Unique wrinkling behavior of stiff thin films on shape memory polymers

Shape memory polymers (SMPs) can remember two or more distinct shapes, and therefore can have many applications. We here presents combined experimental and theoretical studies on the wrinkling of stiff thin films on SMPs. Experimental results show well-defined, wavy profiles of the thin films. Time and temperature dependent wrinkle formation and evolution were observed. It was shown that both wrinkling wavelength and amplitude increase with SMP relaxation. This is different from earlier observations of thin film wrinkling on soft substrates, which show decreasing wavelength and increasing amplitude when compression increases. Finite element simulations accounting for the thermomechanical behavior of SMPs were used to study wrinkling of thin films on SMPs, which show good agreement with experiments. This study can have important implications in surface engineering, stretchable electronics, and advanced manufacturing

Electronic eyes enabled by stretchable electronics: mechanics, materials, and optics

Stretchable electronics combines the electronic performance of conventional wafer-based semiconductor devices and mechanical properties of a rubber band, and thus can have very broad applications that are impossible for hard, planar integrated circuits that exist today. Examples range from surgical and diagnostic implements that integrate with the human body to provide advanced therapeutic capabilities, to structural health monitors and inspection systems for civil engineering. In this discussion, I will discuss our development of electronic eye-ball cameras enabled by stretchable electronics and mechanics. Electronic eye-ball cameras have high performance photodetectors distributed on curvilinear surfaces and offer advantages over comparable systems that use conventional, flat detector arrays. Our recently developed artificial compound eye with designs inspired by arthropod eyes will also be introduced. This artificial compound eye can achieve wide-angle field of view, low aberrations, high acuity to motion and an infinite depth of field, which were not possible through conventional technology. Mechanics, materials, and optics of these systems will be discussed

Elasto-plastic Analysis of High-strength Concrete Shear Wall with Boundary Columns Using Fiber Model

In this study, an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load. The boundary column and shear wall were divided into fiber elements, and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens. The results show that the finite element analysis results were in good agreement with the experimental results. The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall. The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters: axis compression ratio, height to width ratio, ratio of vertical reinforcement, and ratio of longitudinal reinforcement in the boundary column. The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease. The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase. The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility. The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase

Metal oxide semiconductor nanomembrane-based soft unnoticeable multifunctional electronics for wearable human-machine interfaces

Wearable human-machine interfaces (HMIs) are an important class of devices that enable human and machine interaction and teaming. Recent advances in electronics, materials, and mechanical designs have offered avenues toward wearable HMI devices. However, existing wearable HMI devices are uncomfortable to use and restrict the human body's motion, show slow response times, or are challenging to realize with multiple functions. Here, we report sol-gel-on-polymer-processed indium zinc oxide semiconductor nanomembrane-based ultrathin stretchable electronics with advantages of multifunctionality, simple manufacturing, imperceptible wearing, and robust interfacing. Multifunctional wearable HMI devices range from resistive random-access memory for data storage to field-effect transistors for interfacing and switching circuits, to various sensors for health and body motion sensing, and to microheaters for temperature delivery. The HMI devices can be not only seamlessly worn by humans but also implemented as prosthetic skin for robotics, which offer intelligent feedback, resulting in a closed-loop HMI system

An Improved Transplantation Strategy for Mouse Mesenchymal Stem Cells in an Acute Myocardial Infarction Model

To develop an effective therapeutic strategy for cardiac regeneration using bone marrow mesenchymal stem cells (BM-MSCs), the primary mouse BM-MSCs (1st BM-MSCs) and 5th passage BM-MSCs from β-galactosidase transgenic mice were respectively intramyocardially transplanted into the acute myocardial infarction (AMI) model of wild type mice. At the 6th week, animals/tissues from the 1st BM-MSCs group, the 5th passage BM-MSCs group, control group were examined. Our results revealed that, compared to the 5th passage BM-MSCs, the 1st BM-MSCs had better therapeutic effects in the mouse MI model. The 1st BM-MSCs maintained greater differentiation potentials towards cardiomocytes or vascular endothelial cells in vitro. This is indicated by higher expressions of cardiomyocyte and vascular endothelial cell mature markers in vitro. Furthermore, we identified that 24 proteins were down-regulated and 3 proteins were up-regulated in the 5th BM-MSCs in comparison to the 1st BM-MSCs, using mass spectrometry following two-dimensional electrophoresis. Our data suggest that transplantation of the 1st BM-MSCs may be an effective therapeutic strategy for cardiac tissue regeneration following AMI, and altered protein expression profiles between the 1st BM-MSCs and 5th passage BM-MSCs may account for the difference in their maintenance of stemness and their therapeutic effects following AMI