Do Human-Compatible Soft Robots Have Good Taste?
Rachel Maya Gallagher posted on August 05, 2019 |

By combining engineered bacteria with a soft pressure-sensing gripper, researchers at the University of California, Davis (UC Davis) developed a robot with a sense of taste.

This pioneering soft robot senses the presence of the chemical isopropyl b-d-1-thiogalactopryanoside (IPTG) in a laboratory water bath, and uses that information to determine whether a plastic ball can safely be dropped into water.

The gripper deposits a ball in the water bath after determining that IPTG is not present. In this experiment, the robot took 10 hours to make its decision. (Image courtesy of UC Davis and Justus et al.)
The gripper deposits a ball in the water bath after determining that IPTG is not present. In this experiment, the robot took 10 hours to make its decision. (Image courtesy of UC Davis and Justus et al.)

Had the robot reached an incorrect conclusion about the presence of IPTG, it is unlikely that the little yellow ball would have been harmed by the chemical.

Combining chemical sensors with soft robotic actuators involved not only engineering bacteria to recognize IPTG and a mechanical gripper that could detect changes in pressure, but coupling the two systems via an organic-inorganic interface. Such an interface must allow for signal exchange with the environment while at the same time preventing the escape of engineered cells.

With optical transparency, elastomeric properties, and pore sizes of less than 0.5 mm in diameter, a PDMS-NaHCO3 membrane was chosen to house the engineered cells. A flexible printed circuit board (FlexPCB) was embedded in the PDMS biolayer and used to connect the cells to the gripper’s actuators.

At left, an expanded view of the gripper layers. At right, an illustration of the signaling pathway from the engineered E. coli cells to the soft robot actuators. (Image courtesy of UC Davis and Justus et al.)

When the synthetic bacteria came into contact with the IPTG, it triggered production of green fluorescent protein (GFP), which in turn created an optical signal that was transduced into electrical signals on the flexible circuit board. If no IPTG was sensed, the gripper was permitted to pick up the ball and place it in the bath.

An illustration of the process used by the robot to determine whether to place the plastic ball into the bath. If after six sampling attempts no IPTG had been detected, the robot added the object. Otherwise, it triggered an alert.
An illustration of the process used by the robot to determine whether to place the plastic ball into the bath. If after six sampling attempts no IPTG had been detected, the robot added the object. Otherwise, it triggered an alert.

Cells that process chemical information are space efficient by many orders of magnitude more than microprocessors that are programmed to perform the same task. This project is intended primarily as a proof of concept that intentionally utilizes a well-understood biosynthetic reaction to demonstrate the feasibility of integrated biological, electrical and robotic architecture.

Future endeavors will focus on adding multiple types of engineered bacteria to the soft robot’s arsenal, creating a synthetic microbiome that allows for increased sensory capabilities. The ultimate goal to increase the compatibility of soft robots with humans through embedded biosensors.

To learn more about soft robots, check out this pneumatic surface that molds to the human body in zero gravity. For synthetic cells that treat chemical imbalances, take a look at these bacteria being used for water treatment.


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