Tissue-Integrated Sensing and Control

Introduction

Adaptive and intelligent biohybrid robots must incorporate closed-loop control by integrating bioactuators and sensors capable of understanding their biomechanical state and subsequently regulating the actuation responses. Feedback control systems for biohybrid robotics are needed to transform muscle tissue-based bio-actuators into decision-making dynamic machines. The engineered skeletal muscle tissue that we use as bio-actuator is very soft and small. Thus, when it comes to incorporate a sensor for real time reporting on the deformation state of the muscle, the main challenges is to find sensor technologies that are miniaturized, soft, biocompatible, highly sensitive, and operative in the liquid environment of cell cultures exposed to electrical fields used to stimulate the contraction of our bio-actuators.

Sensing Fiber

In collaboration with the Dr. Frank Clemens group at EMPA, we developed a soft, fiber-shaped mechanical sensor based on a piezoresistive composite that efficiently integrates with engineered skeletal muscle tissue and senses its contracting states in a cell culture environment in the presence of applied electrical fields. We insulated the sensor' and assess its biocompatibility. Its high sensitivity is useful to detect strains that typical of the engineered skeletal muscle tissue (<1%), and was found capable of detecting motions from contractile skeletal muscle tissue constructs. Finally, we design a closed-loop control system in which the sensor response can feed an autonomous control paradigm. This sensor allowed us to demonstrate the first proprioceptive biohybrid robot that senses and responds to its contraction state.

Sensing Hydrogels

Being flexible, soft, and tissue-adhesive, conductive hydrogels offer promising uses in the realm of both flexible bioelectronics and intelligent engineered tissue models. In collaboration with the Soft Materials Group of Prof. Esther Amstad at EPFL, we developed a piezoresistive hydrogel to serve as soft, bio-integrated hydrogel that is optimized for mechanical stimuli detection within tissues. Our conductive organohydrogel is highly stretchable and can be co-printed with a muscle cell-laden bioink to generate tissue models with complex architectures. Our tissue-embedded sensor acts as a flexible strain sensor to monitor both bulk and localized mechanical inputs and has the potential for mechanosensing space mapping in 3D cell culture models. Our organohydrogel-integrated tissue will serve to build bio-hybrid robots with complex and finely distributed networks of sensors, and provide novel insights to bio-integrated flexible sensors for biomechanics research and tissue engineering applications.
 

Applications

Understanding biomechanics in 3D cell culture models is crucial for replicating the tissue development process for tissue engineering applications. Due to interface instability and design constraints, integrating soft tissue with technologies for real-time measurements of mechanical inputs is challenging. However, we are excited to work on sensorizing the engineered tissue, as this innovation has prospective applications in bio-hybrid robotics, as well as in sensor technologies, bioelectronics, tissue engineereg models, and biomechanics.

Authors Involved

This research was conducted by a collaborative team from the Soft Robotics Lab at ETH Zurich, including:

• Miriam Filippi
• Aiste Balciunaite
• Asia Badolato
• Robert K. Katzschmann

Relevant Publications