# Nematic Liquid Crystal Composite Materials for DC and RF Switching
## 7 Discussion
Microfabrication and alignment: Most of the reported work on field-induced switching is done on conventional LC-sandwiched cells made of ITO-coated glass. These are macroscale devices and are easy to fabricate. According to our simulation results, to meet the RF switching requirement, devices need to be scaled down to microscale. However, in microscale, electrode deposition and making an alignment layer is a challenge. However, there are some works on the microfabrication of LC-based devices. For example, [PERSON] et al. demonstrated an LC phase shifter using inverted microstrip line configuration [107]. [PERSON] et al. described a fabrication technique for an in-plane LC-CNT-based device made of interdigitated electrodes for gas sensing application [108]. [PERSON] et al. used photolithography-patterned graphene electrodes instead of ITO for a better optical transmission characteristic of LC devices. Besides fabrication complexity in microscale, making alignment layers could be challenging. However, some groups demonstrated alignment LC in microscale. [PERSON] et al. described a micro-rubbing technique for LC alignment [109]. Nano-imprint lithography could be used for patterned alignments in microscale [110; 111; 112]. Photo-induced alignment is another option for patterned alignments in microscale. Along with these, a few other micro-patterning techniques are also reported [113; 114]. 2. CNT has a tendency to aggregate in an LC solution. This is responsible for the poor CNT solubility in LC solutions. The dispersion quality degrades with time. A very common way to make a homogeneous dispersion is a magnetic string followed by sonication [115; 116]. 3. Reversible switching will be a challenge as LC-CNT composites show the memory effect. Considering this issue, DFNLC is a good option, but in this case, the switching ratio is only 170 as reported by [PERSON] et al [84]. An in-plane cross-electrode configuration [70] is a viable solution, but this will bring additional fabrication complexity. In addition to this, repeatable measurement behavior is also desired. 4. In most of the reported works, an AC electric field is applied for switching to avoid ion migration during switching. For DC switching, the materials need to be ion-free. 5. During conductivity switching, Joule heating may occur, which drives the system from a nematic to isotropic phase [20; 53]. If the sample is subjected to heating for a long time, chemical degradation may occur. To prevent this, the system should be operated in constant current mode. Another way to prevent the phase changing is to keep the system in a constant temperature using a feedback system. 6. To design an efficient switch, dynamical and transient behaviors need to be studied. However, there are few reports on the dynamical switching behavior. From the work of [PERSON]. [PERSON] et al., it seems the switching can take place within a few seconds [70]. [PERSON] et al. observed the field-induced isotropic bubble formation around the CNT bundles within a second [53]. [PERSON] et al. demonstrated that switching occurs within 1-5 ms [24]. According to the discussion above, we found that a 5 CB/CNT composite might be best-suited for switching applications. As 5 CB/CNT shows a near room-temperature operation (both in the nematic and isotropic phase) with more than three orders of magnitude switching. We chose this material for our RF simulations. We did an RF simulation as a proof of concept.