With the rapid development of multimedia technology, an increasing number of emerging fields, such as virtual reality and wearable displays, have demanded high requirements for display technology, including high resolution, wide color gamut, and low-power consumption. The traditional display screen comprises three subpixels of red, green, and blue, which hamper further improvement of the display’s high resolution [1], [2].

Single-pixel displays of red, green, blue, and their mixed colors can exhibit considerably high display resolution and have thus become the focus of this research. Chun et al. vertically stacked two colors of light-emitting diodes (LEDs) to obtain LED that can emit blue, yellow, and their mixed colors [3]. Kang et al. realized a vertically stacked subpixel-type array structure in addition to a horizontally aligned subpixel-type structure that provides a threefold increase in display resolution over the horizontally aligned subpixel-type structure [4]. Kim et al. achieved displays of red, green, blue, and their mixed colors by vertically stacking red, green, and blue LEDs in a 4μm single pixel such that their array density reached 5100 pixels/inch [5].

However, current research on single-pixel panchromatic displays is mainly focused on active devices, such as LEDs, with less focus on passive devices. Recently, Xu et al. reported that the position of graphene in the microcavity can be changed by adjusting the voltage to change the deformation of graphene, thus realizing the display of monochrome light or multiple mixed colors within a single pixel [6]. To achieve this, they combined graphene micro-electrical-mechanical system (MEMS) with three resonant standing-wave-mode photonic crystal microcavities with corresponding wavelengths of red, green, and blue primary colors. Compared with conventional MEMS [7], [8], [9], graphene has superior mechanical and optoelectronic properties, higher Young’s modulus, larger specific surface area, considerably low surface density, and excellent ductility [10], [11], [12], [13], [14], [15], [16], [17]. Hence, electro-optical modulators of graphene MEMS have been successfully applied in optical projectors and simplified spectrometers [18]. For instance, Dejan Davidovikj et al. used a phase-sensitive interferometer to visualize the vibrations of micrometer-scale graphene nanodrums at extremely high frequencies [19]. Furthermore, Houri et al. discovered that a bilayer graphene membrane can reproduce the interference effects of an interferometric modulator display. Under white light illumination, the downward-bending bilayer graphene membrane displayed Newton’s rings when the pressure difference between the inside and outside layers of the cavity was 1 bar [20]. Furthermore, they studied the electro–optical response of bilayer graphene pixels and successfully manufactured a reflective graphene-based display with a high-resolution image (2500 pixels/inch) [21]. This experiment highlighted the ability of graphene films to reproduce excellent colors under electro–optical modulation, making the films an ideal choice for high-resolution pixel displays. Displays based on graphene mechanical pixels are ultrathin and exhibit high resolution; moreover, they are more durable, energy-efficient, flexible, and easy to control compared with LED screens. However, current graphene MEMS is mainly based on the elastic deformation of graphene [18], [22], [23]; the spontaneous oscillations due to large strain energy cause graphene MEMS to achieve high-performance MEMS oscillators [24], [25], [26] rather than light modulators.

Herein, we introduced yarn muscles into our design to further reduce the large deformation energy caused by the elastic deformation of graphene, reduce the modulation voltage and energy consumption, and expand its color gamut. Yarn muscle refers to a device that can reproduce the movement of a living organism via reversible contraction and expansion of materials in response to a specific stimulus, which is similar to muscles responding to a neural signal [27]. Yarn muscles stretch, contract, twist, rotate, or bend by converting the input electrical, thermal, or chemical energy into mechanical energy under external heat, light, or electrical stimulation [28], [29], [30], [31], [32]. Owing to their small size, high freedom of motion, good environmental adaptability, and absence of large deformation energy and spontaneous vibration, yarn muscles have broad application prospects in robotics, flexible mechanical electronics, biomedicine, and precision minimally invasive surgery [33], [34], [35], [36]. These devices, based on yarn muscles, are optically controllable. Furthermore, they exhibit a remarkable ability to lift objects weighing more than 650 times their own weight and can withstand a strain of up to 1000%. Additionally, they demonstrate long-term elasticity and resilience even after undergoing 105 cycles of deformation [37]. Moreover, yarn muscles are highly scalable and have reversible properties, enabling them to contract and relax under electric field stimulation; thus, yarn muscles are an effective means of controlling and regulating graphene MEMS. Previous studies have shown that precise control of the voltage applied to graphene thin films can accurately control the equilibrium position of graphene during its bending [6], [21]. Furthermore, Weifeng Liu et al. developed an electrically programmable yarn muscle material. By varying the current value from 5 to 30 mA, the reversible driven strain can reach 20% [38]. A comparison of the required power densities reported in related studies shows that the introduction of yarn muscles can reduce the deformation energy and lower the energy consumption.

In particular, photonic crystal microcavities were designed with three resonant standing wave modes corresponding to red, green, and blue primary wavelengths. The motion of graphene in the microcavity is facilitated by yarn muscles. When graphene is positioned in a region of higher light intensity, it absorbs a greater amount of light, resulting in diminished transmittance. Conversely, when it is positioned in a region of lower light intensity, it absorbs less light, leading to increased transmittance. Hence, by adjusting the stretching and contracting of the yarn muscles, control is achieved over the position of graphene within the microcavity and thereby over the modulation of its absorption and transmittance properties. Because different colors of light have different wavelengths, they exhibit different field distributions in the microcavity. Therefore, to change the position of graphene in the microcavity, the absorption of graphene toward different colors of light is first adjusted and an output of monochromatic light or multiple mixed colors of light within a single pixel is subsequently realized. This study can provide guidance and new ideas for designing and fabricating low-power, ultrahigh-resolution, ultrawide-color-gamut interference modulator display technology.