Flexible electronics (or foldable electronics) are currently in high demand due to the need for device miniaturization and interoperability in a host range of applications, including wearable electronics, smart textiles, foldable smartphones, and implantable sensors. 

Recently, foldable electronics have taken off with the concept of foldable phones. Image used courtesy of Samsung Newsroom

However, these devices experience particular challenges, such as low power conversion efficiency, mechanical instability, physical durability, and complex and expensive fabrication processes. This article explores the latest trends in foldable electronics, limitations, and leading solutions.

Better Processes = Better Flexible Electronics 

To begin with, let's dive into the latest innovations in foldable electronics. Two key players in both research and commercial fields, respectively, are Stanford and Samsung.  

Researchers at Stanford proposed a new method for manufacturing 2D ultra-thin flexible electronics. Unlike conventional methods that require high-temperature fabrication, which sometimes adversely impact the overall solution, their approach involves growing layers of MoS2 atoms, at intervals, on glass-coated silicon blocks. With that process, the researchers created a 5-micron thick flexible electronics substrate that can integrate into several devices and real-world applications with additional processing. 

Similarly, Samsung's recent publication explores how its team utilized a new manufacturing process with existing semiconductor processes to create an industry-leading flexible wearable device. The device offers real-time heart rate monitoring by incorporating a photoplethysmography sensor and expandable organic light-emitting diode (OLED) display into a single unit device. 

OLED vs. microLEDs. Image used courtesy of Eyerys

Samsung also reported that the device could maintain a high performance after undergoing 30% deformation and more than 1000 times stretchability, demonstrating mass applicability of the manufacturing process. 

To achieve higher performance, quality, flexibility, and durability in foldable displays, the team replaced active-matrix organic LEDs (AMOLED) with microLEDs (µLEDs). The researchers noted that µLED-integrated foldable displays could offer critical benefits over similar AMOLED displays since µLED technology could provide higher efficiency, high dynamic range (HDR), ambient constant ratio (ACR), luminance output, and faster response time than AMOLED.

With Stanford's flexible manufacturing technique and Samsung's attempt at mass-producing flexible wearable devices, the technology has the opportunity to experience a smooth transition from the research and development (R&D) phase to the full-scale commercialization.

Now that two recent innovations in manufacturing foldable electronics, let's take a look at the key players working within this trending technology.

Foldable Phones and Electronics: Key Players 

With recent innovations in pushing foldable tech to a more mainstream level, two key players are LG Chem and Samsung. 

Despite moving out of the phone industry, LG Chem recently developed a foldable display material to mark an entrance into the next-gen materials market. The company claimed that while this material exhibits the strength of glass, it retains the flexibility of plastic. This cover window, which the company calls "Real Folding Window," promises adequate protection for foldable IT devices. 

LG Chem's ultra-thin solution states to offer greater heat resistance, mechanical stability, durability, and transmittance, solving fold-related issues in flexible electronics. The company made significant improvements to conventional polyimide film-integrated electronics by ensuring its solution maintains its high performance and durability after folding over 200,000 times at a competitive price. 

LG Chem hopes to develop strong partnerships with industry leaders to incorporate its solution into foldable applications such as smartphones, tablets, and laptops.

The "Real Folding Window" from LG Chem. Image used courtesy of LG Chem

As for Samsung, it has been increasingly incorporating flexibility into recent products, such as the SAIT Proto System and the Samsung Galaxy Z Fold 3. In both products, Samsung's solution aims to provide high performance, efficiency, and flexibility. 

Samsung advanced institute of technology (SAIT) prototype system. Image used courtesy of Samsung

With over ten years of research and continuous development, engineers at Samsung have been mass-producing Samsung foldable smartphones for full-scale commercialization. They incorporate its Eco2 OLEDTM technology into this device, resulting in a 33% higher transmittance rate and 25% lower power consumption rate. 

In collaboration with a host of engineers from different backgrounds, the company hopes to stabilize the capabilities of this innovation and develop novel technologies that could aid the widespread adoption of foldable phones and electronics into the mainstream. However, before this type of technology can fully become mainstream and common technology, it has various hurdles to overcome, which companies are hoping to find solutions for. 

Design Challenges and Latest Solutions

All in all, many different factors limit the design and creation of foldable electronics. 

• Some challenges include:
• mechanical stability
• physical durability
• interfacial adhesion
• power efficiency 
• fabrication processes

Above all other challenges, developing high-performance foldable electronics requires engineers to utilize materials with high mechanical stability during bends and folds. Thus, the engineers cannot incorporate standard metallic electrodes with exceptional electrical properties into their design because of their rigidity and brittleness. In addition to mechanical stability, engineers must consider materials with high flexibility, physical durability, and power efficiency. 

Since most electronic devices comprise component layers (electrodes, semiconductors, and substrates), constant folding and unfolding can adversely affect the adhesion at the interfaces. This wear and tear issue obviously results in damage to the device or component and lowers the product's longevity. 

Thus, engineers also face the challenge of ensuring device durability under extreme strain conditions. Moreover, existing foldable electronics fabrication processes are expensive and complex, limiting mass production, which is a determining factor of why foldable phones are just now attempting to breach the market.

Researchers and industry players are exploring different approaches to address common challenges to widespread adoption and commercialization. 

As mentioned, Samsung is proposing a solution to engineering challenges faced during the design of foldable electronics. This strategy includes incorporating physical stretchability into all materials and elements of the foldable electronics, including the substrate, thin-film transistor, sensor, electrodes, and emission material layer, while maintaining their electrical properties. 

Similarly, another approach from a research paper from Kim et al. proposed developing a polymer thin-film transistor (PTFT) foldable electronics solution that is mechanically stable with adequate interfacial adhesion. The researchers achieved this by switching from heterojunction-based PTFTs to homojunction-based ones, consequently reporting a significant improvement to the resulting foldable electronics. 

In addition, as stated previously, replacing AMOLED technology with the novel µLED one promises several benefits to foldable electronics design.

Though many solutions are starting to appear, could this trend finally make its breakout a marketable, widely commercialized technology?

Keeping the Trend Flexible

Like other novel technologies in the development phase, foldable electronics fabrication still faces technical challenges. However, with continuous research and development, including ample investment, the technology has the potential to evolve from the development phase to mass production and full-scale adoption. 

For the most part, this technology will be enabled by fruitful partnerships between members of academia and industry players in the foldable electronics field.

Interested in other flexible and foldable electronics advancements? Learn more in the articles down below.

Flexible Processors? Arm and PragmatIC Push Flexible Electronics Up A Level

Developing Bendable and Entirely Flexible Electronics with A New Class of Films

The Air Force Bets on a Bright Future for Flexible Hybrid Electronics