We report direct observation of an unexpected anisotropic swelling of Si nanowires during lithiation against either a solid electrolyte with a lithium counter-electrode or a liquid electrolyte with a LiCoO(2) counter-electrode. Such anisotropic expansion is attributed to the interfacial processes of accommodating large volumetric strains at the lithiation reaction front that depend sensitively on the crystallographic orientation. This anisotropic swelling results in lithiated Si nanowires with a remarkable dumbbell-shaped cross section, which develops due to plastic flow and an ensuing necking instability that is induced by the tensile hoop stress buildup in the lithiated shell. The plasticity-driven morphological instabilities often lead to fracture in lithiated nanowires, now captured in video. These results provide important insight into the battery degradation mechanisms.

Using advanced in situ transmission electron microscopy, we show that the addition of a carbon coating combined with heavy doping leads to record-high charging rates in silicon nanowires. The carbon coating and phosphorus doping each resulted in a 2 to 3 orders of magnitude increase in electrical conductivity of the nanowires that, in turn, resulted in a 1 order of magnitude increase in charging rate. In addition, electrochemical solid-state amorphization (ESA) and inverse ESA were directly observed and characterized during a two-step phase transformation process during lithiation: crystalline silicon (Si) transforming to amorphous lithium-silicon (Li(x)Si) which transforms to crystalline Li(15)Si(4) (capacity 3579 mAh·g(-1)). The ultrafast charging rate is attributed to the nanoscale diffusion length and the improved electron and ion transport. These results provide important insight in how to use Si as a high energy density and high power density anode in lithium ion batteries for electrical vehicle and other electronic power source applications.

Nanoscale self‐folding of electron‐beam lithography patterned templates is used to create 3D devices for optics and biosensing.

From in situ transmission electron microscopy (TEM) observations, we present direct evidence of lithiumassisted welding between physically contacted silicon nanowires (SiNWs) induced by electrochemical lithiation and delithiation. This electrochemical weld between two SiNWs demonstrates facile transport of lithium ions and electrons across the interface. From our in situ observations, we estimate the shear strength of the welded region after delithiation to be approximately 200 MPa, indicating that a strong bond is formed at the junction of two SiNWs. This welding phenomenon could help address the issue of capacity fade in nanostructured silicon battery electrodes, which is typically caused by fracture and detachment of active materials from the current collector. The process could provide for more robust battery performance either through self-healing of fractured components that remain in contact or through the formation of a multiconnected network architecture.

The construction of three dimensional (3D) objects, with any desired surface patterns, is both critical to and easily achieved in macroscale, science and engineering. However, on the nanoscale, 3D fabrication is limited to particles with only very limited surface patterning. Here, we demonstrate a self-assembly strategy that harnesses the strengths of well established 2D nanoscale patterning techniques and additionally enables the construction of stable 3D polyhedral nanoparticles. As a proof of the concept, we self-assembled cubic particles with sizes as small as 100 nm and with specific and lithographically defined surface patterns.

It is well-known that one-dimensional nanostructures reduce pulverization of silicon (Si)-based anode materials during Li ion cycling because they allow lateral relaxation. However, even with improved designs, Si nanowire-based structures still exhibit limited cycling stability for extended numbers of cycles, with the specific capacity retention with cycling not showing significant improvements over commercial carbon-based anode materials. We have found that one important reason for the lack of long cycling stability can be the presence of milli- and microscale Si islands which typically form under nanowire arrays during their growth. Stress buildup in these Si island underlayers with cycling results in cracking, and the loss of specific capacity for Si nanowire anodes, due to progressive loss of contact with current collectors. We show that the formation of these parasitic Si islands for Si nanowires grown directly on metal current collectors can be avoided by growth through anodized aluminum oxide templates containing a high density of sub-100 nm nanopores. Using this template approach we demonstrate significantly enhanced cycling stability for Si nanowire-based lithium-ion battery anodes, with retentions of more than ~1000 mA·h/g discharge capacity over 1100 cycles.

We describe the use of conventional photolithography to construct three dimensional (3D) thin film scaffolds and direct the growth of fibroblasts into three distinct and anatomically relevant geometries: cylinders, spirals and bi-directionally folded sheets. The scaffolds were micropatterned as twodimensional sheets which then spontaneously assembled into specific geometries upon release from the underlying substrate. The viability of fibroblasts cultured on these self-assembling scaffolds was verified using fluorescence microscopy; cell morphology and spreading were studied using scanning electron microscopy. We demonstrate control over scaffold size, radius of curvature and folding pitch, thereby enabling an attractive approach for investigating the effects of these 3D geometric factors on cell behaviour.

We performed a large case-control study (3,932 cases, 15,562 controls) to investigate the association of hepatitis B virus (HBV) and hepatitis C virus (HCV) with hematopoietic malignancies in Korea, where HBV is endemic. HBV was present in 636 control patients (4.1%), 333 lymphoma patients (12.4%), and 75 leukemia patients (6.0%). HCV infection was present in 173 control patients (1.1%), 76 lymphoma patients (2.8%), and 18 leukemia patients (1.4%). Co-infection of HBV and HCV was present in one (0.007%) control patient, seven lymphoma patients (0.3%), and one leukemia patient (0.08%). HBV infection was associated with increased risks for most subtypes of B and T/NK-cell lymphomas, Hodgkin's lymphoma, and acute myeloid leukemia. HCV infection was associated with increased risks for diffuse large B cell lymphoma, extranodal marginal zone B cell lymphoma, peripheral T cell lymphoma, and acute lymphoid leukemia B cell early pre-B type. HBV seems to have a more important role than HCV in the pathogenesis of specific hematologic malignancies in Korea.