Search for: All records

Microelectromechanical systems (MEMS) assembly into packages that interface with the environment is critical in electronic sensor applications ranging from soft biomedical systems to telecommunications. This article presents a novel process using heat-depolymerizable polyethylene carbonate (QPAC-25) as a sacrificial tether, and demonstrates it for assembling waferbound MEMS onto wires. The assembly mechanism is thermal removal of the tether, allowing a strained layer to pop up from the substrate and make electrical and mechanical contact with the wire. We detail the QPAC-25 fabrication procedures, characterize the relationship between QPAC-25 thickness and spin speed and determine a route to pattern QPAC-25 without a metal hard mask or photosensitizers 

In this work, we present two embedded soft optical waveguide sensors designed for real-time onboard configuration sensing in soft actuators for robotic locomotion. Extending the contributions of our collaborators who employed external camera systems to monitor the gaits of twisted-beam structures, we strategically integrate our OptiGap sensor system into these structures to monitor their dynamic behavior. The system is validated through machine learning models that correlate sensor data with camera-based motion tracking, achieving high accuracy in predicting forward or reverse gaits and validating its capability for real-time sensing. Our second sensor, consisting of a square cross-section fiber pre-twisted to 360 degrees, is designed to detect the chirality of reconfigurable twisted beams. Experimental results confirm the sensor’s effectiveness in capturing variations in light transmittance corresponding to twist angle, serving as a reliable chirality sensor. The successful integration of these sensors not only improves the adaptability of soft robotic systems but also opens avenues for advanced control algorithms. 

This paper presents the novel use of air gaps in flexible optical light pipes to create coded patterns for use in bend localization. The OptiGap sensor system allows for the creation of extrinsic intensity modulated bend sensors that function as flexible absolute linear encoders. Coded air gap patterns are identified by a Gaussian naive Bayes (GNB) classifier running on an STM32 microcontroller. The fitting of the classifier is aided by a custom software suite that simplifies data collection and processing from the sensor. The sensor model is analyzed and verified through simulation and experiments, highlighting key properties and parameters that aid in the design of OptiGap sensors using different light pipe materials and for various applications. The OptiGap system allows for real-time and accurate bend localization in many robotics and automation applications, in both wet and dry conditions. 

This paper presents the concept of creating virtual joints in soft robotic structures by modifying the local curvature of non-stretchable thin-walled structures through shape memory alloy (SMA)-based surface actuation. A thin planar flexible material can be stiffened by curving it along one axis, which increases stiffness by increasing the effective thickness. Locally deforming the curved sheet by making a flat region reduces this thickness, creating a defect. The material buckles and bends in a controlled manner at that location under an external force, producing a virtual compliant joint. We use tailored wire placement techniques to embed a continuous SMA wire in a serpentine pattern into denim cloth stiffened by a thin plastic film. When curved, joints can be created in this structure by activating small segments of the SMA wire using Joule heating which induces local curvature, with each of these segments able to exert up to 1.6 N of force. Finally, we present a circuit and algorithm for routing current through any desired SMA wire segment(s). Experimental results show that compliant joints can be created anywhere along the structure, resulting in a reconfigurable system. 

Fabrics and fibrous materials offer a soft, porous, and flexible substrate for microelectromechanical systems (MEMS) packaging in breathable, wearable formats that allow airflow. Device-on-fiber systems require developments in the field of E-Textiles including smart fibers, functional fiber intersections, textile circuit routing, and alignment methods that adapt to irregular materials. In this paper, we demonstrate a MEMS-on-fabric layout workflow that obtains fiber intersection locations from high-resolution fabric images. We implement an image processing algorithm to drive the MEMS layout software, creating an individualized MEMS “gripper” layout designed to grasp fibers on a specific fabric substrate during a wafer-to-fabric parallel transfer step. The efficiency of the algorithm in terms of a number of intersections identified on the complete image is analyzed. The specifications of the MEMS layout design such as the length of the MEMS gripper, spatial distribution, and orientation are derivable from the MATLAB routine implemented on the image. Furthermore, the alignment procedure, tolerance, and hardware setup for the alignment method of the framed sample fabric to the wafer processed using the custom gripper layout are discussed along with the challenges of the release of MEMS devices from the Si substrate to the fabric substrate.