Carmel Majidi

Carnegie Mellon University | CMU · Department of Mechanical Engineering

This paper builds a Near-Field Communication (NFC) based localization system that allows ordinary surfaces to locate surrounding objects with high accuracy in the near-field. While there is rich prior work on device-free localization using far-field wireless technologies, the near-field is less explored. Prior work in this space operates at extreme...

Background An objective measurement of chronic itch is necessary for improvements in patient care for numerous medical conditions. While wearables have shown promise for scratch detection, they are currently unable to estimate scratch intensity, preventing a comprehensive understanding of the effect of itch on an individual. Methods In this work,...

Soft and stretchable electronics have diverse applications in the fields of compliant bioelectronics, textile‐integrated wearables, novel forms of mechanical sensors, electronics skins, and soft robotics. In recent years, multiple material architectures have been proposed for highly deformable circuits that can undergo large tensile strains without...

Physically soft magnetic materials (PSMMs) represent an emerging class of materials that can change shape or rheology in response to an external magnetic field. However, until now, no studies have investigated using an electropermanent magnet (EPM) and magnetic repulsion to magnetically deform PSMMs. Such capabilities would enable the ability to de...

The recent popularity of soft robots for marine applications has established a need for the reliable fabrication of actuators that enable locomotion, articulation, and grasping in aquatic environments. These actuators should also reduce the negative impact on sensitive ecosystems by using biodegradable materials such as organic hydrogels. Freeform...

Soft electromagnetic devices have great potential in soft robotics and biomedical applications. However, existing soft-magneto-electrical devices would have limited hybrid functions and suffer from damaging stress concentrations, delamination or material leakage. Here, we report a hybrid magnetic-mechanical-electrical (MME) core-sheath fiber to ove...

Despite advances in soft, sticker‐like electronics, few efforts have dealt with the challenge of electronic waste. Here, this is addressed by introducing an eco‐friendly conductive ink for thin‐film circuitry composed of silver flakes and a water‐based polyurethane dispersion. This ink uniquely combines high electrical conductivity (1.6 × 10⁵ S m⁻¹...

Over the years, efforts in bioinspired soft robotics have led to mobile systems that emulate features of natural animal locomotion. This includes combining mechanisms from multiple organisms to further improve movement. In this work, we seek to improve locomotion in soft, amphibious robots by combining two independent mechanisms: sea star locomotio...

Liquid metals, with their unique combination of electrical and mechanical properties, offer great opportunities for actuation based on surface tension modulation. Thanks to the scaling laws of surface tension, which can be electrochemically controlled at low voltages, liquid metal actuators stand out from other soft actuators for their remarkable c...

Despite the impressive performance of recent marine robots, many of their components are non‐biodegradable or even toxic and may negatively impact sensitive ecosystems. To overcome these limitations, biologically‐sourced hydrogels are a candidate material for marine robotics. Recent advances in embedded 3D printing have expanded the design freedom...

Polymer networks formed by cross linking flexible polymer chains are ubiquitous in many natural and synthetic soft-matter systems. Current micromechanics models generally do not account for excluded volume interactions except, for instance, through imposing a phenomenological incompressibility constraint at the continuum scale. This work aims to ex...

Polymer networks formed by cross linking flexible polymer chains are ubiquitous in many natural and synthetic soft-matter systems. Current micromechanics models generally do not account for excluded volume interactions except, for instance, through imposing a phenomenological incompressibility constraint at the continuum scale. This work aims to ex...

Suspending microscale droplets of liquid metals like eutectic gallium-indium (EGaIn) in polydimethylsiloxane (PDMS) has been shown to dramatically enhance electrical permittivity without sacrificing the elasticity of the host PDMS matrix. However, increasing the dielectric constant of EGaIn-PDMS composites beyond previously reported values requires...

Liquid crystal elastomers (LCEs) have grown in popularity in recent years as a stimuli-responsive material for soft actuators and shape reconfigurable structures. To make these material systems electrically responsive, they must be integrated with soft conductive materials that match the compliance and deformability of the LCE. This study introduce...

Kirigami, a traditional paper‐cutting art, is a promising method for creating mechanically robust circuitry for unconventional devices capable of extreme stretchability through structural deformation. In this study, this design approach is expanded upon by introducing Liquid Metal based Elastic Kirigami Electrodes (LM‐eKE) in which kirigami‐pattern...

Development of soft and compliant actuators has attracted tremendous attention due to their use in soft robotics, wearables, haptics, and assistive devices. Despite decades of progress, the goal of entirely digitally-printed actuators has yet to be fully demonstrated. Digital printing permits rapid customization of the actuator's geometry, size, an...

Liquid crystal elastomers (LCEs) are becoming increasingly popular as a shape memory material for soft robot actuators that operate in a contractile or flexural mode. There have been previously studies on the use of LCEs for reversible changes in surface topography. However, surface protrusions have typically been limited to the order of 1 μm or de...

Self-healing hydrogels use spontaneous intermolecular forces to recover from physical damage caused by extreme strain, pressure or tearing. Such materials are of potential use in soft robotics and tissue engineering, but they have relatively low electrical conductivity, which limits their application in stretchable and mechanically robust circuits....

Soft materials that exhibit the compliance, programmability, and reconfigurability could have transformative impact as electronic skin for applications in wearable electronics/soft robotics. There has been significant progress in soft conductive materials; however, achieving electrically‐controlled and reversible changes in conductivity and circuit...

Magnetically actuated miniature machines can perform multimodal locomotion and programmable deformations. However, they are either solid magnetic elastomers with limited morphological adapt ability or liquid material systems with low mechanical strength. Here, we report magnetoactive phase transitional matter (MPTM) composed of magnetic neodymium-i...

Multichamber soft pneumatic actuators (m‐SPAs) are widely used in soft robotic systems to achieve versatile grasping and locomotion. However, existing m‐SPAs have slow actuation speed and are either limited by a finite air supply or require energy‐consuming hardware to continuously supply compressed air. Herein, these shortcomings by introducing an...

Liquid metal embedded elastomers (LMEEs) are highly stretchable composites comprised of microscopic droplets of eutectic gallium‐indium (EGaIn) liquid metal embedded in a soft rubber matrix. They have a unique combination of mechanical, electrical, and thermal properties that make them attractive for potential applications in flexible electronics,...

Soft Robots In article number 2201259, Dinesh K. Patel, Xiaonan Huang, Lining Yao, Carmel Majidi, and co‐workers present highly dynamic, robust, and fast‐responding bistable actuators for use in soft robotics. These actuators use 3D printed soft materials and shape memory alloy for rapid motions with 1 Hz frequency. They enable the creation of reco...

Stretchable electronics is playing an integral role in fields such as wearable electronics and soft robots. Among soft conductive materials, liquid metal is drawing intense attention as an electrode material due to its liquid nature at room temperature. However, the merits of liquid metal conductor are limited by the presence of substrates or enclo...

Miniature magnetic soft machines could significantly impact minimally invasive robotics and biomedical applications. However, most soft machines are limited to solid magnetic materials, whereas further progress also relies on fluidic constructs obtained by reconfiguring liquid magnetic materials, such as ferrofluid. Here we show how harnessing the...

Liquid metal embedded elastomers (LMEEs) are composed of a soft polymer matrix embedded with droplets of metal alloys that are liquid at room temperature. These soft matter composites exhibit exceptional combinations of elastic, electrical, and thermal properties that make them uniquely suited for applications in flexible electronics, soft robotics...

Shape memory materials such as liquid crystal elastomers (LCE) have been explored as soft robotic actuators due to their high mechanical robustness and muscle-like work densities. The main drawback of LCEs is slow response times and low energy efficiencies stemming from poor thermal management. Thermoelectric devices (TED), which generate temperatu...

Matching the rich multimodality of natural organisms, i.e., the ability to transition between crawling and swimming, walking and jumping, etc., represents a grand challenge in the fields of soft and bio‐inspired robotics. Here, a multimodal soft robot locomotion using highly compact and dynamic bistable soft actuators is achieved. These actuators a...

High cost and lack of reliability has precluded the widespread adoption of dexterous hands in robotics. Furthermore, the lack of a viable tactile sensor capable of sensing over the entire area of the hand impedes the rich, low-level feedback that would improve learning of dexterous manipulation skills. This paper introduces an inexpensive, modular,...

Having accurate localization capabilities is one of the fundamental requirements of autonomous robots. For underwater vehicles, the choices for effective localization are limited due to limitations of GPS use in water and poor environmental visibility that makes camera-based methods ineffective. Popular inertial navigation methods for underwater lo...

Multi-chamber soft pneumatic actuators (m-SPAs) have been widely used in soft robotic systems to achieve versatile grasping and locomotion. However, existing m-SPAs have slow actuation speed and are either limited by a finite air supply or require energy-consuming hardware to continuously supply compressed air. Here, we address these shortcomings b...

Legged robots constructed from soft materials are commonly claimed to demonstrate safer, more robust environmental interactions than their rigid counterparts. However, this motivating feature of soft robots requires more rigorous development for comparison to rigid locomotion. This article presents a soft legged robot platform, Horton, and a feedba...

Soft fluidic robots are typically controlled using manifolds containing large and rigid electromechanical valves. These bulky controllers limit scalability and hinder motion, in particular for untethered soft robots. There has been recent interest in using fluidic controllers analogous to electrical logic gates and microcontrollers to replace rigid...

A novel architecture of materials and fabrication techniques is proposed that serves as a universal method for implementation of thin‐film biostickers for high resolution electrophysiological monitoring. Unlike the existing wearable patches, the presented solution can be worn for several days, and is not affected by daily routines such as physical...

Although soft robots show safer interactions with their environment than traditional robots, soft mechanisms and actuators still have significant potential for damage or degradation particularly during unmodeled contact. This article introduces a feedback strategy for safe soft actuator operation during control of a soft robot. To do so, a supervis...

Progress in artificial muscles relies on new architectures that combine soft matter with transduction mechanisms for converting controlled stimuli into mechanical work. Liquid metal, in particular eutectic gallium–indium (EGaIn), is promising for creating an artificial muscle since it is intrinsically deformable and capable of generating significan...

Because they are made of elastically deformable and compliant materials, soft robots can passively change shape and conform to their environment, providing potential advantages over traditional robotics approaches. However, existing manufacturing workflows are often labor intensive and limited in their ability to create highly integrated three-dime...

Printed soft conductive materials for stretchable electronics should have low electrical resistivity, high strain limit, and stable electrical properties when stretched. Previously, it has been shown that a bi‐phasic ink composed of silver (Ag) microflakes, eutectic gallium−indium (EGaIn) alloy, and styrene isoprene (SIS) block copolymer is a promi...

Intelligent magnetic soft robots capable of programmable structural changes and multifunctionality modalities depend on material architectures and methods for controlling magnetization profiles. While some efforts have been made, there are still key challenges in achieving programmable magnetization profile and creating heterogeneous architectures....

Liquid crystal elastomers (LCE) have attracted tremendous interest as actuators for soft robotics due to their mechanical and shape memory properties. However, LCE actuators typically respond to thermal stimulation through active joule heating and passive cooling, which make them difficult to control. In this paper, we combine LCE with soft, stretc...

Untethered soft robots that locomote using electrothermally-responsive materials like shape memory alloy (SMA) face challenging design constraints for sensing actuator states. At the same time, modeling of actuator behaviors faces steep challenges, even with available sensor data, due to complex electrical-thermal-mechanical interactions and hyster...

Liquid‐metal (LM)‐based soft and stretchable electronics (SSEs) provide unique advantages for wearable computing, soft robotics, and implantable devices applications involving physical interaction with biological tissues and delicate objects. However, the lack of scalable manufacturing techniques prevents their mainstream adoption and commercializa...

The efficient motility of invertebrates helps them survive under evolutionary pressures. Reconstructing the locomotion of invertebrates and decoupling the influence of individual basic motion are crucial for understanding their underlying mechanisms, which, however, generally remain a challenge due to the complexity of locomotion gaits. Herein, we...

Soft polymers embedded with liquid metals like eutectic gallium-indium (EGaIn) exhibit unique combinations of mechanical, electrical, and thermal properties that are not possible with other material systems. For example, a soft silicone elastomer embedded with a percolating network of EGaIn microdroplets can function as a highly soft and elastic co...

The characterization of an RF transmitter composed of insulating and conducting regions of liquid‐metal embedded elastomer (LMEE) is presented along with in situ measurements of LMEE microstrip lines as they are subjected to local material strains up to 40%. The LMEE is comprised of microscale droplets of a gallium‐indium alloy that is liquid at ro...

Surgical planning to visualize a complete procedure before surgical intervention, paired with the advanced surgical techniques of a surgeon, has been shown to improve surgical outcomes. Efforts to improve surgical planning have included tracking real-time surgeon movements via surgical instruments in a confined body cavity space in the human body t...

Control of soft robotic manipulators remains a challenge for designs with advanced capabilities and novel actuation. Two significant limitations are multi-axis, three-dimensional motion of soft bodies alongside actuator dynamics and constraints, both of which are present in shape-memory-alloy (SMA)-powered soft robots. This article addresses both c...

This work introduces and presents a comprehensive study on a series of biphasic liquid metal (LM) composites that benefit from high conductivity, excellent stretchability, a low gauge-factor, excellent adhesion to a wide range of substrates, for sinter-free writing complex stretchable circuits. These trinary material systems are composed of a block...

Modeling the dynamics of soft robot limbs with electrothermal actuators is generally challenging due to thermal and mechanical hysteresis and the complex physical interactions that can arise during robot operation. This article proposes a neural network based on long short-term memory (LSTM) to address these challenges in actuator modeling. A plana...

We introduce a new electrode architecture for Dielectric Elastomer Actuators (DEAs) in which a soft polyacrylate film is coated with a biphasic mixture of silver, indium, and gallium. This Ag‐In‐Ga coating functions as a soft electrode that is ultrathin, highly compliant, highly conductive, stretchable, and non‐smearing. Compared to carbon grease,...

Soft sensors have continued growing interest in robotics, due to their ability to enable both passive conformal contact from the material properties and active contact data from the sensor properties. However, the same properties of conformal contact result in faster deterioration of soft sensors and larger variations in their response characterist...

Materials that can assist with perception and responsivity of an engineered machine are said to promote physical intelligence. Physical intelligence may be important for flexible and soft materials that will be used in applications like soft robotics, wearable computers, and healthcare. These applications require stimuli responsivity, sensing, and...

Control of soft robotic manipulators remains a challenge for designs with advanced capabilities and novel actuation. Two significant limitations are multi-axis, three-dimensional motion of soft bodies alongside actuator dynamics and constraints, both of which are present in shape-memory-alloy (SMA)-powered soft robots. This article addresses both c...

Liquid metal embedded elastomers (LMEEs) have attracted interest from researchers on account of their combination of low elastic modulus, high flexibility, and tunable electrical and/or thermal conductivity. One interesting feature of LMEEs is that their electrical resistance remains constant when stretched, which is desirable in many real-world ap...

Shape memory alloys (SMAs) are popular as actuators for use in soft robots due to their high work density and compatibility with miniaturized on-board batteries and power electronics. However, because SMA actuators are activated through electrical Joule heating, they exhibit poor energy efficiency and low actuator frequencies that arise from long c...