Robert F. Shepherd

Modern agricultural robotic systems are constrained by limited sensing and manipulation capabilities, particularly in fruit harvesting, where variability in color, size, and firmness poses significant challenges. Existing solutions, often reliant on rigid grippers and single-modality sensors, frequently cause fruit bruising and substantial postharvest losses. Here, we present a compact, five-finger soft robotic gripper with integrated multimodal sensing-including vision, tactile, and curvature sensing-for adaptive and non-destructive fruit harvesting. The system incorporates 13 sensors, onboard electronics, local computation, and a rotational harvesting module. Each finger embeds custom stretchable optical fibers that function as tactile and curvature sensors, while the palm houses a miniaturized camera and distance sensor. The gripper actuates within two seconds at 80 kPa, exerts up to 6 N of pulling force, and lifts objects up to 1 kg-more than 16 times its own weight. Its workspace expands from 200 mm² to 14,000 mm², enabling the handling of fruits with diverse shapes and sizes. Each finger bends up to 240°, with performance closely matching finite element predictions. For vision measurements, the hue channel in the HSV color space enables robust real-time color detection, achieving 100% shape classification accuracy and a size measurement error below 1.8%. Tactile sensors distinguish soft from firm objects, while curvature sensors accurately measure the finger's bending state-both based on optical signal loss. Real-time demonstrations validate the system's ability to assess ripeness using multimodal data (vision, tactile, and curvature) and successfully harvest greenhouse strawberries with minimal damage. This platform offers a versatile, sensor-rich solution for both precision agriculture and general-purpose robotic manipulation.

Imaging techniques are fundamental tools in biology for examining cell growth and responses to the environment. Many tissues require fixing, staining, and/or clearing before they can be visualized under a microscope. However, these protocols, such as those using propidium iodide (PI), a fluorescent cationic stain widely used across biological specimens including plant, mammalian, and bacterial, often require laborious dehydration and rehydration steps to facilitate stain penetration. These stepwise solvent exchanges, for example, by passing tissues through a graded ethanol series, are time-consuming and manually intensive. While automated tissue processors offer an alternative, they are outside of the budget for many labs. Here, we present an open-source, low-cost (~$400) automated tissue processor that performs sequential dehydration and rehydration of biological tissues, significantly reducing hands-on labor. The processor is made of readily available, standardized parts and includes custom software that allows users to define and save protocols. We demonstrate the use of the processor by automating a multi-day PI staining protocol across multiple plant species, tissue morphologies, and users, and by comparing tissue quality with hand-processed samples. Our design provides a low-cost, accessible alternative to expensive commercial tissue processors, offering a practical solution for a wide range of biology laboratories.

Fostering relationships between the disability and soft robotics communities will spark innovations that could benefit all.

ABSTRACT Volumetric Additive Manufacturing (VAM) offers unparalleled speed in creating arbitrary 3D geometries; primarily due to requiring only one degree of freedom (DoF), rotation. A limitation, however, has been its size scale (∼3 cm), which has been attributed to light absorption. Accordingly, efforts have focused on adding translational DoF's to expose more material volume to this light path. The additional translational DoF increases print times, and still has not yielded thicker parts in all axes. This paper focuses on an important challenge to printing arbitrarily thick sections in all axes, thermal evolution from photopolymerization. In this work, we describe a scientific investigation and engineering solution to this issue, along with improvements to remaining challenges by: (i) using the index matching fluid as an active cooling source, (ii) optimizing the resin for deeper light propagation, and (iii) implementing a 4k light engine and large lens for higher intensity projections. With this system, we were able to print at least 70,153 mm 3 part volumes at throughputs of ∼390 mm 3 s −1 . Our printing system produces parts ∼60% larger and ∼400% faster than the next largest VAM method, and ∼1,740% larger and ∼23% faster than the next fastest method.

High-resolution electronic tactile displays stand to transform haptics for remote machine operation, virtual reality, and digital information access for people who are blind or visually impaired. Yet, increasing the resolution of these displays requires increasing the number of individually addressable actuators while simultaneously reducing their total surface area, power consumption, and weight, challenges most evidently reflected in the dearth of affordable multiline braille displays. Blending principles from soft robotics, microfluidics, and nonlinear mechanics, we introduce a 10-dot-by-10-dot array of 2-millimeter-diameter, combustion-powered, eversible soft actuators that individually rise in 0.24 milliseconds to repeatably produce display patterns. Our rubber architecture is hermetically sealed and demonstrates resistance to liquid and dirt ingress. We demonstrate complete actuation cycles in an untethered tactile display prototype. Our platform technology extends the capabilities of tactile displays to environments that are inaccessible to traditional actuation modalities.

Precision agriculture aims to increase crop yield while reducing the use of harmful chemicals, such as pesticides and excess fertilizer, using minimal, tailored interventions. However, these strategies are limited by factors such as sensor quality, which typically relies on visual plant expression, and the manual, destructive nature of many nonvisual measurement methods, including the Scholander pressure bomb. By automating more intimate interactions with foliage in vivo, it would be possible to inject chemical and biological probes that reveal more phenotypes—such as water stress in response to varying environmental conditions and visible gene expression to measure the success of gene engineering applications. To address this, we developed a soft robotic leaf gripper and stamping-injection method to improve foliar delivery of nanoscale synthetic and biological probes. This allows for nondestructive, in situ, multispecies applications. We used two probes: Agrobacterium tumefaciens carrying the RUBY gene as a reporter system for plant transformation and nanoparticle hydrogels for measuring leaf water potential (ψ). Our hourglass-shaped design enabled the gripper to exert higher forces with reduced radial expansion compared with conventional designs, achieving an injection success rate above 91%. Studies on sunflower ( Helianthus annuus L.) and cotton ( Gossypium hirsutum L.) showed that our method achieved an average 12-fold increase in infiltration areas, with substantially less leaf damage—3.6% in sunflower and none in cotton—compared with the needle-free syringe method. Enabling long periods of successful in vivo phenotyping on both species after precise and safe foliar delivery underscores the potential of the leaf gripper for robotic plant bioengineering.

The ability to control the movement of charged species in the circuitry of living beings and machines is essential for complex signal processing, computation, and, ultimately, higher functionality. We describe a class of photo-ion generators (PIGs) based on non-ionic photoacids that can create large (> 1000x) irreversible changes in ionic conductivity under illumination depending on the PIG species, concentration, and solvent. Incorporation of PIGs into polyurethane rubber by simple swelling methods yields soft (E > 2 MPa), stretchable, photo-ionic gels (PIGels). The resolution of photo-patterned conductivity in PIGels is less than 1 cm and demonstrates stability over several days, suggesting utility in engineered devices. Utilizing this novel class of material, we demonstrate high sensitivity mechanical sensors via conductance changes ([ΔG/G0]/σ = 20 MPa-1) and photo-writable, soft circuitry.

Abstract The adaptable, modular structure of muscles, combined with their confluent energy storage allows for numerous architectures found in nature: trunks, tongues, and tentacles to name some more complex ones. To provide an artificial analog to this biological soft muscle, a self‐powered, soft hydrostat actuator is presented. As an example of how to use these modules, a worm robot is assembled where the near totality of the body stores electrochemical potential. The robot exhibits an extremely high system energy density (51.3 J g −1 ), using a redox flow battery motif, with a long theoretical operational range of more than 100 m on a single charge. The innovation lies in the battery pouch, fabricated with a dry‐adhesion method, automatically bonding Nafion separators to a silicone‐urethane copolymer body. These pouches contain anolyte within a hydrostat pod filled with catholyte, increasing current density per pod. Each pod has a motor and tendon actuator for radial compression and expansion. By linking these self‐contained pods in series, the robot worm is created that automatically navigates an enclosed, curved path. This high‐capacity soft worm also climbs up and down a vertical pipe, using a two‐anchor crawling gait, with an extra payload equivalent to 1.5 times its body weight.

The batteries that power untethered underwater vehicles (UUVs) serve a single purpose: to provide energy to electronics and motors; the more energy required, the bigger the robot must be to accommodate space for more energy storage. By choosing batteries composed primarily of liquid media [e.g., redox flow batteries (RFBs)], the increased weight can be better distributed for improved capacity with reduced inertial moment. Here, we formed an RFB into the shape of a jellyfish, using two redox chemistries and architectures: (i) a secondary ZnBr 2 battery and (ii) a hybrid primary/secondary ZnI 2 battery. A UUV was able to be powered solely by RFBs with increased volumetric ( Q ~ 11 ampere-hours per liter) and areal (108 milliampere-hours per square centimeter) energy density, resulting in a long operational lifetime ( T ~ 1.5 hours) for UUVs composed of primarily electrochemically energy-dense liquid (~90% of the robot’s weight).

Abstract This article describes the challenges of defining and classifying autonomous material systems. We believe that there is no consistent definition of “autonomy” across different scientific disciplines, and this difference makes it difficult to assess progress as a whole. The authors pose that there is a paradox between achieving greater autonomy and, presently, maintaining an achievable cost of material system complexity. Examples are given from the artificial and biological world and make the, somewhat safe, claim that organisms make a better tradeoff between the manufacturing complexity required to build autonomy. The authors draw from the Autonomous Driving System scale to classify autonomy levels in material systems, and give specific examples of increasing architectural complexity. We then call out specific research trajectories to pursue in order to make better tradeoffs in this engineering contradiction, manufacturing being a specific example. This article will hopefully bring some uniformity between different materials science disciplines. Graphical abstract

Living tissues are still far from being used as practical components in biohybrid robots because of limitations in life span, sensitivity to environmental factors, and stringent culture procedures. Here, we introduce fungal mycelia as an easy-to-use and robust living component in biohybrid robots. We constructed two biohybrid robots that use the electrophysiological activity of living mycelia to control their artificial actuators. The mycelia sense their environment and issue action potential-like spiking voltages as control signals to the motors and valves of the robots that we designed and built. The paper highlights two key innovations: first, a vibration- and electromagnetic interference-shielded mycelium electrical interface that allows for stable, long-term electrophysiological bioelectric recordings during untethered, mobile operation; second, a control architecture for robots inspired by neural central pattern generators, incorporating rhythmic patterns of positive and negative spikes from the living mycelia. We used these signals to control a walking soft robot as well as a wheeled hard one. We also demonstrated the use of mycelia to respond to environmental cues by using ultraviolet light stimulation to augment the robots' gaits.

Computed Axial Lithography (CAL) is an emerging technology for manufacturing complex parts, all at once, by circumventing the traditional layered approach using tomography. Overprinting, a unique additive manufacturing capability of CAL, allows for a 3D geometry to be formed around a prepositioned insert where the occlusion of light is compensated for by the other angular projections. This method opens the door for novel applications within additive manufacturing for multi-material systems such as endoskeletal robots. Herein, this work presents one such application with a simple Gelatin Methacrylate (GelMA)hydrogel osmotic actuator with an embedded endoskeletal system. GelMA is an ideal material for this application as it is swellable and has reversible thermal gelation, enabling suspension of the endoskeleton during printing. By tuning the material formulation, the actuator design, and post-processing, swelling-induced bending actuation of 60 degrees is achieved. To aid in the printing process, a simple computational method for determining the absolute dose absorbed by the resin allowing for print time prediction is also proposed.

Two of the main challenges in origami antenna designs are creating a reliable hinge and achieving precise actuation for optimal electromagnetic (EM) performance. Herein, a waterbomb origami ring antenna is introduced, integrating the waterbomb origami principle, 3D‐printed liquid metal (LM) hinges, and robotic shape morphing. The approach, combining 3D printing, robotic actuation, and innovative antenna design, enables various origami folding patterns, enhancing both portability and EM performance. This antenna's functionality has been successfully demonstrated, displaying its communication capabilities with another antenna and its ability to navigate narrow spaces on a remote‐controlled wheel robot. The 3D‐printed LM hinge exhibits low DC resistance (200 ± 1.6 mΩ) at both flat and folded state, and, with robotic control, the antenna achieves less than 1° folding angle accuracy and a 66% folding area ratio. The antenna operates in two modes at 2.08 and 2.4 GHz, ideal for fixed mobile use and radiolocation. Through extensive simulations and experiments, the antenna is evaluated in both flat and folded states, focusing on resonant frequency, gain patterns, and hinge connectivity. The findings confirm that the waterbomb origami ring antenna consistently maintains EM performance during folding and unfolding, with stable resonant frequencies and gain patterns, proving the antenna's reliability and adaptability for use in portable and mobile devices.

Traditional methods for wireless power transfer (WPT) in wearable devices have mainly utilized the Inductive Power Transfer (IPT) and the Magnetic Resonant Coupling (MRC) methods. IPT demonstrates very high efficiencies when operating at short distances (typically 1 cm to 3 cm). However, its efficiency significantly diminishes when operates at distances beyond the 3 cm mark, decaying at a rate of 1/r 6 , which makes it impractical for longer-range WPT applications. In contrast

Anand Kumar Mishra, Zhihong Nie, Jamie Paik and Robert Shepherd introduce the Soft Matter themed issue on Soft Robotics.

Insects perform feats of strength and endurance that belie their small stature. Insect-scale robots-although subject to the same scaling laws-demonstrate reduced performance because existing microactuator technologies are driven by low-energy density power sources and produce small forces and/or displacements. The use of high-energy density chemical fuels to power small, soft actuators represents a possible solution. We demonstrate a 325-milligram soft combustion microactuator that can achieve displacements of 140%, operate at frequencies >100 hertz, and generate forces >9.5 newtons. With these actuators, we powered an insect-scale quadrupedal robot, which demonstrated a variety of gait patterns, directional control, and a payload capacity 22 times its body weight. These features enabled locomotion through uneven terrain and over obstacles.

Triply periodic minimal surface lattices have mechanical properties that derive from the unit cell geometry and the base material. Through computation software like nTopology and Abaqus, these geometries are used to tune nonlinear stress–strain curves not readily achievable with solid materials alone and to change the compliance by two orders of magnitude compared to the constituent material. In this study, four elastomeric TPMS gyroids undergo large deformation compression and tension testing to investigate the impact of the structure's geometry on the mechanical properties. Among all the samples, the modulus at strain ε varies by over one order of magnitude (7.7–293.4 kPa from FEA under compression). These lattices are promising candidates for designing multifunctional systems that can perform multiple tasks simultaneously by leveraging the geometry's large surface area to volume ratio. For example, the architectural functionality of the lattice to bear loads and store mechanical energy along with the larger surface area for energy storage is combined. A compliant double‐gyroid capacitor that can simultaneously achieve three functions is demonstrated: load bearing, energy storage, and sensing.

As an alternative approach to ionic data transmission with hydrogel as substrate, this work explores the possible applications of liquid electrolyte filling cavity of a stretchable, flexible elastomeric tubing, which is the primary ingredient used in redox flow battery systems. While hydrogel-based ionic impedance characterization and its data communication capability have been well studied, the multifunctional use of redox flow battery electrolyte for data communication, in addition to powering, is novel, especially in the context of soft robotics. This work also describes a simple signal conditioning technique that addresses the signal decaying problem due to long-distance ionic data transmission. Finally, we describe the prototypical design of a decentralized data communication between two, or possibly more, systems of power and control. This work presents the concept of a decentralized control of a robot's hydraulic actuation system, that will allow for the system's functional robustness in the event of one of the two, or possibly more, modules lose power or become severed from the robot's body.

Fluid-Driven Elastomer Actuators In article number 2200330, Kirstin H. Petersen and co-workers present fluidic actuators in which viscous fluids propagate in a scalable framework manifesting control of the structure by the structure, generating pressure distributions within each actuator - achieving interchangeable, spatio-temporal motions with a single inlet. Through theory and experiments, the article introduces the foundation of a design methodology, unlocking significantly more capable and competitive soft robots.

Herein, complex motion in soft, fluid‐driven actuators composed of elastomer bladders arranged around a neutral plane and connected by slender tubes is demonstrated. Rather than relying on complex feedback control or multiple inputs, the motion is generated with a single pressure input, leveraging viscous flows within the actuator to produce nonuniform pressure between bladders. Using an accurate predictive model coupling with a large deformation Cosserat rod model and low‐Reynolds‐number flow, all dominating dynamic interactions including extension and curvature are captured with two governing equations. Given insights from this model, five design elements are described and demonstrated in practice. By choosing the relative timescales between the solid, fluid, and input pressure cycles, the tip of the actuator can obtain almost any desired trajectory and can be placed anywhere temporarily within its 2D workspace. Finally, the benefits of viscous‐driven soft actuators are showcased in a six‐legged untethered robot able to walk 0.05 body lengths per second. The foundation is laid for a new class of morphologically intelligent, soft robotic actuators that enables complex deformations and multifunctionality without explicit drivers; whereby generating nonuniform pressure distributions, their infinite degrees of freedom can be exploited.

Aeronautics research has continually sought to achieve the adaptability and morphing performance of avian wings, but in practice, wings of all scales continue to use the same hinged control-surface embodiment. Recent research into compliant and bio-inspired mechanisms for morphing wings and control surfaces has indicated promising results, though often these are mechanically complex, or limited in the number of degrees-of-freedom (DOF) they can control. Seeking to improve on these limitations, we apply a new paradigm denoted Autonomous Material Composites to the design of avian-scale morphing wings. With this methodology, we reduce the need for complex actuation and mechanisms, and allow for three-dimensional placement of stretchable fiber optic strain gauges (Optical Lace) throughout the metamaterial structure. This structure centers around elastomeric conformal lattices, and by applying functionally-graded warping and thickening to this lattice, we allow for local tailoring of the compliance properties to fit the desired morphing. As a result, the wing achieves high-deformation morphing in three DOF: twist, camber, and extension/compression, with these morphed shapes effectively modifying the aerodynamic performance of the wing, as demonstrated in low-Reynolds wind tunnel testing. Our sensors also successfully demonstrate differentiable trends across all degrees of morphing, enabling the future state estimation and control of this wing.