We report a method of obtaining controllable spatially varying liquid crystal pretilt angles using a stacked alignment layer. The stacked alignment layer consists of nano-domains of horizontal and vertical alignment materials. The pretilt angle is controlled by varying the domain ratio of the two layers. By using photoalignment material as the top layer, the pretilt angle can be controlled by varying the UV light dosage. A spatially variable UV light beam can be used to control the pretilt angle spatially. An electrically tunable-focus liquid crystal lens is obtained using this method.

A simple projected capacitive touch panel is developed. This touch panel is capable of detecting multi‐point touch events. The device consists of a single piece of patterned transparent ITO glass and a sensing circuit. The applied driving signal is projected onto the sensing node in the form of an electric field. A charge sensing circuit is used to monitor the mutual capacitance between the driving and sensing nodes. This approach provides a simple and low cost alternative to current capacitive multi‐touch panel design.

We investigate the behavior of liquid crystal dynamic flow in a cell with a bidirectional alignment ͑BDA͒ surface. Numerical simulations show that with a BDA surface having a pitch comparable to the cell gap d, the liquid crystal dynamic flow direction can be controlled by the driving voltage. Such an effect can be applied to bistable twisted nematic displays without the need for anchoring breaking. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3080198͔There are numerous studies of liquid crystal ͑LC͒ dynamic flow on homogenous alignment surfaces. Van Doorn et al. 1 stated that dynamic flow imparts a backward torque on the LC molecules near the center of the device. Berreman et al.2 observed this phenomenon on twisted nematic devices. Bos and Koehler 3 reported that faster LC display response can be achieved by removing this backflow effect. They suggested that for the bend deformation, the backward torque can be eliminated. For the case of bistable twisted nematic ͑BTN͒ devices, dynamic backflow is essential to the switching mechanism. Dozov et al. 4 proposed a switching mechanism based on asymmetric anchoring alignment ͑strong polar anchoring on the master plate and weak polar anchoring on the slave plate͒. When the electric field is turned off rapidly, the master plate director rotates and creates a dynamic flow on the slave plate. Therefore, the cell relaxes rapidly to the transient bend state and then to the -twisted state. If the applied electric field decreases slowly, the backflow effect is weak and the device will relax adiabatically to the homogenous state.It is obvious that the dynamic flow of the LC is very important to determine the dynamic performance of the LC device. In this paper, we propose a new method to control LC flow dynamics using a bidirectional alignment ͑BDA͒ layer. In the following, the mechanism of such idea will first be explained. Then, we demonstrate the idea by applying this technology to the BTN device. A new BTN display, called multidomain BTN ͑MD-BTN͒, which switches between the no-twist and -twisted states, has successfully been fabricated.The BDA surface is a heterogeneous alignment surface with a periodic pattern. Figure 1 shows the detailed structure of the BDA. It has a periodicity of L and is composed of two types of domains D 1 and D 2 . D 1 and D 2 have different pretilt angles 1 and 2 , respectively, on the same plane. The LC molecules are tilted in opposite directions so that 1 + 2 is always larger than 90°. It is intuitively obvious that the LC molecules are either tilted at 1 or 2 , respectively, on the BDA surface, and then relax to a uniform tilt angle in a distance L H , which is determined by the pitch L. The LC deformation inside the bulk system can be calculated by minimizing the total energy consisting of the bulk elastic energy and surface anchoring energywhere n denotes the LC director, W i is the finite polar surface anchoring energy of the domains, and F͑n͒ is the FrankOseen elastic energy given bywhere K 11 , K 22 , and K 33 are the splay, tw...