A review of lightweight bionic sandwich and additive structural designs for hydrogen fuel cell bipolar plates

1 Fundamental challenges and design criteria for lightweight bipolar plates

The bipolar plate represents one of the most critical components in proton exchange membrane fuel cells, serving multiple essential functions including electrical conduction between adjacent cells, reactant gas distribution, heat removal, and structural support for the membrane electrode assembly (MEA) (Bong et al., 2017). Despite their functional importance, bipolar plates contribute disproportionately to the overall stack mass, accounting for approximately 60%–80% of the total weight and 30%–45% of the total cost of PEMFC systems (Huang et al., 2023). This substantial weight penalty poses significant barriers to the widespread commercialization of fuel cell technology, particularly for weight-sensitive applications such as automotive propulsion, unmanned aerial vehicles (UAVs), and portable electronic devices (Choi et al., 2012).

Previous reviews have addressed various aspects of bipolar plate technology, including materials and manufacturing methods (Hermann et al., 2005; Leng et al., 2020), flow-field design (Li and Sabir, 2005), composite materials (Li et al., 2024; Mishra et al., 2024), and additive manufacturing applications (Baroutaji et al., 2024). However, these reviews predominantly treat lightweight structural design, bionic-inspired architectures, topology optimization, and additive manufacturing as separate topics, without examining their synergistic integration for bipolar plate applications. Specifically, the convergence of bionic sandwich structures—inspired by natural cellular architectures—and topology-optimized lattice configurations realized through additive manufacturing remains largely unexplored in the existing review literature (Hu et al., 2014).

This review addresses this gap by providing a comprehensive examination of the integration between bionic-inspired sandwich structures, topology optimization, and additive manufacturing technologies specifically for lightweight bipolar plate applications. Unlike previous reviews that treat these domains in isolation, the present work adopts an integrative perspective, analyzing how bio-inspired design principles can be realized through advanced computational optimization and additive manufacturing to simultaneously address mechanical, electrical, and fluidic requirements (Jin et al., 2014). Comprehensive comparison of lightweight bipolar plate design strategies as Table 1. The discussion encompasses five interconnected domains: (1) the fundamental challenges and design criteria for lightweight bipolar plates in PEMFC applications; (2) bionic-inspired sandwich structures, including honeycomb and corrugated configurations derived from natural biological structures; (3) topology optimization and lattice-based lightweight designs enabled by advanced computational methods; (4) additive manufacturing technologies, particularly laser powder bed fusion (LPBF) and selective laser melting (SLM) for metallic bipolar plate fabrication; and (5) composite material strategies and hybrid structural approaches for achieving optimal weight-to-performance ratios. Through systematic analysis of recent literature, this review identifies that bio-inspired vertical honeycomb sandwich (BVHS) structures fabricated via LPBF can achieve specific energy absorption improvements of 56.99% and specific bending strength enhancements of 46.91% compared to conventional configurations. Furthermore, additive manufacturing enables the realization of complex three-dimensional flow fields that enhance reactant distribution uniformity and water management capabilities (Kermani, 2022). The integration of bionic design principles with additive manufacturing technologies offers promising pathways for developing next-generation lightweight bipolar plates that satisfy the stringent requirements of automotive, aerospace, and portable power applications (Kim and Bong, 2015).

TABLE 1. Comprehensive comparison of lightweight bipolar plate design strategies.

The development of lightweight bipolar plate solutions has become a research priority aligned with the U.S. Department of Energy (DOE) technical targets, which specify stringent requirements for electrical conductivity (>100 S/cm), mechanical strength (>25 MPa flexural strength), corrosion resistance (<1 μA/cm²), and gas permeability (<2 × 10⁻⁶ cm³/(cm²·s)) (Leng et al., 2020). Traditional bipolar plate materials include graphite, metallic alloys, and polymer composites, each presenting distinct trade-offs between weight, performance, and manufacturability. Graphite plates offer excellent corrosion resistance and electrical conductivity but suffer from brittleness, requiring thicknesses of several millimeters that contribute to excessive stack volume and weight (Nikam and Reddy, 2006). Metallic bipolar plates, typically fabricated from stainless steel, aluminum, or titanium alloys, provide superior mechanical strength and can be manufactured with thinner cross-sections, but face challenges related to corrosion in the acidic fuel cell environment and the need for protective coatings (Alo et al., 2019). Composite materials combining conductive fillers with polymer matrices offer intermediate solutions, though their relatively low electrical conductivity and complex processing requirements have limited widespread adoption. The fundamental challenge in lightweight bipolar plate design lies in achieving the optimal compromise between weight reduction and the maintenance of essential functional properties, necessitating innovative structural configurations and advanced manufacturing approaches (Koo and Park, 2012). Figure 1 presents a comprehensive visual overview of the state-of-the-art lightweight bionic sandwich and additive structural designs for hydrogen fuel cell bipolar plates, systematically organized into six interconnected panels.

Literature Search Strategy. This review was conducted through systematic searches of Web of Science, Scopus, ScienceDirect, and Google Scholar using keywords including “bipolar plate”, “lightweight design”, “bionic structure”, “topology optimization”, “lattice structure”, “additive manufacturing”, “selective laser melting”, and “PEMFC”. The search covered peer-reviewed English-language publications from 2005 to 2024. Inclusion criteria focused on studies reporting lightweight structural designs, quantitative performance metrics, and sufficient methodological detail for comparative analysis. Studies exclusively addressing non-bipolar-plate components, non-PEMFC applications, or lacking experimental/numerical validation were excluded (Koç and Mahabunphachai, 2007). The screening process followed PRISMA guidelines, yielding 47 primary references for detailed analysis, supplemented by seminal works identified through citation tracking (Lee and Lim, 2005).

2 Bionic-inspired sandwich structures for lightweight bipolar plates

Nature has evolved numerous efficient structural configurations that maximize strength-to-weight ratios through optimized material distribution and geometric organization. The application of bionic design principles to bipolar plate structures has emerged as a promising strategy for achieving significant weight reductions while preserving mechanical integrity and functional performance (Mahabunphachai and Koç, 2008). Honeycomb sandwich structures, inspired by the cellular architectures found in insect elytra and plant stems, represent one of the most extensively investigated bionic configurations for lightweight bipolar plates (Chen et al., 2024). These structures consist of thin face sheets separated by a cellular core, providing high specific stiffness and energy absorption capacity through the efficient distribution of material in load-bearing regions (Nefedkin et al., 2021). Recent research has demonstrated that bio-inspired vertical honeycomb sandwich (BVHS) structures, designed based on the microstructural features of Cybister beetle elytra, exhibit superior performance characteristics compared to conventional vertical honeycomb sandwich (CVHS) configurations. The introduction of fractal thin walls in BVHS designs enables self-supporting characteristics during fabrication and improves formability, resulting in specific energy absorption (SEA) improvements of 56.99% and specific bending strength enhancements of 46.91% relative to conventional structures (Chen et al., 2024). Finite element analysis has revealed that the fractal geometric features effectively redistribute stresses during bending deformation, while the cellular core topology influences current density distribution and electrical conductivity properties. Corrugated sheet structures represent another bionic-inspired approach, mimicking the undulating morphologies observed in natural membranes and shells (Peng et al., 2008). Corrugated bipolar plates can be fabricated through continuous roll forming processes, offering advantages in terms of reduced material thinning and enhanced channel depth compared to conventional stamping methods (Zhang et al., 2019). The corrugated configuration provides increased structural rigidity in the through-thickness direction while maintaining flexibility in the planar directions, facilitating stack assembly and contact pressure distribution. Furthermore, corrugated mesh flow channels have demonstrated effectiveness in reducing flooding and mass transport resistance in gas diffusion layer-less fuel cell configurations (Tanaka and Shudo, 2014). The bionic design paradigm extends beyond specific geometric configurations to encompass topological optimization strategies that mimic the adaptive material distribution observed in biological load-bearing structures. These approaches leverage computational algorithms to identify optimal material layouts that maximize performance metrics while minimizing weight, resulting in organic, non-intuitive geometries that challenge conventional manufacturing constraints. While bionic sandwich structures demonstrate promising specific mechanical properties, several trade-offs warrant consideration. BVHS structures achieve 56.99% improvement in specific energy absorption (Chen et al., 2024), but their fractal thin-wall features introduce manufacturing complexity that may not translate to scalable production. Corrugated configurations offer established roll-forming manufacturability (Zhang et al., 2019) but exhibit lower energy absorption than honeycomb cores. This represents a fundamental trade-off between manufacturing scalability and mechanical performance that remains unquantified. Notably, most studies evaluate mechanical properties in isolation, without integrated electrochemical validation under realistic fuel cell operating conditions (Qiu et al., 2018).

3 Topology optimization and lattice-based lightweight designs

Topology optimization has emerged as a powerful computational methodology for designing lightweight structures with optimized material distribution, enabling the creation of complex geometries that maximize specific performance metrics while minimizing mass. In the context of bipolar plate design, topology optimization algorithms have been applied to identify optimal flow field configurations, structural reinforcement patterns, and material density distributions that enhance the compromise between weight reduction and functional requirements (Guo et al., 2014). The application of topology optimization to gas channel design has demonstrated potential for improving reactant distribution uniformity and reducing pressure drop penalties, with optimized configurations exhibiting performance advantages over conventional serpentine and parallel flow field patterns (Fan et al., 2022). Lattice structures, characterized by periodic or stochastic arrangements of strut elements, represent a specific class of lightweight configurations enabled by topology optimization and additive manufacturing technologies (Smith et al., 2014). These structures offer exceptional specific mechanical properties, with the ability to tailor stiffness, strength, and energy absorption characteristics through controlled variations in lattice topology, relative density, and strut geometry (Wang et al., 2019). For bipolar plate applications, lattice-based sandwich cores provide opportunities for integrating functional features such as flow distribution channels, heat transfer pathways, and structural reinforcement within a unified lightweight framework. The design of lattice structures for bipolar plates must consider the coupled requirements of mechanical load-bearing, electrical conduction, and fluid transport, necessitating multi-objective optimization approaches that balance competing performance criteria (Kermani, 2021). Body-centered cubic (BCC), face-centered cubic (FCC), and octet truss lattice topologies have been investigated for sandwich core applications, with each configuration offering distinct advantages in terms of isotropic stiffness, energy absorption efficiency, and manufacturability. The straight rod sandwich structure has demonstrated particularly promising characteristics, exhibiting optimal formability, the highest specific bending strength (51.93 MPa/g), and the lowest electrical resistance (2.82 mΩ) among investigated lattice configurations (Chen et al., 2024). Variable rod diameter designs, informed by current density distribution simulations, have achieved specific power density improvements of 23.23% compared to traditional solid bipolar plates, while realizing weight reductions of 29.63%. These results demonstrate the potential for topology-optimized lattice structures to simultaneously address the mechanical, electrical, and fluidic requirements of bipolar plate applications while achieving substantial weight savings. Topology-optimized lattice designs face practical challenges in balancing competing requirements. The straight rod structure achieves the highest specific bending strength and lowest electrical resistance (Chen et al., 2024), yet the variable rod diameter design—while improving power density by 23.23%—introduces manufacturing complexity that may compromise repeatability. Kermani (2021) suggested that functionally graded porous materials may outperform uniform lattices in reactant distribution, but this direction remains largely unexplored. A critical limitation is the reliance on simplified models that inadequately represent coupled structural-electrochemical-fluidic interactions and AM manufacturability constraints.

4 Additive manufacturing technologies for metallic bipolar plates

Additive manufacturing (AM) technologies have revolutionized the fabrication of complex metallic components, offering unprecedented design freedom for realizing optimized geometries that are infeasible through conventional manufacturing methods. Laser powder bed fusion (LPBF), also known as selective laser melting (SLM), has emerged as the predominant AM technology for metallic bipolar plate fabrication, enabling the production of intricate internal structures, optimized flow fields, and lightweight lattice configurations with high dimensional accuracy (Baroutaji et al., 2024). The LPBF process involves the selective melting of fine metal powder layers using a focused laser beam, building components layer-by-layer from three-dimensional digital models. This approach offers several advantages for bipolar plate manufacturing, including the ability to fabricate complex three-dimensional flow fields with enhanced reactant distribution and water management capabilities, the integration of internal cooling channels and structural features, and the elimination of assembly steps through monolithic fabrication (Yang et al., 2017). Experimental investigations have demonstrated that SLM-fabricated 316 L stainless steel bipolar plates achieve high forming quality with dimensional errors less than 4%, and exhibit performance characteristics comparable or superior to conventionally machined plates (Huang et al., 2022). The square mesh flow field (SMFF) design fabricated via SLM achieved power densities of 387.9 mW/cm² at 0.3 V, representing approximately 30% improvement over obstruction mesh flow field configurations. The enhanced performance is attributed to more uniform gas and water distribution, reduced ohmic losses, and improved electrical conductivity (Huang et al., 2022). Three-dimensional flow field bipolar plates with controlled porosity fabricated through SLM have demonstrated maximum power densities of 0.547 W/cm², representing 8.96% improvements over conventional two-dimensional serpentine designs (Huang et al., 2023). The superior performance of 3D flow fields results from enhanced mass transfer, improved heat dissipation, and optimized water management capabilities. Despite these advantages, LPBF fabrication of bipolar plates faces several challenges, including high production costs, limited build rates, surface roughness requirements, and the need for post-processing treatments to achieve adequate corrosion resistance and electrical conductivity (Dawson et al., 2015). The development of process-parameter optimization strategies, novel powder compositions, and hybrid manufacturing approaches combining additive and subtractive processes represents active research directions for addressing these limitations. The development of multilayered composite structures, functionally graded materials, and integrated MEA-BP assemblies represents emerging directions for achieving further weight reductions and performance enhancements. The convergence of advanced materials, bionic design principles, and additive manufacturing technologies offers unprecedented opportunities for developing next-generation bipolar plates that satisfy the stringent requirements of commercial fuel cell applications while achieving substantial weight savings.

Despite performance advantages, AM bipolar plates face significant barriers to commercialization. LPBF achieves dimensional errors below 4% (Huang et al., 2022), but production costs and limited build rates remain incompatible with high-volume manufacturing. Post-processing (surface polishing, coating, heat treatment) is often mandatory, further increasing costs (Dawson et al., 2015). The optimal surface roughness threshold remains debated, and—critically—long-term durability data under realistic operating conditions are largely absent. Scalability from single-cell prototypes to full-stack production has not been demonstrated.

5 Composite material strategies and hybrid structural approaches

Composite materials offer alternative pathways for achieving lightweight bipolar plate configurations through the combination of conductive fillers with lightweight polymer matrices. Carbon fiber reinforced polymer (CFRP) composites have emerged as particularly promising candidates, exhibiting high specific strength and stiffness that enable significant weight reductions compared to conventional graphite and metallic plates (Leng et al., 2020). Non-woven carbon felt based composites have attracted attention due to their requirement for lower curing pressures compared to unidirectional carbon fiber or fabric composites, facilitating manufacturing scalability and cost reduction. The integration of cathode and anode functionalities into a single composite bipolar plate has demonstrated potential for reducing stack thickness and weight while maintaining electrical performance through the soft layer method, which exposes bare carbon fibers on the composite surface to minimize contact resistance (Leng et al., 2020). Expanded graphite based composites represent another lightweight solution, offering the advantages of low density, good corrosion resistance, and high electrical conductivity while avoiding the brittleness limitations of pure graphite plates (Nikam and Reddy, 2006). The porous and sandwich structure characteristics of expanded graphite plates provide flexibility and impact resistance benefits, with manufacturing costs significantly lower than conventional graphite machining approaches. Hybrid structural approaches combining multiple material systems and manufacturing methods have demonstrated potential for achieving optimal performance compromises. Carbon fiber plate reinforced with polymeric resin, fabricated with thicknesses as low as 170 μm and coated with conductive carbon layers, has achieved weight reductions of 85.4% and 76.4% compared to conventional graphite and metallic bipolar plates, respectively, while satisfying DOE targets for electrical conductivity, mechanical strength, and gas permeability (Chen et al., 2024). Metal-polymer hybrid configurations, incorporating thin metal foils or coatings on polymer substrates, leverage the conductivity of metals while minimizing weight through reduced metal content. Advanced coating technologies such as physical vapor deposition enable uniform metal layers as thin as 5–10 μm, providing sufficient conductivity while contributing minimally to overall weight (Baroutaji et al., 2024). The development of multilayered composite structures, functionally graded materials, and integrated MEA-BP assemblies represents emerging directions for achieving further weight reductions and performance enhancements. The convergence of advanced materials, bionic design principles, and additive manufacturing technologies offers unprecedented opportunities for developing next-generation bipolar plates that satisfy the stringent requirements of commercial fuel cell applications while achieving substantial weight savings.

Composite strategies present distinct trade-offs. Carbon fiber plates achieve 85.4% weight reduction (Chen et al., 2024) but rely on CVD with scalability concerns. Metal-polymer hybrids minimize weight yet introduce interface reliability challenges—thermal expansion mismatch and galvanic corrosion remain insufficiently investigated. Expanded graphite offers low density but requires thicker configurations, offsetting weight advantages. Standardized testing protocols are notably absent.

An emerging direction that may transcend these trade-offs is multifunctional integration. Zhang et al. (2023) demonstrated an integrated porous BP–GDL structure eliminating the conventional GDL, using metal foam as simultaneous flow field, current collector, and gas diffusion medium. This reduces mass transfer resistance and cell thickness while enhancing power density—addressing lightweighting through functional integration rather than material substitution.

The strategies reviewed here complement this approach. Bionic sandwich cores can be designed with gradient porosity to merge structural support and gas diffusion. Topology-optimized lattices can spatially tailor permeability and conductivity, outperforming uniform foams. Additive manufacturing enables monolithic graded structures combining flow field, current collection, and diffusion in one component.

Yet this convergence introduces new challenges. Integrated structures sacrifice mechanical robustness, raising concerns about clamping pressure and dimensional stability. Corrosion protection of porous internal surfaces is complicated by intricate geometries. Unified qualification criteria—merging traditional BP and GDL metrics—remain undeveloped.

Hybrid architectures combining a lightweight sandwich frame with an integrated porous core may offer the optimal compromise, leveraging face-sheet stiffness for mechanical stability while the graded core assumes transport functions. Realizing this vision requires coupled structural-electrochemical optimization frameworks that remain largely unexplored.

6 Conclusions and future perspectives

This review has examined the state-of-the-art in lightweight bionic sandwich and additive structural designs for hydrogen fuel cell bipolar plates. Bio-inspired vertical honeycomb sandwich structures fabricated via LPBF achieve specific energy absorption improvements of 56.99% and specific bending strength enhancements of 46.91% compared to conventional configurations, while topology-optimized lattice designs enable weight reductions of 29.63% alongside specific power density improvements of 23.23%. Additive manufacturing facilitates complex three-dimensional flow fields that enhance mass transfer and water management, and composite approaches offer alternative pathways with carbon fiber plates achieving 85.4% weight reduction relative to conventional graphite.

Critical limitations nevertheless constrain near-term commercialization. Manufacturing costs for LPBF-fabricated components remain prohibitive for automotive-scale production, with build rates incompatible with high-volume throughput requirements. The corrosion susceptibility of high-surface-area lattice structures and the coating challenges associated with complex internal geometries have not been adequately resolved, and long-term durability data exceeding 5,000 h under realistic operating conditions are absent for most lightweight configurations. Quality control methodologies for additively manufactured and composite bipolar plates remain underdeveloped, with limited in-situ monitoring capabilities and absent standardized testing protocols. Industrial implementation barriers—including compression molding cycle times, CVD coating throughput limitations, and supply chain integration—have received insufficient attention in academic research.

Addressing these challenges requires a multifaceted research agenda. Cost reduction and scalability must be pursued through hybrid manufacturing approaches combining additive and subtractive processes, high-speed sintering technologies, and continuous composite molding methods capable of bridging the gap between laboratory prototypes and industrial production. Concurrently, systematic long-term durability validation exceeding 5,000 h under realistic drive-cycle conditions—including thermal cycling, start-stop protocols, and contamination scenarios—is urgently needed across metallic, composite, and hybrid lightweight configurations. Novel corrosion protection strategies capable of uniformly coating intricate internal surfaces of lattice and cellular structures must be developed, accompanied by accelerated testing protocols tailored to high-surface-area architectures. Quality control and standardization efforts should focus on in-situ process monitoring, predictive defect detection, and unified qualification criteria that merge traditional bipolar plate and gas diffusion layer performance metrics. Finally, the convergence of lightweight structural strategies with emerging integrated bipolar plate–gas diffusion layer architectures represents a particularly promising frontier, requiring the development of coupled structural-electrochemical optimization frameworks that remain largely unexplored.

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Footnotes

Edited by: Josep Gomez-Soriano, Universitat Politècnica de València, Spain

Reviewed by: Christian Spreafico, University of Bergamo, Italy