Being key components of the building envelope, glazing
products
with tunable optical properties are in great demand because of their
potential for boosting energy efficiency and privacy features while
enabling the main function of allowing natural light indoors. However,
windows and skylights with electric switching of haze and transparency
are rare and often require high voltages or electric currents, as
well as not fully meet the stringent technical requirements for glazing
applications. Here, by introducing a predesigned gel material we describe
an approach dubbed “Haze-Switch” that involves low-voltage
tuning of the haze coefficient in a broad range of 2–90% while
maintaining high visible-range optical transmittance. The approach
is based on a nanocellulose fiber gel network infiltrated by a nematic
liquid crystal, which can be switched between polydomain and monodomain
spatial patterns of optical axis via a dielectric coupling between
the nematic domains and the applied external electric field. By utilizing
a nanocellulose network of nanofibers ∼10 nm in diameter we
achieve <10 V dielectric switching and <2% haze in the clear
state, as needed for applications in window products. We characterize
physical properties relevant to window and smart glass technologies,
like the color rendering index, haze coefficient, and switching times,
demonstrating that our material and envisaged products can meet the
stringent requirements of the glass industry, including applications
such as privacy windows, skylights, sunroofs, and daylighting.