyl acetate) and PP (polypropylene) through laser interference lithography of a thin layer of photoresist coated atop the polymer surface. The dependence of the structure and morphology of NWs as a function of initial pattern created by LIP and the laser energy dose in LIP is discussed. The absence of residual photoresist atop the NWs in UV-transparent polymers is confirmed through Raman spectroscopy.

Understanding of the molecular processes that led to the first biomolecules on Earth is one of the key aspects of origins-of-life research. Depsipeptides, or polymers with mixed amide and ester backbones, have been proposed as plausible prebiotic precursors for peptide formation. Chemical characterization of depsipeptides in complex prebiotic-like mixtures should benefit from more efficient ion sources and ultrahigh-resolution mass spectrometry (UHR-MS) for elemental composition elucidation.A sliding freestanding (SF) Triboelectric Nanogenerator (TENG) was coupled to glass nanoelectrospray emitters for the analysis of a depsipeptide library created using 11 amino acids and 3 alpha-hydroxy acids subjected to environmentally driven polymerization. The TENG nanoelectrospray ionization (nanoESI) source was coupled to an UHR Orbitrap mass spectrometer operated at 1,000,000 resolution for detecting depsipeptides and oligoesters in such libraries. Tandem mass spectrometry (MS/MS) experiments were performed on an Orbitrap Q-Exactive mass spectrometer.Our previous proteomics-like approach to depsipeptide library characterization showed the enormous complexity of these dynamic combinatorial systems. Here, direct infusion UHR-MS along with de novo sequencing enabled the identification of 524 sequences corresponding to 320 different depsipeptide compositions. Van Krevelen and mass defect diagrams enabled better visualization of the chemical diversity in these synthetic libraries.TENG nanoESI coupled to UHR-MS is a powerful method for depsipeptide library characterization in an origins-of-life context.