The Influence of Electron Beam Sterilization on In Vivo Degradation of β-TCP/PCL of Different Composite Ratios for Bone Tissue Engineering.

We evaluated the effect of electron beam (E-beam) sterilization (25 kGy, ISO 11137) on the degradation of β-tricalcium phosphate/polycaprolactone (β-TCP/PCL) composite filaments of various ratios (0:100, 20:80, 40:60, and 60:40 TCP:PCL by mass) in a rat subcutaneous model for 24 weeks. Volumes of the samples before implantation and after explantation were measured using micro-computed tomography (micro-CT). The filament volume changes before sacrifice were also measured using a live micro-CT. In our micro-CT analyses, there was no significant difference in volume change between the E-beam treated groups and non-E-beam treated groups of the same β-TCP to PCL ratios, except for the 0% β-TCP group. However, the average volume reduction differences between the E-beam and non-E-beam groups in the same-ratio samples were 0.76% (0% TCP), 3.30% (20% TCP), 4.65% (40% TCP), and 3.67% (60% TCP). The E-beam samples generally had more volume reduction in all experimental groups. Therefore, E-beam treatment may accelerate degradation. In our live micro-CT analyses, most volume reduction arose in the first four weeks after implantation and slowed between 4 and 20 weeks in all groups. E-beam groups showed greater volume reduction at every time point, which is consistent with the results by micro-CT analysis. Histology results suggest the biocompatibility of TCP/PCL composite filaments

Lithium niobate micromachining for the fabrication of microfluidic droplet generators

In this paper, we present the first microfluidic junctions for droplet generation directly engraved on lithium niobate crystals by micromachining techniques, preparatory to a fully integrated opto-microfluidics lab-on-chip system. In particular, laser ablation technique and the mechanical micromachining technique are exploited to realise microfluidic channels in T-and cross junction configurations. The quality of both lateral and bottom surfaces of the channels are therefore compared together with a detailed study of their roughness measured by means of atomic force microscopy in order to evaluate the final performance achievable in an optofluidic device. Finally, the microfluidics performances of these water-in-oil droplets generators are investigated depending on these micromachining techniques, with particular focus on a wide range of droplet generation rates

Fabrication of micro-structures for optically driven micromachines using two-photon photopolymerization of UV curing resins

Two-photon photopolymerization of UV curing resins is an attractive method for the fabrication of microscopic transparent objects with size in the tens of micrometers range. We have been using this method to produce three-dimensional structures for optical micromanipulation, in an optical system based on a femtosecond laser. By carefully adjusting the laser power and the exposure time we were able to create micro-objects with well-defined 3D features and with resolution below the diffraction limit of light. We discuss the performance and capabilities of a microfabrication system, with some examples of its products.Comment: 12 pages, 10 figure

A Wireless Implantable System for Facilitating Gastrointestinal Motility.

Gastrointestinal (GI) electrical stimulation has been shown in several studies to be a potential treatment option for GI motility disorders. Despite the promising preliminary research progress, however, its clinical applicability and usability are still unknown and limited due to the lack of a miniaturized versatile implantable stimulator supporting the investigation of effective stimulation patterns for facilitating GI dysmotility. In this paper, we present a wireless implantable GI modulation system to fill this technology gap. The system consists of a wireless extraluminal gastrointestinal modulation device (EGMD) performing GI electrical stimulation, and a rendezvous device (RD) and a custom-made graphical user interface (GUI) outside the body to wirelessly power and configure the EGMD to provide the desired stimuli for modulating GI smooth muscle activities. The system prototype was validated in bench-top and in vivo tests. The GI modulation system demonstrated its potential for facilitating intestinal transit in the preliminary in vivo chronic study using porcine models

On-chip inverted emulsion method for fast giant vesicle production, handling, and analysis

Liposomes and giant unilamellar vesicles (GUVs) in particular are excellent compartments for constructing artificial cells. Traditionally, their use requires bench-top vesicle growth, followed by experimentation under a microscope. Such steps are time-consuming and can lead to loss of vesicles when they are transferred to an observation chamber. To overcome these issues, we present an integrated microfluidic chip which combines GUV formation, trapping, and multiple separate experiments in the same device. First, we optimized the buffer conditions to maximize both the yield and the subsequent trapping of the vesicles in micro-posts. Captured GUVs were monodisperse with specific size of 18 ± 4 µm in diameter. Next, we introduce a two-layer design with integrated valves which allows fast solution exchange in less than 20 s and on separate sub-populations of the trapped vesicles. We demonstrate that multiple experiments can be performed in a single chip with both membrane transport and permeabilization assays. In conclusion, we have developed a versatile all-in-one microfluidic chip with capabilities to produce and perform multiple experiments on a single batch of vesicles using low sample volumes. We expect this device will be highly advantageous for bottom-up synthetic biology where rapid encapsulation and visualization is required for enzymatic reactions

Editorial for the Special Issue on Micro/Nano-Chip Electrokinetics, Volume II

There has been a rapidly increasing interest in the use of micro/nanofluidics to develop various point-of-care technologies for global health [1,2]. Electrokinetics is often the method of choice in these micro/nano-chips for an accurate transport and manipulation of fluids and samples [3,4]. This special issue in Micromachines is the continuation of our successful first volume on Micro/Nano-Chip Electrokinetics [5]. It consists of 22 contributions, which cover multiple aspects of electrokinetics related phenomena for various chemical and biological applications. We divide these papers into three primary categories and summarize them briefly below

Ultra-Stretchable Interconnects for High-Density Stretchable Electronics

The exciting field of stretchable electronics (SE) promises numerous novel applications, particularly in-body and medical diagnostics devices. However, future advanced SE miniature devices will require high-density, extremely stretchable interconnects with micron-scale footprints, which calls for proven standardized (complementary metal-oxide semiconductor (CMOS)-type) process recipes using bulk integrated circuit (IC) microfabrication tools and fine-pitch photolithography patterning. Here, we address this combined challenge of microfabrication with extreme stretchability for high-density SE devices by introducing CMOS-enabled, free-standing, miniaturized interconnect structures that fully exploit their 3D kinematic freedom through an interplay of buckling, torsion, and bending to maximize stretchability. Integration with standard CMOS-type batch processing is assured by utilizing the Flex-to-Rigid (F2R) post-processing technology to make the back-end-of-line interconnect structures free-standing, thus enabling the routine microfabrication of highly-stretchable interconnects. The performance and reproducibility of these free-standing structures is promising: an elastic stretch beyond 2000% and ultimate (plastic) stretch beyond 3000%, with 10 million cycles at 1000% stretch with <1% resistance change. This generic technology provides a new route to exciting highly-stretchable miniature devices.Comment: 13 pages, 5 figure, journal publicatio

Towards efficient modelling of optical micromanipulation of complex structures

Computational methods for electromagnetic and light scattering can be used for the calculation of optical forces and torques. Since typical particles that are optically trapped or manipulated are on the order of the wavelength in size, approximate methods such as geometric optics or Rayleigh scattering are inapplicable, and solution or either the Maxwell equations or the vector Helmholtz equation must be resorted to. Traditionally, such solutions were only feasible for the simplest geometries; modern computational power enable the rapid solution of more general--but still simple--geometries such as axisymmetric, homogeneous, and isotropic scatterers. However, optically-driven micromachines necessarily require more complex geometries, and their computational modelling thus remains in the realm of challenging computational problems. We review our progress towards efficient computational modelling of optical tweezers and micromanipulation, including the trapping and manipulation of complex structures such as optical micromachines. In particular, we consider the exploitation of symmetry in the modelling of such devices.Comment: 5 pages, 4 figure