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In this work, we refer to the fraction of hydrides and vinyl groups consumed in cross‐linking reaction as a variation of the properties of poly(dimethylsiloxane) (PDMS) with varying the formulation of a curing agent from 3.2 wt % to 50 wt %. Young's modulus, density, and refractive indices of PDMS were observed to have a maxima at a formulation of about 10 wt % of cross linker. The intensity of the Raman band for the SiH stretching mode in cross‐linker is almost zero if the cross‐linking agent is less than 10 wt %, but it is linearly increasing with increasing the content of cross‐linker. The dependence of the elastic modulus on the formulation could be explained in terms of the fraction of cross‐linked network. The analytical framework proposed in this work could be used for optimizing the formulation of PDMS and hence its properties can be tailored for specific applications. In this work, we have propose a framework to correlate the dependence of the properties of PDMS on its formulation with the fraction of SiH as well as CC bond, which consumed by cross‐linking reaction. The effect of the formulation on the mechanical, physical, optical, and wetting properties was investigated by measuring the Young's modulus, density, refractive index, and contact angle of the resultant solid PDMS substrate. These properties showed extrema at the formulation of around 10 wt % curing agent. We have further tried to study the content of SiH and CC groups in quantitatively by utilizing Raman spectroscopy and UV absorption spectrophotometry, respectively. We successfully explained the dependence of the above properties of the PDMS on the formulation in terms of the fraction of the cross‐linked network. Finally, we confidently propose that the analytical framework developed in this work can be useful to predict a formulation to optimize the properties of PDMS for future applications in the biomedical and industrial fields.

Among the many types of wasted energy around us, mechanical energy has been considered to have a considerable amount of potential to be scavenged due to its abundance and ubiquity in our lives. To convert ambient mechanical energy into electrical energy efficiently, the triboelectric nanogenerator (TENG) has been intensively studied. Polydimethylsiloxane (PDMS), due to its superior mechanical and electrical properties, has commonly been selected as a friction layer in TENGs. Herein, it is newly discovered that the output power of a fabricated TENG is highly correlated with the Young's modulus of PDMS. An enhancement of the output power is achieved by the optimization of the PDMS mixture ratio. In addition, to improve the output power of the TENG further, a well-ordered microstructure was directly created on the surface of the PDMS by means of ultrafast laser irradiation. Direct patterning to create the surface morphology on the PDMS surface with the aid of laser irradiation is more efficient than conventional surface modification techniques such as replication and a few microfabrication steps. Compared to a control TENG using bare PDMS, an increase in the output power of more than twofold is achieved by an experimental TENG using patterned PDMS with a laser power of 29mW. The TENG utilizing the patterned PDMS achieves a maximum output power density level of 107.3μW/cm2.

While high-speed intracoronary optical coherence tomography (OCT) provides three-dimensional (3D) visualization of coronary arteries in vivo, imaging speeds remain insufficient to avoid motion artifacts induced by heartbeat, limiting the clinical utility of OCT. In this paper, we demonstrate development of a high-speed intracoronary OCT system (frame rate: 500 frames/s, pullback speed: 100 mm/s) along with prospective electrocardiogram (ECG) triggering technology, which enabled volumetric imaging of long coronary segments within a single cardiac cycle (70 mm pullback in 0.7 s) with minimal cardiac motion artifact. This technology permitted detailed visualization of 3D architecture of the coronary arterial wall of a swine in vivo and fine structure of the implanted stent.

We present a synthetic gene circuit for decoupling cell growth from metabolite production through autonomous regulation of enzymatic pathways by integrated modules that sense nutrient and substrate. The two-layer circuit allows Escherichia colito selectively utilize target substrates in a mixed pool; channel metabolic resources to growth by delaying enzymatic conversion until nutrient depletion; and activate, terminate, and re-activate conversion upon substrate availability. We developed two versions of controller, both of which have glucose nutrient sensors but differ in their substrate-sensing modules. One controller is specific for hydroxycinnamic acid and the other for oleic acid. Our hydroxycinnamic acid controller lowered metabolic stress 2-fold and increased the growth rate 2-fold and productivity 5-fold, whereas our oleic acid controller lowered metabolic stress 2-fold and increased the growth rate 1.3-fold and productivity 2.4-fold. These results demonstrate the potential for engineering strategies that decouple growth and production to make bio-based production more economical and sustainable.

Intravascular optical frequency-domain imaging (OFDI), a second-generation optical coherence tomography (OCT) technology, enables imaging of the three-dimensional (3D) microstructure of the vessel wall following a short and nonocclusive clear liquid flush. Although 3D vascular visualization provides a greater appreciation of the vessel wall and intraluminal structures, a longitudinal imaging pitch that is several times bigger than the optical imaging resolution of the system has limited true high-resolution 3D imaging, mainly due to the slow scanning speed of previous imaging catheters. Here, we demonstrate high frame-rate intravascular OFDI in vivo, acquiring images at a rate of 350 frames per second. A custom-built, high-speed, and high-precision fiber-optic rotary junction provided uniform and high-speed beam scanning through a custom-made imaging catheter with an outer diameter of 0.87 mm. A 47-mm-long rabbit aorta was imaged in 3.7 seconds after a short contrast agent flush. The longitudinal imaging pitch was 34 μm, comparable to the transverse imaging resolution of the system. Three-dimensional volume-rendering showed greatly enhanced visualization of tissue microstructure and stent struts relative to what is provided by conventional intravascular imaging speeds.

We demonstrate a novel polarization-sensitive optical frequency domain imaging system employing passive polarization multiplexing. Simple modification of a fiber delay line in the wavelength-swept light source enables illumination with two perpendicular polarizations that are required for determination of the Stokes vector components of the light reflected from each depth of the tissue. This simple all-passive approach provides a robust and low-cost solution for PS imaging replacing relatively complex conventional schemes such as polarization modulation or frequency-encoded polarization multiplexing.