FlexEnable Bends OTFT Materials in Its Favor

Abstract

FOUNDED IN 2015 AND BASED IN CAMBRIDGE, ENGLAND, FlexEnable develops flexible organic electronic technologies, including liquid crystal (LC) optics and organic thin-film transistor (OTFT) materials. The company's focus is on replacing glass-based active optics and displays with flexible, conformable variants driven by OTFTs on flexible substrates. By using more flexible materials, the company enables optoelectronic modules that are ultrathin, ultralight, and robust and can be manufactured in existing display factories.

Rather than manufacturing consumer or commercial display products directly, FlexEnable partners with industry-leading display and device makers, bringing the company's OTFT materials, processes, and technology into existing facilities and fabrication. This allows display and device manufacturers to improve existing production processes and potentially tap into new markets.

FlexEnable's “secret sauce” is their ability to fabricate OTFTs at low temperatures, generally below 100°C (212°F). This allows for the use of lower-cost, commonly available, and optically ideal plastic and bioplastic substrates, such as triacetyl cellulose (TAC), which have excellent optical properties. The company says its OTFTs can bend to a radius of 0.1 mm thousands of times without affecting performance. This makes their technology a good choice for curved ePaper and organic LCD (OLCD) displays.

Beginning at Cavendish Labs at Cambridge University in 2000 as Plastic Logic, the company spun off as FlexEnable in 2015 with a vision to “bring surfaces to life” by seamlessly incorporating electronics into everyday objects that often do not have flat surfaces. This allows these objects to come alive with visual information, sensors, or other electronic functions, enhancing objects’ utility and appeal. With approximately 70 employees, the team is dedicated to developing OTFTs and brought the technology into mass production in 2024. It holds (or has applied for) around 500 patents.

While the company's initial focus was OTFT backplanes, its technology also has been used to develop biaxially formable LC cells on plastic using a low-temperature process. This has expanded the company's target markets by adding potential applications, such as lenses and ambient dimmers for augmented (AR) and virtual reality (VR) glasses (Fig. 1), ePrivacy screens for notebooks and mobile devices, and smart windows for cars.

“A big breakthrough for us that led to the formation of FlexEnable was to develop organic transistors that surpass the performance of amorphous silicon when manufactured in standard display fabs,” said Mike Banach, technical director. “Today, FlexEnable's OTFTs on plastic have mobility that is four times higher than that of amorphous silicon on glass as well as much lower electrical leakage. This has allowed us to work on product innovations in the areas of displays and optics and collaborate with world-leading companies. Our FlexiOM OTFT materials are now in production and shipping in CE products, and we are scaling up capacity to meet growing demand for flexible displays and optics.”

Being fabless can lead to advantages in capital preservation and efficiency, but it also could hinder a company's evolution by increasing their dependence on third parties for process capabilities and sales growth. According to Paul Cain, strategy director, this has not been a problem for FlexEnable.

“By focusing on our core strengths of flexible electronics technology and materials development, we can innovate at a faster pace,” said Cain. “We have a prototyping line in Cambridge that mirrors all the capabilities you'll find in an LCD fab. We work concurrently with both OEMs, who wish to evaluate custom advanced prototypes, and display fabs, who are setting up the processes and ramping production on their existing FPD lines. There are multiple applications for our technology, all of which are based on the same underlying core technology of LC optics and OTFTs manufactured on plastic.”

Cain said that the key to convincing display makers to adopt the FlexEnable technology is bringing real customer demand to the display maker and ensuring that the manufacturing process can be set up and begin production with existing equipment.

“We work concurrently with OEM/brands to build demand that is meaningful for fabs,” said Cain. “For example, we are commercially engaged with many of the largest CE brands for smartphone, mobile device, and AR/VR applications, which leads to very desirable demand for display fabs. We benefit from there being a considerable number of underutilized display fabs seeking differentiated products beyond glass LCD displays. Being fabless affords us greater flexibility to adapt to market changes and fluctuations in demand while collaborating with multiple manufacturing partners who specialize in different products.”

Although the company is headquartered in Cambridge, the team extends across multiple continents to best serve clients globally. The company has a chief revenue officer based in the United States to spearhead sales and business development efforts, while their business development manager in China focuses on cultivating relationships and opportunities throughout Asia.

To ensure efficient operations and support manufacturing partners in Asia, FlexEnable has teams in Cambridge and Taiwan. The Taiwan-based chief operating officer oversees strategic technology transfer projects, supported by the rest of the Asian team. In Cambridge, it undertakes OTFT materials formulation production, and these formulations are then shipped to fabrication partners worldwide (Fig. 2). This extended global footprint enables FlexEnable to leverage diverse expertise and resources.

When asked what sets the company apart from its competition, CEO Chuck Milligan said FlexEnable's greatest asset is their team. “As the only company offering a unique suite of low-temperature materials and processes, an in-house prototyping line, and several leading FPD and module assembly partners for mass production, we are uniquely positioned to empower our OEM customers to innovate and bring next-generation products to market faster.”

In June 2024, FlexEnable began commercializing OTFT materials, which are now embedded in the first mass-produced CE product driven by OTFT—a secure crypto wallet called “Ledger Stax,” developed by the French company Ledger (Fig. 3). FlexEnable partnered with display manufacturers DKE in Shanghai and Giantplus in Taiwan to realize Ledger's design for a credit card-sized product with an E Ink display wrapped around a 180-degree bend. Made of polymers instead of silicon, these OTFTs are manufactured directly onto plastic sheets instead of glass, making them thinner, lighter, and shatterproof.

FlexEnable's team has been thermoforming plastic LC cells to make biaxially curved pixelated dimmers and tunable lenses for AR and VR glasses (Fig. 4). By combining the advantages of thinness and lightness with the ability to stretch plastic transistors built on plastic, these form factors cannot be achieved with glass or silicon.

FlexEnable believes that curved and bendable displays are necessary to unlock greater design freedom and new use cases for consumer electronics and automotive. In addition to the Ledger Stax with its curved screen, the company sees AR and VR glasses as a prime candidate for its technology. Multiple developments are underway to make these products more visually comfortable (better displays and improved optics) while concurrently making them more physically comfortable (smaller and lighter) and damage resistant.

FlexEnable's ultrathin, light active optics enable tunable lenses and pixelated dimming films that allow virtual objects to be viewed clearly at a range of distances with high contrast even in bright lighting conditions (Fig. 5). This is particularly critical in AR applications, where the user needs to be visually aware while using the product.

In the automotive sector, electric vehicles (EVs) are driving the need for smart glass, including sunroofs and moonroofs. The trend in the EV market is toward fixed panoramic transparent roofs that do not open and stretch much of the length of the car or truck. Popularized by Tesla, these panoramic moonroofs are now available in multiple EVs from Porsche, Audi, Ford, and Hyundai (among others). FlexEnable's tintable LC films can be embedded into roof glazing, reducing weight while removing the need for additional sunroof mechanisms or extensive wiring. Because their OTFTs can be biaxially curved, this expands design options. They also can be segmented into different dimming regions and even pixelated, providing detailed light control.

Regarding laptops and cellular phones, protecting sensitive information is necessitating the demand for integrated ePrivacy screens. FlexEnable's LC cells on plastic can be built-in to displays at the point of manufacture, enabling a switchable viewing angle that provides privacy while adding near-zero thickness and weight to the devices.

According to FlexEnable, the primary challenge in creating flexible OTFTs has been producing a complete solution of “recipe and ingredients” for manufacturing the organic transistors. It is not enough to provide organic semiconductor materials to fabs. Display makers also need the complete transistor structure and associated low-temperature processes to build them on plastic. It is also important to develop auxiliary processes that allow these transistors to be integrated into complete modules that can interface with conventional electronics using standard protocols. A flexible or curved screen is only useful if it can be integrated with existing standards, control systems, and interfaces.

The company emphasizes the importance that each process step they develop be undertaken at a low temperature (less than 100°C), because that is key for building on optically ideal and low-cost plastic films.

“While handling flexible substrates presents unique challenges, we've addressed them through careful process optimization and equipment selection,” said Banach. “To accelerate time-to-market and reduce costs, we've leveraged existing fabrication facilities designed for conventional electronics. This approach allows us to repurpose existing infrastructure, minimizing upfront investments and enabling faster product development.”

When the company first started building OTFTs more than 20 years ago (at Cambridge University and Plastic Logic), those transistors’ mobility was around 100 to 1,000 times lower than inorganic amorphous silicon (a:Si) TFTs. But rather than be discouraged by the performance, the company pressed on.

According to Cain, “While the performance was significantly lower 20 years ago, the transistors were good enough for first applications, and performance advancements were happening frequently enough to give everyone a great deal of confidence in the continued trajectory. The transistor is such a fundamental building block of electronics that can be applied in so many places and applications, that the company never lost its belief in the technology. There are many examples of such fundamental platform technologies taking one to two decades to reach mass production.”

Since then, through improvements in materials and device architectures, OTFT mobility has risen to be well above a:Si (approximately 3–4 times higher), with equivalent or better stability. In addition, the company has focused on organic polymer semiconductors, because they form amorphous films that have excellent uniformity—a key property for large-area electronics.

In the company's view, low-temperature manufacturing (less than 100°C) is crucial for sustainable, scalable, and low-cost manufacturing of flexible electronics. Not only does it enable previously unimagined form factors, but the lower temperature drastically reduces energy consumption during manufacture. By switching from silicon to organic plastics, manufacturers can save approximately half the energy used in TFT production. The result—a flat or formed plastic imaging panel—is both lighter and more damage-resistant than glass, reducing shipping and breakage costs.

According to FlexEnable, their OTFTs can be manufactured in the same flat-panel display factories that use current methods and equipment, eliminating the need to build a new factory. Many factories have underutilized equipment that can be repurposed with this technology, prolonging its life and allowing display makers to enter new markets.

While it is still too early to announce many of the company's partnerships, FlexEnable currently has technology transfer programs and mass production underway with multiple leading display manufacturers in Asia as well as commercial programs with some of the biggest brands in consumer electronics. In addition to displays, there are several applications of ultrathin, light active LC optics coming soon.

“Achieving mass production of OTFT technology marks a major milestone for our company and guarantees our customers a clear path to mass production of game-changing optical modules and displays,” said Milligan. “We have established a robust supply chain that can support a wide range of future applications—and we're well-positioned to meet the volume requirements of our brand partners and capitalize on the massive $100 billion market opportunity for displays and active optical films.”