0D/1D Heterojunction Implant with Electro-Mechanobiological Coupling Cues Promotes Osteogenesis

Mimicking the natural bone extracellular matrix containing intrinsic topography and electrical signals is an effective way to modulate bone regeneration. However, simultaneously coupling of the intrinsic mechanobiology and electrical cues of implant to modulate bone regeneration remains ignored. Here, the authors report in situ designation of titanium dioxide (TiO₂) nanocone/bismuth oxide (Bi₂O₃) nanodot heterojunctions on bone implant surface to electro-biomechanically trigger osseointegration at bone/implant interface. TiO₂ nanocone/Bi₂O₃ nanodot heterojunctions exhibit built-in electric field at the nanoscale interface and elastic modulus equivalent to that of bone tissue. The nano-heterojunctions significantly promoted the attachment, spreading, and osteogenic differentiation of bone marrow mesenchymal stem cells in vitro, and the osteogenesis in vivo. The authors also show that the effects of nano-heterojunctions on osteogenesis are mediated by yes-associated protein biomechanical signal pathway and intracellular enrichment induced Phosphatidylinositol 3-kinase signal pathway. Their findings highlight the coupling of topographical and electric parameters of biomaterials for modulating cell behaviors.     

Switching On and Off Macrophages by a “Bridge-Burning” Coating Improves Bone-Implant Integration under Osteoporosis

Osteoporosis poses substantial challenges for biomaterials implantation. New approaches to improve bone-implant integration should resolve the fundamental dilemma of inflammation—proper inflammation is required at early stages but should be suppressed later for better healing, especially under osteoporosis. However, precisely switching on and off inflammation around implants in vivo remains unachieved. To address this challenge, a “bridge-burning” coating material that comprises a macrophage-activating glycan covalently crosslinked by a macrophage-eliminating bisphosphonate to titanium implant surface is designed. Upon implantation, the glycan instructs host macrophages to release pro-osteogenic cytokines (“switch-on”), promoting bone cell differentiation. Later, increasingly mature bone cells secrete alkaline phosphatase to cleave the glycan-bisphosphonate complexes from the implant, which in turn selectively kill the proinflammatory macrophages (“switch-off”) that have completed their contribution—hence in the manner of “burning bridges”—to promote healing. In vivo examination in an osteoporotic rat model demonstrates that this coating significantly enhances bone-implant integration (88.4% higher contact ratio) through modulating local inflammatory niches. In summary, a bioresponsive, endogenously triggered, smart coating material is developed to sequentially harness and abolish the power of inflammation to improve osseointegration under osteoporosis, which represents a new strategy for designing immunomodulatory biomaterials for tissue regeneration.     

Built‐In Electric Fields Dramatically Induce Enhancement of Osseointegration

Rapid and effective osseointegration is a great challenge in clinical practice. Endogenous electronegative potentials spontaneously appear on bone defect sites and mediate healing. Thus, bone healing can potentially be stimulated using physiologically relevant electrical signals in implants. However, it is difficult to directly introduce physiologically relevant electric fields in bone tissue. In this study, built‐in electric fields are established between electropositive ferroelectric BiFeO₃ (BFO) nanofilms and electronegative bone defect walls to trigger implant osseointegration and biological healing. Epitaxial growth technique is used to organize the crystal panel at an atomic scale, and ferroelectric polarization of BFO nanofilms matching the amplitude and direction of endogenous electric potentials on bone defect walls is achieved. In the presence of built‐in electric fields, implants with BFO nanofilms with downward polarization (BFO+) show rapid and superior osseointegration in the rat femur. The mechanism of this phenotypic osteogenic behavior is further studied by protein adsorption and stem cell behavior in different time points. BFO+ promotes protein adsorption and mesenchymal stem cell (MSC) attachment, spreading, and osteogenic differentiation. Custom‐designed PCR array examination shows sequentially initiated Ca²⁺ signaling, cell adhesion and spreading, and PI3K‐AKT signaling in MSCs. The results of this study provide a novel strategy for the development of implant surface modification technology.     

牙种植体系统对种植体周骨吸收影响的临床评价

我国的口腔种植学随着瑞典Branenmrk教授骨整合理论与国际上一些种植体系统的引进而逐渐发展起来,研究主要集中在种植体组织界面、生物力学及种植材料学方面。和传统义齿相比,种植义齿优点明显,被誉为人类的第三副牙齿,受到普遍欢迎。本研究收集种植病例的直接数字化全景片进行测量分析,研究种植体周牙槽骨吸收的情况,以评价种植体系统对骨吸收的影响。实验结果表明,不同的种植体系统对骨吸收的影响没有差异,同一种植体近中、远中也没有差异。本文对实验的测量方法进行了讨论,认为实验结果较为准确地反映了实际情况,并分析了种植体周骨丧失的呵能原因及对策。     

Nano‐Bio‐Chemical Braille for Cells: The Regulation of Stem Cell Responses using Bi‐Functional Surfaces

Insufficient integration with local host tissues is a significant problem that adversely affects the performance of implanted biomedical devices. Poor tissue integration leaves patients susceptible to complications associated with adverse foreign body reactions and infections that typically mandate expensive and elevated‐risk revision surgery. The aging population and growing incidence of medical implants makes the development of bio‐functional implant surfaces a high priority research imperative. Here multifunctional surfaces are reported that are capable of regulating cell adhesion and triggering cell differentiation to facilitate osseointegration of implantable devices. The approach described is universal, cost‐ and time‐effective. It relies on a unique combination of two advances: i) a reactive interface provided by a plasma activated coating (PAC) that covalently immobilises bioactive molecules with significantly higher efficiency than conventional technologies, and ii) multifunctional molecules (bi‐functional fusion‐proteins) that regulate multiple cellular responses. Covalent linking of the molecules, their high density, and desired orientation are demonstrated. The effectiveness of these functional interfaces to regulate mesenchymal stem cell attachment and differentiation is confirmed suggesting the ability to regulate osseointegration. This method is a leap forward in the fabrication of truly biofunctional materials tailored for particular applications.     

Modeling of prosthetic limb rotation control by sensing rotation of residual arm bone

We proposed a new approach to improve the control of prosthetic arm rotation in amputees. Arm rotation is sensed by implanting a small permanent magnet into the distal end of the residual bone, which produces a magnetic field. The position of the bone rotation can be derived from magnetic field distribution detected with magnetic sensors on the arm surface, and then conveyed to the prosthesis controller to manipulate the rotation of the prosthesis. Proprioception remains intact for residual limb skeletal structures; thus, this control system should be natural and easy-to-use. In this study, simulations have been conducted in an upper arm model to assess the feasibility and performance of sensing the voluntary rotation of residual humerus with an implanted magnet. A sensitivity analysis of the magnet size and arm size was presented. The influence of relative position of the magnet to the magnetic sensors, orientation of the magnet relative to the limb axis, and displacement of the magnetic sensors on the magnetic field was evaluated. The performance of shielding external magnetostatic interference was also investigated. The simulation results suggest that the direction and angle of rotation of residual humerus could be obtained by decoding the magnetic field signals with magnetic sensors built into a prosthetic socket. This pilot study provides important guidelines for developing a practical interface between the residual bone rotation and the prosthesis for control of prosthetic rotation.      

Bio-driven system-based virtual reality for prosthetic and rehabilitation systems

Current prosthetic and rehabilitation devices, used for those who are limbless or born with congenital defects or required rehabilitation, are difficult to use. The users have problems to adapt to their new hosts or receiving any bio-feedback despite rehabilitation process and retraining, particularly when working with electromyogram (EMG) signals. In characterizing virtual human limbs, as a potential prosthetic device in three dimensions (3D) virtual reality, patients are able to familiarize themselves with their new appendage and its capabilities or can see their movements’ intention in a Virtual Training Environment. This paper presents a virtual reality (VR)-based design and implementation of a below-shoulder 3D human arm capable of 10-class EMG-based motions driven system of biomedical EMG signal. The method considers a signal classification output as potential control stimulus to drive the virtual limb. A hierarchical design methodology is adopted based on anatomical structure to congruent with virtual reality modeling language (VRML) architecture used in order to progressively build the user interface model and its inherent functionality. The resulting simulation is based on a portable, self-contained VRML prototype implementation paired with an instrumental virtual control-select board capable of actuating any combinations of singular or paired kinematic of 10-class EMG motions. The simulation allows for multiple degree-of-freedom profiles as the classes can be activated independently, or in conjunction with others, allowing enhanced arm movement. Provisions for direct classified control inputs are built into the prototype for holistic system construction.     

EMG and EPP-integrated human-machine interface between the paralyzed and rehabilitation exoskeleton

Although a lower extremity exoskeleton shows great prospect in the rehabilitation of the lower limb, it has not yet been widely applied to the clinical rehabilitation of the paralyzed. This is partly caused by insufficient information interactions between the paralyzed and existing exoskeleton that cannot meet the requirements of harmonious control. In this research, a bidirectional human-machine interface including a neurofuzzy controller and an extended physiological proprioception (EPP) feedback system is developed by imitating the biological closed-loop control system of human body. The neurofuzzy controller is built to decode human motion in advance by the fusion of the fuzzy electromyographic signals reflecting human motion intention and the precise proprioception providing joint angular feedback information. It transmits control information from human to exoskeleton, while the EPP feedback system based on haptic stimuli transmits motion information of the exoskeleton back to the human. Joint angle and torque information are transmitted in the form of air pressure to the human body. The real-time bidirectional human-machine interface can help a patient with lower limb paralysis to control the exoskeleton with his/her healthy side and simultaneously perceive motion on the paralyzed side by EPP. The interface rebuilds a closed-loop motion control system for paralyzed patients and realizes harmonious control of the human-machine system.     

Field distributions in the rat tibia with and without a porousimplant during electrical stimulation: a parameteric modeling

Expeditious post-operative ingrowth of bone is necessary for clinically successful fixation of porous joint prostheses. Electrical or electromagnetic fields to stimulate bone growth into porous implants have been used; however, they produced nonconvincing data. This was partially attributable to the lack of quantification of the localized electric fields produced in the pores of the implants. Therefore, this study set out: i) to quantify the local electric field values induced into the surface pores of nonconducting implants by "capacitive" coupling and to determine the magnitude of the macroscopically applied capacitively coupled electrical currents to induce specific electric field amplitudes in the pores, ii) to identify the important dielectric properties of the implant-tissue interface, and iii) to create the basis for successfully applying electrical fields in an animal model to stimulate bone ingrowth. A finite element method was used to calculate the electric field gradients and current densities present in a rat tibia modeled with a porous intramedullary implant when capacitively stimulated. Results indicated that while the current density in the pores are reduced in comparison to the region just outside the pore by about one order of magnitude, a significant current density still exists in the pore region. Furthermore, the presence of the implant increases the current densities in the trabecular bone while decreasing these values in the cortical bone. Replacing the trabecular bone in the pore by saline increases the current density in the pore by three-fold, but decreases the voltage gradient by a similar factor.     

Variable admittance time-delay control of an upper limb rehabilitation robot based on human stiffness estimation

This paper proposes a new variable admittance time-delay control strategy based on human stiffness estimation for improving the effectiveness of robot-assisted cooperative rehabilitation training. This control strategy is developed and implemented on a planar upper limb rehabilitation robot. Given the minimum-jerk-based desired trajectories of human hand position, in the developed control strategy, a time-delay approximator is utilized to estimate the external disturbances and modeling errors without exact knowledge of dynamics parameters, a sliding mode admittance controller is applied to obtained objective admittance characteristics, and an iterative optimization algorithm is used to estimate human arm stiffness and adjust human-robot interaction compliance. The closed-loop stability of the proposed control method is demonstrated via Lyapunov function theory. Experimental investigations involving ten subjects are conducted to validate the feasibility of the proposed control scheme. The experimental results show that the interaction compliance during cooperative rehabilitation training can be accurately adjusted based on selected admittance parameters and human arm stiffness, and it contributes to satisfying the specific training requirements of patients with different weakness levels and promoting the effectiveness of the robot-assisted training.     

Hydrophobic Coating Platforms for High-Efficiency Loading and Direct Transmembrane Delivery of Fat-Soluble Osteogenic Drug for Enhanced Osseointegration of Titanium Implants

Compared with water-soluble osteogenic drugs, fat-soluble osteogenic drugs exhibit higher bioavailability and drug stability, making them valuable for enhancing the osseointegration of implants. However, existing drug-loading coatings are primarily designed for water-soluble drugs, limiting their effectiveness in loading and delivering fat-soluble osteogenic drugs. This study employed alkali treatment, silanization, and oleic acid acylation to sequentially modify the surface of Ti alloy, aiming to fabricate surfaces capable of efficiently loading and delivering fat-soluble osteogenic drugs. Results show that the hydrophilicity and loading capacity of fat-soluble osteogenic drugs strongly depended on the duration of the acylation treatment. Furthermore, the drug release mechanism involved direct diffusion from the coating to the cells in contact, resulting in improved bioavailability, as opposed to diffusion into the surrounding medium and subsequent cellular uptake. In vitro experiments using vitamine D3 (VD₃) as a model drug confirmed that the coating effectively promoted bone formation through the highly efficient delivery of VD₃. Furthermore, in vivo experiments demonstrated that the VD₃-loaded lipophilic surface significantly enhanced osteogenic capability and improved the osseointegration of titanium implants. This study provides a promising strategy for loading fat-soluble drugs onto Ti implants and direct experimental evidence demonstrating the significant value of fat-soluble drugs in promoting implant osseointegration.     

市售电源插座安全性的综合分析评判

排插直接关系到电器和用户的用电安全.该文详细阐述了各个品牌的排插在4种安全检测中的表现,只有对排插产品有了全面的了解,才能有效抵制劣质排插,提升用电安全.     

Recent development of mechanisms and control strategies for robot-assisted lower limb rehabilitation

Robot-assisted rehabilitation and therapy has become more and more frequently used to help the elderly, disabled patients or movement disorders to perform exercise and training. The field of robot-assisted lower limb rehabilitation has rapidly evolved in the last decade. This article presents a review on the most recent progress (from year 2001 to 2014) of mechanisms, training modes and control strategies for lower limb rehabilitation robots. Special attention is paid to the adaptive robot control methods considering hybrid data fusion and patient evaluation in robot-assisted passive and active lower limb rehabilitation. The characteristics and clinical outcomes of different training modes and control algorithms in recent studies are analysed and summarized. Research gaps and future directions are also highlighted in this paper to improve the outcome of robot-assisted rehabilitation.     

Elastomer chip sockets for reduced thermal mismatch problems and effortless chip replacement, preliminary investigations

To avoid the problem with thermo-mechanical stress induced fatigue using conventional flip-chip mounting of bare chips, an elastic chip socket has been developed. The socket is made by casting silicone elastomer into micro structured silicon molds to form micro bump arrays. After the elastomer is cured and released from the mold, a metal layer is deposited and patterned. A chip is placed in the socket utilizing guiding structures for chip self alignment. The chip is then held in place by a spring loaded back-plate which can also serve as a heat sink for highly effective chip cooling. Since no adhesives, underfills or solders are used, the rework process becomes very simple and it can also be repeated many times for the same socket. Initial contact resistance and thermo-mechanical robustness measurements indicates that this type of sockets could work as a superior replacement for conventional flip-chip technologies in many applications. The particular design of the contact bumps results in metal structures that resemble (although up side down) and are scalable as those in the Chip-First technology. Preliminary thermal shock experiments from room temperature to liquid nitrogen and back show good survival. Thus, this new chip interconnect method indicates the possibility of getting the advantages of the Chip-First technology while eliminating the demand of placing the chip first. The concept will work for chips with rim positioned pads as well as for high density area arrays.     

Residual damage effects on gate contacts formed on SiC surfaces etched by using the amorphization technique

A trench fabrication process has been proposed and experimentally demonstrated for silicon carbide using the amorphization technique. In the present work, the quality of gates [oxide for metal oxide semiconductor field-effect transistors (MOSFETs) and Schottky barrier contacts for metal semicondcutor field-effect transistors (MESFETs)] fabricated on the etched surfaces are compared with those formed on the as-grown silicon carbide surface. The resistivity and breakdown electric field of the thermal oxide grown on the etched surface was found to be comparable to that of thermal oxide grown on silicon. However, a large concentration of acceptor type interface states (0.5-1 x 10¹³ cm⁻²eV⁻¹) was observed. This results in a large negative interface charge at room temperature and a significant shift in flat band voltage as a function of temperature, which makes the process unsuitable for formation of gates in UMOSFETs. Titanium Schottky contacts formed on the etched surface showed superior reverse current-voltage characteristics and higher breakdown voltages than the Schottky diodes formed on unetched surface with similar doping concentrations. This indicates that the argon implant process for trench formation is suitable for fabrication of gate regions in high voltage vertical MESFETs (or SITs).     

A new approach for characterizing structure-dependent hot-carriereffects in drain-engineered MOSFET's

In this paper, we have demonstrated successfully a new approach for evaluating the hot-carrier reliability in submicron LDD MOSFET with various drain engineering. It was developed based on an efficient charge pumping measurement technique along with a new criterion. This new criterion is based on an understanding of the interface state (N_it ) distribution, instead of substrate current or impact ionization rate, for evaluating the hot-carrier reliability of drain-engineered devices. The position of the peak N_it distribution as well as the electric field distribution is critical to the device hot-carrier reliability. From the characterized N_it spatial distribution, we found that the shape of the interface state distribution is similar to that of the electric field. Also, to suppress the spacer-induced degradation, we should keep the peak values of interface state away from the spacer region. In our studied example, for conventional LDD device, sidewall spacer is the dominant damaged region since the interface state in this region causes an additional series resistance which leads to drain current degradation. LATID device can effectively reduce hot-carrier effect since most of the interface states are generated away from the gate edge toward the channel region such that the spacer-induced resistance effect is weaker than that of LDD devices     

NeXOS – The design,development and evaluation of a rehabilitation system for the lower limbs

Recent years have seen the development of a number of automated and semi-automated systems to support physiotherapy and rehabilitation. These deploy a range of technologies from highly complex purpose built systems to approaches based around the use of industrial robots operating either individually or in combination for applications ranging from stroke rehabilitation to mobility enhancement. The NeXOS project set out to investigate an approach to the rehabilitation of the lower limbs in a way which brought together expertise in engineering design and mechatronics with specialists in rehabilitation and physiotherapy.The result is prototype of a system which is potentially capable in operating in a number of modes from fully independent to providing direct support to a physiotherapist during manipulation of the limb. Designed around a low cost approach for an implementation ultimately capable of use in a patients home using web-based strategies for communication with their support team, the prototype NeXOS system has validated the adoption of an integrated approach to its development. The paper considers this design and development process and provides the results from the initial tests with physiotherapists to establish the operational basis for clinical implementation.     

Residual stress in hydroxyapatite coating: nonlinear analysis and high-energy synchrotron measurements

The thermal deposition of hydroxyapatite (HA) on titanium alloy substrate (Ti-6A1-4V) leads to a structure that has very good osseointegration properties. However, clinical failures have been occasionally reported at the interface between substrate and coating. Lifetime is the main parameter in such prostheses; therefore, in order to improve their quality, it is necessary to evaluate the level of stresses near the interface. The high-energy synchrotron radiation combines the advantages of a bulk analysis and reduced volume of the gauge. The objective of our study was to calculate the residual stress using a nonlinear finite-element model and to measure residual stress level near the interface, in the hydroxyapatite coating and in titanium alloy substrate with a nondestructive and high-resolution experiment. The high-energy synchrotron radiation of the BM16 beam-line at ESRF (Grenoble-France) was used with a resolution of down to 10 micrometers. The experimental measurements validate the results found by means of nonlinear finite-element analysis of the plasma spraying induced stress.     

A Novel Bonding Method for Ionic Wafers

A novel method for bonding sapphire, quartz, and glass wafers with silicon using the modified surface activated bonding (SAB) method is described. In this method, the mating surfaces were cleaned and simultaneously coated with nano-adhesion Fe layers using a low energy argon ion beam. The optical images show that the entire area of the 4-in wafers of LiNbO₃/Si was bonded. Such images for other samples show particle induced voids across the interface. The average tensile strength for all of the mating pairs was much higher than 10 MPa. Prolonged irradiation reduced polarization in sapphire, quartz, and Al-silicate glasses. Fe and Ar ion-induced charge deposition result in the formation of an electric field, which was responsible for the depolarization. The lattice mismatch induced local strain was found in LiNbO₃/Si. No such strain was observed in the Al-silicate glass/Si interface probably because of annealing at 300 for 8 h. The Al-silicate glass/Si interface showed an interfacial layer of 2 nm thick. A 5-nm-thick amorphous layer was observed with the other layer across the /Si interface. The EELS spectra confirmed the presence of nano-adhesion Fe layers across the interface. These Fe layers associated with the electric field induced by ion beam irradiation for prolonged period of time, particularly in LiNbO₃/Si, might be responsible for the high bonding strength between Si/ionic wafers at low temperatures.     

A flexible ATM-host interface for XUNET II

An asynchronous transfer mode (ATM)-based host interface for the XUNET II experimental wide area network is described. The interface is flexible, and its software is easy to program and modify. The hardware implementation of the interface, which resembles a conventional single-board computer, and the programming model of the interface are described. The results of performance measurements of the interface taken at a number of levels are presented. Some recently proposed host interface designs that use the criteria of flexibility, simplicity, accessibility, and compatibility with the Berkeley Software Distribution (BSD) socket interface are outlined