2D breathable graphene-based windows for smart sustainable housing

The next generation of smart multifunctional structures and devices requires the development of materials with sensing/actuating properties such as the capability to sense and respond to triggers, adapt to the environment, and switch their properties and functions on demand. Here, we propose a novel concept of sensing/actuating in 2D materials based on both in-plane and out-of-plane rearrangement of 2D flakes on demand. To form such breathable in three dimensions 2D materials, we develop a novel approach to regulate interactions between GO flakes using pH. In this work, we program the sensing/actuating properties of 2D graphene-based multilayers by pH-assisted tuning of the interactions between the flakes to achieve 2D lateral length and area change. Simultaneously, our one-stage method leads to the self-assembly of multilayers with out-of-plane anisotropy to fulfill the requirements of bending theory. Due to the versatility of our approach, it is also applicable to other 2D materials with adjustable surface charge density such as MXenes. Furthermore, we apply the “bimetallic strip model” to calculate the thermal expansion coefficients for our charged and uncharged 2D materials. This model explains the change in the physical state of metals by lateral expanding or deforming that is applicable to 2D materials. We apply our lightweight low dimensional breathable materials to construct flamboyant windows that can open/close in response to a tiny change in room climate during the day. Our inspired by gothic architecture flamelike 2D windows provides energy saving climate control and novel concept in the functional design of sustainable houses. Importantly, this work gives a novel insight into the mechanism of bending/unbending of 2D materials. We show that our approach is applicable to the whole family of 2D materials with regulated surface charge density from GO to MXenes. Such 2D actuators are robust, thin, and flexible and can be used for soft robotics and energy-efficient architecture, tissue engineering, bionic devices, and biomedical applications.