Thermal Management in Flexible and Foldable Electronics: A Deep Dive into Challenges and Solutions

Flexible and foldable electronics have moved from laboratory curiosities to commercial realities, with products such as the Samsung Galaxy Z Fold series, Huawei Mate X, and various wearable health monitors now on the market. These devices offer unprecedented design freedom, allowing screens to bend, roll, and fold without breaking. However, the transition from rigid to flexible form factors introduces severe thermal management challenges that directly impact performance, battery life, and long-term reliability. Unlike conventional rigid devices, which can rely on thick metal heat sinks, copper vapor chambers, and active fans, flexible electronics require cooling solutions that can deform repeatedly without losing effectiveness. This article explores the fundamental thermal obstacles unique to flexible and foldable systems, the key contributing factors, and the most promising strategies—from novel materials to adaptive architectural approaches—that are being developed to keep these devices cool under pressure.

Understanding Thermal Challenges in Flexible Electronics

The core problem is that flexible substrates—typically polymers such as polyimide (PI), polyethylene terephthalate (PET), or thermoplastic polyurethane (TPU)—have thermal conductivities in the range of 0.1–0.3 W/m·K, compared to copper’s ~400 W/m·K or even silicon’s ~150 W/m·K. This means heat generated by processors, batteries, and display driver ICs cannot spread laterally or vertically as efficiently as in a rigid PCB or metal chassis. The result is pronounced localized hot spots that can exceed safe operating temperatures within seconds of high-load activity, such as gaming, video streaming, or wireless charging.

Further complicating matters, flexible devices undergo repeated mechanical strain. Folding introduces creases that can delaminate thermal interface materials, break brittle thermal vias, or compress air gaps, altering heat pathways unpredictably. The mechanical hinge area in foldable phones is especially problematic: it must allow a 180-degree rotation while maintaining electrical and thermal continuity across the flexible display and the two rigid halves of the device. Any disruption in thermal contact leads to rapid temperature rises, potentially triggering throttling or even permanent damage to the OLED layers or battery cells.

Reliability concerns extend beyond immediate overheating. Accumulated thermal cycling—where the device heats up during use and cools when idle—can cause fatigue in flex cables, solder joints on flexible printed circuits (FPCs), and the adhesive layers that bond the display stack. Over hundreds or thousands of fold cycles, these thermal stresses combine with mechanical bending to accelerate failure. For example, cyclic temperature changes can cause differential expansion between the metallic traces and the polymer substrate, leading to microcracks that increase electrical resistance and generate even more heat in a feedback loop.

Another subtle issue is that thermal management in flexible electronics must contend with the user’s hand. Unlike a laptop that sits on a desk, a foldable phone is often held, and the skin contact acts as a natural heat sink. But passive cooling via the user’s hand is inconsistent; it depends on blood flow, ambient temperature, and how firmly the device is gripped. Designers cannot rely on this uncontrolled variable, so they must build in enough thermal capacity and spreading to keep surface temperatures below the 40–45°C range that becomes uncomfortable for prolonged contact.

To appreciate the magnitude of the challenge, consider that in a typical rigid smartphone, the main processor can draw 5–10 W momentarily, and the body of the phone—with its glass, metal, and large battery—acts as a thermal buffer. In a foldable, the same processor must be confined in a thinner, lighter form factor, often with a smaller battery and less structural mass. The result is a temperature rise that can be 30–50% steeper than in a comparable rigid model, making effective thermal management a critical enabler for the entire product category.

Key Factors That Exacerbate Thermal Management Issues

Material Limitations of Flexible Substrates

As noted, the polymer substrates used in flexible electronics have inherently low thermal conductivity. But it is not just the base substrate—the entire material stack contributes. Transparent conductive layers for touchscreens, such as indium tin oxide (ITO) coated on flexible films, have poor heat spreading. Encapsulation layers that protect OLEDs from moisture and oxygen also tend to be thermal insulators. Even the conductive traces in flexible printed circuits are typically thin copper (9–18 µm) on a polyimide film, which restricts cross-sectional area for heat conduction. To make matters worse, many of these layers are bonded with adhesives that have thermal conductivities below 0.2 W/m·K, creating a series of thermal bottlenecks that dramatically reduce the overall effective conductivity of the device stack.

Device Miniaturization and High Power Density

Foldable and flexible devices pack advanced components—such as high-resolution foldable OLEDs, multiple cameras, 5G modems, and large batteries—into volumes that are often thinner than 7 mm when unfolded. The power density (watts per cubic centimeter) in these devices rivals that of some server processors. For instance, a foldable phone’s main SoC might occupy only a few hundred square millimeters of board area, yet dissipate 8–10 W under peak load. Without effective heat spreading, the junction temperature can hit 100°C in seconds, triggering immediate throttling. The proximity of the processor to the battery exacerbates the problem, as lithium-ion cells degrade faster above 45°C. Thermal management must simultaneously protect the battery, the display, and the user's hand, all within a confined, bending structure.

Mechanical Deformation and Dynamic Heat Paths

Perhaps the most unique thermal challenge in flexible/foldable electronics is that the heat flow architecture changes every time the device is folded or unfolded. When open, the device may have two separate heat spreaders bridged by a flexible thermal tape or a sliding thermal connector. When closed, those two halves are stacked, and heat from the processor in one half can conduct through the hinge to the opposite half, but the contact resistance at the hinge interface can vary dramatically depending on the fold angle and wear over time. This dynamic thermal impedance means that traditional steady-state thermal simulations are insufficient; engineers must model hundreds or thousands of mechanical states to ensure safe temperatures under all use conditions. Moreover, the crease area of the display—a region that is repeatedly bent to a radius as tight as 2–3 mm—experiences elevated mechanical stress that can reduce the thermal contact between layers, leading to a hot spot that grows with each fold cycle.

Environmental and Use-Case Variability

Flexible electronics are found in wearables that must operate in a wide range of environments—from hot summer days (45°C) to cold winter conditions (-20°C). The thermal design must account for these extremes, but the low thermal mass of plastic substrates means that the device temperature can swing rapidly with ambient conditions. In a cold environment, a flexible device may heat up quickly under load, but the low thermal conductivity prevents the heat from spreading to the casing, so the user feels a hot spot while the rest of the device remains cold. This uneven distribution can also cause condensation within the device, risking short circuits. In hot environments, the lack of effective cooling forces aggressive throttling, diminishing user experience. The challenge is to create a thermal system that adapts to both environmental and mechanical variations without adding bulk or rigidity.

Strategies for Effective Thermal Management in Flexible and Foldable Devices

Researchers and engineers have proposed a wide array of solutions, ranging from advanced materials with engineered thermal properties to dynamic architectural designs that reconfigure heat paths. The most promising approaches can be grouped into four categories: materials innovation, design optimization, active cooling, and system-level thermal management.

Advanced Thermally Conductive Materials

The first line of defense is to replace or augment the low-conductivity materials with alternatives that offer both flexibility and high thermal transport. Two-dimensional materials such as graphene and boron nitride (h-BN) have emerged as leading candidates. Graphene films can achieve thermal conductivities of 2000–5000 W/m·K in the planar direction, while remaining mechanically flexible and lightweight. Companies like XG Sciences and Graphenea now supply graphene-based thermal films that can be laminated onto flexible circuits or displays. These films can be produced as free-standing sheets as thin as 10 µm and can withstand repeated bending to radii below 1 mm without significant degradation in thermal performance. Similarly, vertically aligned carbon nanotube (CNT) arrays can serve as thermal interface materials with conductivities ~10–50 W/m·K in the through-plane direction, ideal for bridging the gap between a hot chip and a heat spreader.

Another material class uses silver nanowires (AgNWs) embedded in a polymer matrix. These composites can achieve thermal conductivities of 30–100 W/m·K while remaining flexible and transparent—a critical requirement for touch-sensitive display layers. Researchers have also developed liquid metal (e.g., gallium-indium alloys) embedded in soft elastomers to create stretchable thermal conductors that can handle the bending and folding without cracking. However, these liquid metal composites must be carefully encapsulated to prevent leakage.

For the substrate itself, composites that combine a flexible polymer with a high-conductivity filler (such as carbon fiber, graphite flakes, or ceramic particles) offer a promising middle ground. For example, a polyimide substrate loaded with 30% volume fraction of boron nitride nanosheets can achieve a thermal conductivity of ~1.5 W/m·K—an order of magnitude better than pure PI—while retaining enough flexibility to be folded over 200,000 times. Such composite substrates are now entering commercial production for flexible PCB applications.

Design Optimization: Thermal Vias, Heat Spreaders, and Anisotropic Films

Beyond materials, clever geometric design can significantly improve heat dissipation. One approach is the use of flexible thermal vias—conductive pillars that go through the thickness of a flexible substrate to transfer heat from a hot component on one side to a copper plane on the opposite side. These vias can be made from copper-filled or solder-filled cylindrical holes, similar to those in rigid PCBs, but they must be designed to withstand bending. By placing arrays of small-diameter vias (e.g., 0.1 mm diameter with a pitch of 0.5 mm) in the region under the processor, engineers can effectively reduce the thermal resistance through the substrate by up to 50%. The challenge is that repeated folding can cause stress concentration around these vias, leading to cracks. Advanced design uses staggered patterns and flexible epoxy fillers to mitigate this.

Microchannel heat spreaders are another innovative design. Instead of a solid metal heat sink, a thin polymer layer with embedded microchannels (width ~50 µm) is filled with a thermally conductive fluid such as water or a dielectric coolant. When the device is used, capillary forces or a small piezoelectric pump circulate the fluid, carrying heat away from hot spots to a remote area where it can dissipate through the casing. These microfluidic coolers can be as thin as 200 µm and can be fabricated on flexible films that bend with the device. Researchers at the University of Illinois have demonstrated flexible microfluidic cooling systems that maintain uniform temperatures even under heavy bending, offering a potential solution for high-power foldable devices.

Thermal anisotropy—directing heat preferentially along one direction—can also be exploited. Anisotropic pyrolytic graphite sheets (PGS) have in-plane thermal conductivities up to 1500 W/m·K but through-plane values of only 10 W/m·K. By placing these sheets with their high-conductivity plane aligned with the main heat spreading direction (e.g., from processor to the hinge area), designers can channel heat efficiently along the device while minimizing unwanted transfer to the battery or display. Multiple layers of PGS can be laminated with interlaced orientations to create a 2D heat spreader that is thin, flexible, and effective.

Active Cooling Techniques for Flexible Systems

While passive solutions are preferred for their simplicity and reliability, some flexible devices—particularly those housing powerful processors or wireless charging coils—may require active cooling. Traditional fans are too bulky, but solid-state cooling technologies are being miniaturized for flexible integration. Electrocaloric and thermoelectric coolers (TECs) can be built on flexible substrates. A flexible thermoelectric module made from p- and n-type bismuth telluride legs on a polyimide substrate can provide localized cooling of 5–10°C, drawing only a few hundred milliwatts. These modules can be placed directly over the hottest components and activated only when needed, such as during intensive gaming sessions. The heat rejected from the cold side is then spread across the device by a flexible graphite sheet.

Another emerging active technique uses phase change materials (PCMs) that absorb heat when they melt. For example, paraffin wax or fatty acids with melting points around 40–45°C can be encapsulated in a flexible pouch and placed over a processor. During a burst of high power, the PCM absorbs the latent heat of fusion (typically 150–250 J/g), preventing the temperature from rising above the melting point for a limited time (e.g., 5–10 minutes). After the load subsides, the PCM solidifies and releases the stored heat gradually. This approach is particularly well-suited for the thermal spikes common in mobile devices, where peak loads are short-lived. PCM-filled polymer composites that are soft and bendable are now being developed for thin, flexible electronics like smartwatches and foldable phones.

System-Level Thermal Management and Adaptive Architectures

Finally, thermal management in flexible electronics must be considered at the system level—from the chip to the user's hand. This includes dynamic power management software that adjusts clock speeds and voltages based on real-time temperature sensor readings placed at multiple points on the flexible circuit. Advanced machine learning algorithms can predict hot spot formation based on user behavior (e.g., fold angle, grip, app usage) and proactively adjust thermal and power parameters. For instance, a foldable phone might reduce the processor frequency by 20% just before the user unfolds it, anticipating a shift in thermal contact resistance that could cause an abrupt temperature spike.

The hinge itself can be engineered as a thermal bridge. Some foldable phones now use a multi-link hinge that incorporates thermal pads or sliding copper foil strips that maintain contact between the two halves in both open and closed positions. This design helps equalize temperatures across the entire device, using the larger surface area of the battery and the opposite half as a heat sink. Additionally, the hinge area can be designed with a slight gap to allow for airflow—even natural convection can provide some cooling if the gap is oriented appropriately. Since the device is often used with the hinge partially open (e.g., the tent mode for hands-free video), designers can optimize the hinge’s shape to create a chimney effect that draws cool air in and expels warm air.

Another system-level approach is to use the metal structural components—such as the midframe or hinge brackets—as thermal conduits, even if they must be segmented for flexibility. Segmented aluminum plates connected by thin flexible copper braids can allow the metal structure to bend while providing low-resistance heat paths. These braids, or "thermal flexi-joints," are essentially bundles of fine copper wires that can twist and stretch, transmitting heat across a hinge or fold region with a thermal resistance of roughly 0.5–1°C/W—far lower than relying on the polymer substrate alone.

Future Outlook: Toward Truly Seamless Thermal Management

The pace of innovation in flexible electronics thermal management is accelerating, driven by both academic research and industry competition. We can expect several developments in the next few years that will bring foldable and flexible devices closer to the thermal performance of their rigid counterparts.

Next-Generation Materials and Manufacturing

One promising direction is the integration of highly oriented pyrolytic graphite (HOPG) films with sub-micrometer thicknesses that can be printed or laminated in mass production. Better control over the crystalline alignment of graphene films during chemical vapor deposition (CVD) will yield even higher in-plane thermal conductivities. We may also see the emergence of "self-healing" thermal interface materials that contain microcapsules of thermally conductive filler that release when a crack forms, reestablishing the thermal path. Such materials could dramatically extend the lifetime of flexible devices.

Thermal Design Automation

As flexible devices become more complex, thermal simulation tools that account for mechanical bending and dynamic boundary conditions will become standard. Emerging software platforms like Ansys Icepak and COMSOL Multiphysics already allow engineers to couple thermal, mechanical, and electrical simulations to predict hot spots under various folding scenarios. In the future, these tools could be integrated with design automation algorithms that optimize the placement of thermal vias, heat spreaders, and active cooling elements based on the expected usage patterns and fold cycles. This would reduce the need for costly physical prototypes and enable faster iteration of thermal management solutions.

Integration with Energy Harvesting and Wireless Charging

A fascinating frontier is the convergence of thermal management with energy harvesting. The waste heat from a flexible device could be partially recovered by thin-film thermoelectric generators (TEGs) that convert temperature gradients into electricity. A flexible TEG placed between a hot processor and the relatively cooler display could generate enough power to run a sensor or extend battery life by a few percent. Though the efficiency is currently low (~1–2%), ongoing research into organic thermoelectric materials and printed manufacturing could make this viable for low-power wearables.

Industry Standards and Reliability Testing

Consumer trust in foldable devices hinges on durability. As thermal management solutions evolve, industry-wide standards for testing thermal performance under bending cycles (e.g., IEC 60068-2-42 for thermal cycling) must be adapted to include mechanical loading. The JEDEC solid-state technology association is currently working on a standard for thermal characterization of flexible semiconductor packages. Such standards will help manufacturers compare thermal solutions and ensure that devices can withstand the combined thermal and mechanical stresses of daily use.

Conclusion: Thermal Management as a Key Enabler

Flexible and foldable electronics are not merely a passing trend; they represent a fundamental shift in how we design and interact with electronic devices. However, this shift cannot succeed without solving the thermal management puzzle. The combination of low-conductivity substrates, high power densities, dynamic mechanical states, and user comfort constraints creates a uniquely challenging problem. Fortunately, the materials, design approaches, and active cooling techniques outlined in this article offer a viable path forward. From graphene films and microfluidic loops to adaptive software and segmented metal heat paths, the toolbox for thermal management in flexible devices is expanding rapidly. Companies that invest in these solutions today will be best positioned to deliver the reliable, high-performance foldable and flexible devices that consumers will demand tomorrow. For further reading on advanced thermal materials and flexible electronics, consult the review by Moore et al. on thermal management of flexible systems published in Advanced Materials Technologies, and the industry report by IDTechEx on thermal management for flexible electronics 2023–2033. Additionally, practical examples of graphene-based heat spreaders are documented in Graphene Info, and the latest foldable phone thermal design innovations are discussed in iFixit’s teardown of the Galaxy Z Fold 3.