Soft robot has advantages of flexible actuating strategies, various patterns of movement, and friendly interaction with humans. However, due to the lack of suitable practical methods and soft controllers, fabricating a fully integrated flexible robot remains a major challenge.   

Based on the deformation and locomotion behavior of liquid metals (LMs) via electrical stimulus, Prof. LIU Jing's team from the Technical Institute of Physics and Chemistry (TIPC) of the Chinese Academy of Sciences proposed and demonstrated a new type of liquid metal droplet electronic device. The new device could be organized further into gate logics to execute logical computing.

The study, published in Advanced Intelligent Systems on March 18, showed the importance of LMs in intelligent electronic control systems for the first time. It also provided a new method to manufacture soft electronic devices.  

"As a new class of smart materials, liquid metal is inherently flexible, electrically conductive and responsive to stimuli. It is highly possible to develop soft intelligent electronic devices and explore the potential application of LMs in control systems," said Prof. LIU.  

The new device removes the reliance on semiconductor by directly constructing electronic devices on soft materials to perform logical operations and calculations.   

A variety of logic gates can be easily manufactured through different connections to liquid metal droplets electronic devices, which have shown stable functionality for binary logic calculation.   

To demonstrate the feasibility of application, researchers constructed a soft four-degree logic accumulator via LMs droplet electronic device, which could regulate a pneumatic soft gripper within four states of inflation.   

The spatial scale of LM involved motion is quite small without bulky ancillary equipment and easy for miniaturization and integration.   

In this research, the trial of LM-based logic devices demonstrated the potential that electrically-induced variations of liquid in a macroscale could be designed as processors for reception, conversion and exportation of electrical signals. Owing to the natural harmony with soft structures, they may hold a promise for the ultimate autonomy and control of soft robots in the near future. 

Structural principles of LM droplet electronic devices (Image by LIU Jing et al.)