Bipolar Design Research Articles

Multi-Dimensional Modelling of Bioinspired Flow Channels Based on Plant Leaves for PEM Electrolyser

The Polymer Electrolyte Membrane Water Electrolyser (PEMWE) has gained significant interest among various electrolysis methods due to its ability to produce highly purified, compressed hydrogen. The spatial configuration of bipolar plates and their flow channel patterns play a critical role in the efficiency and longevity of the PEM water electrolyser. Optimally designed flow channels ensure uniform pressure and velocity distribution across the stack, enabling high-pressure operation and facilitating high current densities. This study uses flow channel geometry inspired by authentic vine leaf patterns found in biomass, based on various plant leaves, including Soybean, Victoria Amazonica, Water Lily, Nelumbo Nucifera, Kiwi, and Acalypha Hispida leaves, as a novel channel pattern to design a PEM bipolar plate with a circular cross-section area of 13.85 cm2. The proposed bipolar design is further analysed with COMSOL Multiphysics to integrate the conservation of mass and momentum, molecular diffusion (Maxwell–Stefan), charge transfer equations, and other fabrication factors into a cohesive single-domain model. The simulation results showed that the novel designs have the most uniform velocity profile, lower pressure drop, superior pressure distribution, and heightened mixture homogeneity compared to the traditional serpentine models.

Retinomorphic Color Perception Based on Opponent Process Enabled by Perovskite Bipolar Photodetectors.

The ability to perceive color by the retina can be attributed to both its trichromatic photoreceptors and the antagonistic neural wiring known as the opponent process. While neuromorphic sensors have been shown to demonstrate memory and adaptation capabilities, color perception is still challenging due to the intrinsic lack of spectral selectivity in narrow bandgap semiconductors. Furthermore, research on emulating neural wiring is severely lacking. The combination of halide perovskite materials with a tunable bandgap and a novel bipolar photodetector design emulates the efficiency of the retina in processing color information. The stimuli-responsive material is also responsible for maintaining partial color constancy-an adaptation feature. Leveraging the unique enhancement of color contrasts, an in-sensor data compression and edge detection can also be demonstrated. The color perception, chromatic adaptation, and color contrast enhancement make perovskite bipolar photodetectors a unique example where the sensor and neural wiring can be co-developed in conjunction.

Polychromatic electrochromic films via bipolar covalent organic framework design

Because of the ordered and loose structure, covalent organic framework (COF) holds broad promise in the field of electrochromism, but the simple color change limits its application and development. A bipolar and polychromatic COF-GZU1 was successfully designed and prepared in this paper. The structure, electrostatic potential and orbital structure of the COF-GZU1 were predicted and calculated using density functional theory, and the calculation results confirmed the feasibility of bipolar construction strategy. XRD, SEM, BET and GIWAXS further mutually established the successful synthesis of COF-GZU1, which exhibited high specific surface area, crystallinity and porosity. Results from electrochemical impedance spectroscopy, density of states analysis, and ion diffusion coefficient measurements verified that the ordered porous structure facilitates electron conduction and ion mass transfer, leading to a significant improvement in electrochromic performance. Moreover, the COF-GZU1 film displayed excellent electrochromic performance, providing polychromatic switching with a rapid response time (7.8/14.5 s and 1.0/12.6 s for coloring/bleaching process) and high coloring efficiency (112.8 and 127.8 cm2∙C-1 at 799 and 570 nm). These results collectively demonstrate the superiority of the COF-GZU1 film and suggest that the bipolar COF design strategy could pave the way for new and high-performance polychromatic electrochromic materials.

(Invited) Shunt-currents in Alkaline Water-Electrolyzers and Renewable Energy

Shunt-currents in bipolar cell stack design with a common electrolyte-feed and -outlet is an inevitable physical phenomenon governed by Ohms law that causes some extra challenges when alkaline water-electrolysers shall operate on renewable energy that is both dynamic and intermittent. Shunt-currents are also referred to as bypass-current or creep-current. The shunt-currents are to much degree governed by the electrolyte inside the cell stack manifold system that transports lye in and out of the cells. The electrolyte inside the manifold system also electrically connects the individual cells together and enables transport of ions/electricity in parallel to the cell stack. Thus, a small portion of the rectifier current is being shunted outside the cells and does not contribute to any production. Previous work on shunt-current modelling brought new insight on how to design the manifolds and raised the awareness on shunt-current and the use of metallic manifolds which both reduced the ohmic resistivity of the manifold system and was a source of secondary electrolysis.Classic alkaline water-electrolysers are typically using an internal manifold system where the inlet ports are located at the bottom of the cell stack and the outlet ports are located at the top, and where the ports connecting the cell-interior and the common manifold channel are short and straight. Such design has in the past worked satisfactory for alkaline water-electrolysers that have been working on a high nominal load and only being shut-down for maintenance a few times over the stack-lifetime, mainly causing a modest reduction in the current efficiency. Membrane-chlorine electrolysers on the other hand, are designed for very small shunt-currents by using an external manifold system, which enables a current protection system that protects electrodes from corrosion under shutdown conditions.Shunt-currents bypassing the cell stack does not contribute to any product and therefore constitutes a loss in current efficiency and, hence, an accordingly loss in the energy efficiency (the shunt-currents still adds to the electricity bill). The atmospheric alkaline electrolyser has a modest loss in current efficiency at nominal load where the high gas volume blocks much of the current path in the rather open outlet ports. The high-pressure alkaline electrolysers on the other hand, where the gas volumes are much smaller, the current efficiency can be as low as 89% at nominal load due to shunt-currents when using simple internal manifold system. For an electrolyser with already low current efficiency at the nominal load, the current efficiency will drop dramatically as the electrolyser is taken to lower load, severely compromising the energy efficiency. The impact on shunt-currents also dramatically increases for increased number of cells in a cell stack, and eventually limits the number of cells that can be assembled in one single cell stack operating on the same common lye system.Shutdown and discharge of the electrodes may further lead to corrosion and degradation of the electrodes, strongly influenced by the shunt-currents and the manifold system. Large cell stacks will discharge faster and deeper, eventually causing corrosion of the electrodes. As the cell stack is discharged the current in the cell stack is reversed where the hydrogen electrode is being polarized to anodic potentials, and the oxygen electrode is polarized to low cathodic potentials which eventually may challenging the material stability. Thus, evaluation of electrode potentials must be an integral part of development of industrial electrodes [LeRoy] and especially in intermittent operation where frequent shutdown will occur. A good integration of the manifold system into the cell stack can potentially mitigate both the loss of current efficiency under dynamic operation and the electrode corrosion under intermittent operation.

Design and Manufacturing Challenges in PEMFC Flow Fields—A Review

Proton exchange membrane fuel cells are a prime choice for substitute electricity producers. Membrane electrode assembly (MEA), bipolar electrodes, and current collectors belong to only a limited number of primary parts of the proton exchange membrane fuel cell (PEMFC). Bipolar plates are among the most famous elements in the fuel cell; they are responsible for the electrochemical reaction, as well as the flow of gases from one bipolar plate to another. A bipolar plate is to be a good electro-conducting, non-corrosive, and a high mechanical strength product. The attainability of the specification is achieved by graphite and metallic materials, each one having its own merits and demerits that are discussed in this article. Likewise, making the second pass for the flow pattern is equally important for the cell to have good performance and efficiency. The emergence of innovative and new bipolar plate designs has caused the achievement of high performance of these plates. The present review article principally focuses on the experimental study of diverse flow fields in the design of PEMFC and on the influence of various geometrical properties on the general operation of fuel cells made of PEMFC, and also on the manufacturing procedure utilized for building contemporary fuel cells.

Numerical simulation analysis of composite flow field design on mass transfer in proton exchange membrane fuel cell

Bipolar plate flow field design is crucial for optimizing Proton Exchange Membrane Fuel Cell (PEMFC) performance. This study employs three-dimensional simulations and Computational Fluid Dynamics (CFD) methods to analyze and compare traditional Straight Parallel Flow Field (SPFF), Block Incorporated Flow Field (BIFF), Sub-channel Ribbed Flow Field (SRFF), and Combined Block and Sub-channel Flow Field (CBSFF). The findings indicate that CBSFF not only demonstrates superior oxygen distribution characteristics at high current densities but also shows improved uniformity in moisture and temperature distribution. In addition, the effect of the structural parameters of the CBSFF flow field on its performance has been investigated. In particular, at a voltage of 0.5 V, the net power of the CBSFF is increased by 18 percent compared with that of the SPFF when the height of the block, hb=0.5, and the height of the subchannel, hs=0.3, are used.

Bipolar Plate Design Assessment: Proton Exchange Membrane Fuel Cell and Water Electrolyzer

ABSTRACTProton exchange membrane fuel cells (PEMFCs) as power generators and proton exchange membrane water electrolyzers (PEMWEs) as hydrogen fuel producers play critical roles in implementing hydrogen energy. The bipolar plates (BPPs) in both PEMFC and PEMWE facilitate the distribution of reactants and products, providing electrical connectivity in a series of singular cells. Although both systems are categorized under the same PEM spectrum, the differing reaction mechanisms require specialized plate properties to achieve optimum performance. This short review analyzes the characteristics of BPPs in both PEMFC and PEMWE, with a focus on the plate material, coating, and flow field. This short review concluded that the polymer composite graphite–based BPPs are the most feasible for PEMFC with no coating needed. PEMWE needs SS316 as a BPP material with a conductive coating to withstand the highly corrosive oxygen evolution reaction at the anode. The serpentine flow field showed dominance in PEMFC stack performance due to even fluid distribution and efficient liquid water drainage. However, its high‐pressure drop contributes to greater parasitic power. PEMWEs commonly adopt the parallel flow field for its lower contact resistance and bubble formation for efficient mass transport toward the cathode.

Comparative study on air-cooled fuel cell stacks with metal and graphite bipolar plate designs for unmanned aerial vehicles

The proton exchange membrane fuel cell (PEMFC) power source is a promising solution for the unmanned aerial vehicles (UAVs) to extend the flight endurance. However, the light weighted PEMFC stack design with improved performance remains a critical challenge for the UAVs applications. In this study, two air-cooled PEMFC stacks based on metal and graphite bipolar plates are designed respectively to optimize the fuel cell power density with comparative tests and simulations under varied operating conditions. The designed metal and graphite stacks could reach the power densities of 1189 W/kg and 792 W/kg, of which the graphite one is integrated in a hybrid power system for the UAVs and operated for a flight test with ∼45 min. Validated by the experiment, a three-dimensional coupled model is developed to comparatively study the internal performance and thermal behaviors of the two stacks. Compared with the graphite stack, the metal one outputs higher voltage by 4 %, weighs lighter by 31 % and improves air forced thermal dissipation with enhanced water retention ability. The proposed model and comparative analysis reveal the mechanisms of stack performance variation under different designs and operations, which are beneficial for the optimization of UAVs fuel cell power system.

Does the polarity of radial head arthroplasty affect functional outcomes? A systematic review and meta-analysis.

Radial head arthroplasty allows a high degree of customizability, and implant polarity has emerged as an important variable. The purpose of this meta-analysis was to evaluate differences in functional and clinical outcomes between patients receiving monopolar and bipolar radial head prosthetic implants. A systematic review and meta-analysis were employed, and 65 articles were identified in three databases. Twelve articles contained non-English or insufficient text and were consequently excluded, and 20 others did not contain sufficient data or follow-up. The remaining 33 articles were qualitatively and quantitatively reviewed. In total, 33 populations were identified, with 809 unduplicated patients: 565 with monopolar and 244 with bipolar implants. In these respective patients, the mean follow-up was 40.2 and 56.9 months. Average Mayo Elbow Performance Score were 86.7 and 87.4 (P=0.80), respectively; average Disability of the Arm, Shoulder, and Hand scores were 17.9 and 14.7 (P=0.47), and average final flexion/extension arcs were 119.4° and 118.7° (P=0.48). Revision rates were 4.07% and 6.56%, while complication rates were 19.65% and 20.08% in the respective monopolar and bipolar patients. These increased relative risks associated with bipolar implants were not significant. Radial head implant polarity does not appear to affect functional outcomes. While bipolar prosthetic design may increase the risks of revision and complications, the increases were not significant. Level of evidence: IV.

Ti-mesh bipolar plate design and optimization for enhanced PEM electrolyzer performance in water splitting

Proton exchange membrane (PEM) electrolyzers are promising devices for hydrogen production from water splitting, but their performance and stability are still limited by various factors. This paper studies the effects of different structures on the performance of PEM electrolyzers, focusing on the working temperature, water conductivity, and the structure of bipolar plate. The results show that higher temperature and lower water conductivity enhance the electrolyzer performance, by increasing the catalyst activity and the proton transport. Moreover, a novel structure using a platinum-coated titanium mesh-based bipolar plate is proposed and tested. This structure improves the performance of the electrolyzer, by optimizing the mass transport, pressure drop, and water management in the electrolyzer. A 23-cell electrolyzer with this structure is developed and demonstrated. The electrolyzer achieves a high performance and stability, with a cell voltage of 1.742 V, a voltage efficiency of 85.0%, and a hydrogen production rate of 1.14 Nm3/h at 0.99 A/cm2. The observed cell voltage for the PEM electrolyzer is consistent with the documented range, typically spanning from 1.55 to 1.90 V at a current density of 0.99 A/cm2. This suggests that our bipolar plate design simplifies PEM electrolyzer manufacture while maintaining comparable performance to existing electrolyzers.

Efficiency Roll-off Suppression in Solution-Processed Organic Light-Emitting Diodes through a Bipolar Host Design

Efficiency Roll-off Suppression in Solution-Processed Organic Light-Emitting Diodes through a Bipolar Host Design

Review on high‐performance polymeric bipolar membrane design and novel electrochemical applications

AbstractElectrochemical devices allow the conversion and storage of renewable energy into high‐value chemicals to mitigate carbon emissions, such as hydrogen production by water electrolysis, carbon dioxide reduction, and the electrochemical synthesis of ammonia. Independent regulation of the electrode pH environment is essential for optimizing the electrode reaction kinetics and enriching the catalyst species. The in situ water dissociation (WD, ) in bipolar membranes (BPMs) offers the possibility of realizing this pH adjustment. Here, the design principles of high‐performance polymeric BPMs in electrochemical device applications are presented by analyzing and connecting WD principles and current–voltage curves. The structure–transport property relationships and membrane durability, including the chemical and mechanical stability of the anion‐ and cation‐exchange layers as well as the integrality of the interfacial junction, are systematically discussed. The advantages of BPMs in new electrochemical devices and major challenges to break through are also highlighted. The improved ion and water transport in the membrane layer and the minimized WD overpotential and ohmic loss at high current densities are expected to facilitate the promotion of BPMs from conventional chemical production to novel electrochemical applications.

Development of fiber reinforced compound bipolar foils for fuel cells

In the research project "InduRex", the challenge was to produce graphite polymer bipolar plates with the thinnest possible thickness. The physical and chemical requirements were defined according to the values set by the "Department of Energy". Within the scope of the project, the continuous production of highly filled foils, which were then successfully structured as bipolar foils and operated in a fuel cell, was successfully implemented. Initial cell tests demonstrated a good cell efficiency at low and medium current densities. For this reason, the approach of creating bipolar plates from compound foils is still being pursued. Now the challenge is to produce bipolar films with a larger active area and to increase the mechanical stability to such an extent that the construction of a multicell stack can be realized. As a result, a metallic bipolar plate design was successfully transferred to a compound foil as part of the "InduRex" project. The problem is that with a larger bipolar foil there is a risk of obtaining low mechanical stability. Therefore, carbon fibers are introduced into the films as part of the research project "Faserverstaerkte Folien" in order to improve the mechanical properties. In addition to continuous production, the thin-walled foils are reinforced with carbon fibers using a hot press. The fiber-reinforced foils will be characterized in the next steps to investigate the influence of the carbon fibers. The aim is to obtain even thinner bipolar plates with consistent properties from the extruded foils in order to reduce the overall weight and volume of the fuel cell.

Performance comparison of bio-inspired flow field designs for direct methanol fuel cell and proton exchange membrane fuel cell

Bipolar flow channel plate design, which is a key component and performance qualifier of fuel cells, is an extensively investigated area. Recently, bio-inspired flow fields (FFs) have been designed to increase the overall performance as an alternative to traditional FFs. In the present study, performance evaluation of the various bio-inspired FFs was carried out in PEM fuel cell and direct methanol fuel cell modes. The effects of the main performance characteristics including the clamping force of the short stack assembly, air flow rate, and operating temperature on the cell power were investigated for both PEMFC and DMFC modes. The highest performance output was ensured with the Morus leaf-inspired FF (MLFF) at PEMFC mode at 55 °C with a peak power density of 313 mW/cm2. Besides, the highest performance for DMFC mode was achieved at 35.8 mW/cm2 with the Ficus Carica leaf-inspired FF (FCLFF).

Lightweight and Efficient: Exploring Low-Weight Bipolar Plates for Alkaline PEM Fuel Cells

Alkaline proton exchange membrane (PEM) fuel cells have the potential to be highly efficient and environmentally sustainable energy sources. However, the performance and durability of these fuel cells are dependent to some extent on the bipolar plates used in their design. Bipolar plates play a crucial role in the electrochemical reactions within the fuel cell, and their design and material selection can greatly impact the efficiency and lifespan of the fuel cell.This study focuses on three key aspects of developing efficient and durable bipolar plates for alkaline PEM fuel cells. Firstly, the study emphasizes the importance of optimizing bipolar plate design and flow field to enhance the power output and limiting current density of the fuel cell. Computational fluid dynamics (CFD) simulations are employed to optimize the flow field design, which is found to be crucial in determining the performance of the fuel cell. The optimized flow field design enhances the current density and reduces the pressure drop, resulting in improved fuel cell efficiency.Secondly, the study investigates the potential of low-weight bipolar plates made with printed circuit boards (PCBs) as the matrix material. Traditional bipolar plates made with graphite or metal are often heavy and bulky, leading to increased material costs and decreased fuel cell efficiency. The use of PCBs as the matrix material results in a significant reduction in weight compared to traditional materials, without sacrificing performance. However, the alkaline environment in fuel cells can cause significant corrosion damage to the bipolar plates over time. To mitigate this issue, the PCBs are coated with a layer of Ni-P electroless coating to protect against corrosion.Thirdly, the study examines the effectiveness of corrosion protection measures using Ni-P electroless coating. The electroless coating significantly improves the corrosion resistance of the bipolar plates, thereby prolonging their lifespan and maintaining the performance of the fuel cell over time. The combination of low-weight bipolar plates made with PCBs and corrosion protection measures using Ni-P electroless coating has the potential to enhance the overall performance and durability of alkaline PEM fuel cells.Overall, this study highlights the importance of considering bipolar plate design, material selection, and corrosion protection measures in developing efficient and durable alkaline PEM fuel cells. The optimized flow field design enhances the current density and reduces the pressure drop, while the use of PCBs as the matrix material and Ni-P electroless coating as the corrosion protection measure significantly improve the fuel cell's efficiency and lifespan. These findings provide valuable insights for the development of next-generation fuel cells that are both high-performing and environmentally sustainable.

A Mathematical Model for the Membrane Electrode Assembly of a Bicarbonate Electrolyzer

Bicarbonate electrolyzers are devices designed to convert CO2 released in situ from bicarbonate ions into chemicals and fuels without an external source of CO2 gas. A one-dimensional steady-state isothermal model is developed for the membrane electrode assembly of a bicarbonate CO2 electrolyzer with a bipolar membrane design. The model incorporates species transport in both the anode and cathode electrodes due to convection, diffusion, and migration, and accounts for the catalyzed water splitting reaction at the interface of the anion exchange layer and the cation exchange layer of the bipolar membrane. A direct comparison of model simulations with available experimental data shows that the model can accurately simulate measured Faradaic efficiency and CO yield for all operating current densities. The model can also accurately simulate most of the polarization curve, with the only limitation being in the range dominated by mass transport. Compared to the other parameters studied in this paper, numerical results show that the performance of the bicarbonate CO2 electrolyzer is more sensitive to both aqueous electrolyte saturation in the cathode catalyst layer and the catalyzed water splitting efficiency of the bipolar membrane.

Midterm outcomes of a short-cemented bipolar radial head arthroplasty, in a cohort of 56 cases with minimum 2-years follow-up

BackgroundRadial head prostheses are used in comminuted radial head fractures for elbow stabilisation when reduction and internal fixation is not possible. Several implant designs exist, but no large series exist about a short-cemented and bipolar implant. HypothesisThe hypothesis was that this prosthesis design shows good clinical, functional, and radiological results, with acceptable rate of complications. Study designThis retrospective study included the prostheses with bipolar design and short-cemented stem (Evolutive™), with a minimum 2-years follow-up. Materials and methodsAll prosthesis implanted in our Traumatology Center were included, with minimum 2-years follow-up. The evaluation consisted of a clinical and functional evaluation, associated with an independent radiographic assessment. All complications were listed, as long as rate and reasons for implant removal. ResultsFifty-six implants were studied with a mean follow-up of 64.9months (24 to 119). Fifty-three cases were acute injuries with 16% isolated radial head fractures and 76% complex elbow injury such as ulno-humeral, radio-ulnar or longitudinal forearm instability. Fifty (89%) implants were still in place at last follow-up. The main reason for implant removal was during arthrolysis procedure. Ranges of motion were: 126° in flexion, 9° of extension loss, 76° of pronation and 79° of supination. Mean Mayo Elbow Performance Index was 84.1 with 72% of excellent or good results, and the median quick-DASH was rated 18.2. Radiographic evaluation found 12% significant ulno-humeral arthtitis, 64% capitellar osteopenia and 12% loosening. We recorded 5% of implant-related complications. DiscussionThe short-cemented stem bipolar radial head prosthesis presents clinical and functional results similar to other radial head prosthesis with low incidence of elbow arthritis, when treating both isolated radial head fracture or complexes elbow injury. This implant should therefore be valid for treating comminuted radial head fractures in all types of traumatological injuries. Level of evidenceIV; Retrospective cohort study.

Development of proton exchange membrane fuel cell flow plate geometry design

The advancement of bipolar plate technology can potentially make hydrogen fuel cells more viable as a part of renewable energy system. Two new bipolar plate designs were developed and compared with a reference channel in this study. Compared to the reference channel, the rectangular and hexagonal baffle designs performed significantly better. The rectangular design demonstrated better reactant distribution and fewer dead zones than the hexagonal design, resulting in higher current and power densities. The rectangular baffle design's operating conditions were improved by increasing pressure, temperature, humidity, and adding cooling channels to the anode and cathode. Power and current output were significantly increased as a result of this optimization.

Faster bipolar capacitive deionization with flow-through electrodes

Capacitive deionization (CDI) is an emerging technology in water cleaning applications. Bipolar electrode modules are promising for upscaling CDI systems by applying a high voltage over a stack of cells. Previous experiments indicate around 3 times faster removal rate can be achieved with a 5-cell stack of flow-between electrodes. In this work, we present the first flow-through bipolar CDI design. Surprisingly, the effective average salt adsorption rate (ASAR) of a 5-cell stack was around 10 times higher per electrode mass. The flow-through design allows for faster ion transport to match the higher charging rate. Also, the floating electrodes discharge near-instantaneous by internal short-circuit upon the removal of potential, leaving almost twice as much time for charging in a cycle. Resistance is lowered due to the removal of internal compartments in the design, and the benefits of flow-through devices outweigh any potential higher energy cost of mass transport. The high voltage at the extreme electrodes poses a risk of electrode oxidation but optimized device operation controls this risk by constraining the voltage locally. For the same reason, the device is best adapted for the deionization of moderate to low ionic concentrations, such as river water, well water, or municipal water. In summary, this work provides a simpler yet highly effective way of scaling up CDI for water-cleaning applications.

Long-term implant survival following hemiarthroplasty for fractured neck of femur.

Several different designs of hemiarthroplasty are used to treat intracapsular fractures of the proximal femur, with large variations in costs. No clinical benefit of modular over monoblock designs has been reported in the literature. Long-term data are lacking. The aim of this study was to report the ten-year implant survival of commonly used designs of hemiarthroplasty. Patients recorded by the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) between 1 September 1999 and 31 December 2020 who underwent hemiarthroplasty for the treatment of a hip fracture with the following implants were included: a cemented monoblock Exeter Trauma Stem (ETS), cemented Exeter V40 with a bipolar head, a monoblock Thompsons prosthesis (Cobalt/Chromium or Titanium), and an Exeter V40 with a Unitrax head. Overall and age-defined cumulative revision rates were compared over the ten years following surgery. A total of 41,949 hemiarthroplasties were included. Exeter V40 with a Unitrax head was the most commonly used (n = 20,707, 49.4%). The overall rate of revision was small. A total of 28,201 patients (67.2%) were aged > 80 years. There were no significant differences in revision rates across all designs of hemiarthroplasty in patients of this age at any time. The revision rates for all designs were < 3.5%, three years postoperatively. At subsequent times the ETS and Exeter V40 with a bipolar head performed well in all age groups. The unadjusted ten-year mortality rate for the whole cohort was 82.2%. There was no difference in implant survival between all the designs of hemiarthroplasty in the first three years following surgery, supporting the selection of a cost-effective design of hemiarthroplasty for most patients with an intracapsular fracture of the hip, as determined by local availability and costs. Beyond this, the ETS and Exeter bipolar designs performed well in all age groups.