Using this method could advance technologies like memory devices and sensors, as well as pave the way to future soft materials that are both smart and flexible. 

Liquid crystals, which are used in liquid crystal display (LCD) screens for TVs and phones,  utilize their molecules to mimic the properties of both liquids and solids, giving them unique properties. While soft materials like liquids, gels and polymers have been widely used for their easy-to-process structures and lightweight properties, they tend to deform easily and often require replacement.

Everyday materials are made of molecules that align themselves in preferred directions. But liquid crystals could become much more useful if their molecules are all facing in one direction – obtaining what is called polar order.  

That can be difficult to do in soft materials, said Xiaoguang Wang, co-author of the study and an assistant professor in chemical and biomolecular engineering at The Ohio State University.

“Soft matter can’t compete with existing solid-state storage in speed, reliability or miniaturization, so the question becomes how might we control its internal structure to make it competitive or comparable to traditional hard materials,” said Wang. 

In searching for a solution, researchers found that they could program the movement of liquid crystals with the help of external forces, such as liquid or electricity. In this study’s case, water droplets were used to determine if scientists could influence the liquid crystal’s interface. 

First, the team etched pillars into a piece of silicon and infused liquid crystals between the spaces. Then a layer of water was introduced on top. 

Similarly to how a magnet’s north and south poles would react to a magnetic field, researchers saw that depending on where the droplet was moved, the molecules would immediately respond by pointing in that direction. By moving the droplet over the liquid crystals a second time, that movement could then be changed and pointed in a new direction, said Wang.

Significantly, the experiment also revealed that liquid crystal molecules could be taught to remember their orientation, opening up new ways for soft materials to exchange information without the need for electronics. “It can memorize the directionality of the information that we write into it, which means that our vector-based system operates like a memory device,” said Wang.

The study was recently published in Nature Physics.

While scientists are still working to incorporate this method into bigger projects, gaining the ability to control the position of liquid crystals’ molecules could lead not only to new functionalities for all sorts of technologies, but also new types of physics, said Ufuoma Kara, lead author of the study and a former graduate research associate at Ohio State.

“By imposing a greater level of polarity within these liquid crystal materials, we can explore new levels of applications,” he said. “Part of that includes expanding the amount of knowledge able to be embedded in their systems.” 

While it’s no easy feat, being able to cultivate materials with such abilities on a larger scale would suggest that the next generation of liquid crystals could one day act as both super-small computer processors and vast, reprogrammable memory storage devices. 

“There’s something very exciting in this discovery, and I think it’s a great foundation to spark some curiosity in young people who want to pursue this type of science,” said Kara.

Other co-authors include Boyuan Chen, Rajdeep Mamtani, Yang Xu, Alan Weible, Eric Boerner and Zhan Yang from Ohio State, as well as Simon Čopar and Uroš Tkalec from the University of Ljubljana, Shucong Li from the Georgia Institute of Technology, Yuxing Yao from the California Institute of Technology, and Robin L. B. Selinger from Kent State University.

This work is supported by the National Science Foundation, the Ohio State Materials Research Seed Grant Program, the Center for Emergent Materials, the Center for Exploration of Novel Complex Materials, and the Institute for Materials Research. 

The interface, dubbed ‘e-Taste’, uses a combination of sensors and wireless chemical dispensers to facilitate the remote perception of taste – what scientists call gustation. These sensors are attuned to recognize molecules like glucose and glutamate — chemicals that represent the five basic tastes of sweet, sour, salty, bitter, and umami. Once captured via an electrical signal, that data is wirelessly passed to a remote device for replication. 

Field testing done by researchers at The Ohio State University confirmed the device’s ability to digitally simulate a range of taste intensities, while still offering variety and safety for the user. 

“The chemical dimension in the current VR and AR realm is relatively underrepresented, especially when we talk about olfaction and gustation,” said Jinghua Li, co-author of the study and an assistant professor of materials science and engineering at Ohio State. “It’s a gap that needs to be filled and we’ve developed that with this next-generation system.”

The system, whose development was inspired by previous biosensor work of Li’s, utilizes an actuator with two parts: an interface to the mouth and a small electromagnetic pump. This pump connects to a liquid channel of chemicals that vibrates when an electric charge passes through it, pushing the solution through a special gel layer into the mouth of the subject. 

Depending on the length of time that the solution interacts with this gel layer, the intensity and strength of any given taste can easily be adjusted, said Li. 

“Based on the digital instruction, you can also choose to release one or several different tastes simultaneously so that they can form different sensations,” she said. 

The study was published today in the journal Science Advances. 

Taste is a subjective sense that can change from one moment to another. Yet this complex feeling is the product of two of the body’s chemical sensing systems working in tandem to ensure what you eat is safe and nutritious, the gustation and the olfactory (or smell) senses. 

“Taste and smell are greatly related to human emotion and memory,“ said Li. “So our sensor has to learn to capture, control and store all that information.” 

Despite the difficulty involved in replicating similar taste sensations for a majority of people, researchers found that in human trials, participants could distinguish between different sour intensities in the liquids generated by the system with an accuracy rate of about 70%. 

Further tests assessing e-Taste’s ability to immerse players in a virtual food experience also analyzed its long-range capabilities, showing that remote tasting could be initiated in Ohio from as far away as California. Another experiment involved subjects trying to identify five food options they perceived, whether it was lemonade, cake, fried egg, fish soup or coffee. 

While these results open up opportunities to pioneer new VR experiences, this team’s findings are especially significant because they could potentially provide scientists with a more intimate understanding of how the brain processes sensory signals from the mouth, said Li. 

Plans to enhance the technology revolve around further miniaturizing the system and improving the system’s compatibility with different chemical compounds in food that produce taste sensations. Beyond helping to build a better and more dynamic gaming experience, the study notes that the work could be useful in promoting accessibility and inclusivity in virtual spaces for individuals with disabilities, like those with traumatic brain injuries or Long Covid, which brought gustatory loss to mainstream attention. 

“This will help people connect in virtual spaces in never-before-seen ways,” said Li. “This concept is here and it is a good first step to becoming a small part of the metaverse.”

Other Ohio State co-authors include Shulin Chen, Yizhen Jia, Tzu-Li Liu, Qi Wang and Prasad Nithianandam and Chunyu Yang, including Bowen Duan and Zhaoqian Xie from Dalian University of Technology, Xiao Xiao and Changsheng Wu from the National University of Singapore, Xi Tian from Tsinghua University. 

This work was supported by the National Science Foundation, the National Institute Of Biomedical Imaging and Bioengineering, the Chronic Brain Injury Pilot Award Program at Ohio State, the Defense Advanced Research Projects Agency, the Center for Emergent Materials; the Center for Exploration of Novel Complex Materials, the Institute for Materials Research, the National Natural Science Foundation of China and the Dalian Outstanding Young Talents in Science and Technology.