Robots fabricated with soft materials can provide higher flexibility and thus better safety while interacting in unpredictable situations. However, the usage of soft material makes it challenging to predict the deformation of a continuum body under actuation and therefore brings difficulty to the kinematic control of its movement. In this paper, we present a geometry-based framework for computing the deformation of soft robots within the range of linear material elasticity. After formulating both manipulators and actuators as geometry elements, deformation can be efficiently computed by solving a constrained optimization problem. Because of its efficiency, forward and inverse kinematics for soft manipulators can be solved by an iterative algorithm with low computational cost. Meanwhile, components with multiple materials can also be geometrically modeled in our framework with the help of a simple calibration. Numerical and physical experimental tests are conducted on soft manipulators driven by different actuators with large deformation to demonstrate the performance of our approach.

Robots fabricated by soft materials can provide higher flexibility and thus better safety while interacting with natural objects with low stiffness such as food and human beings. However, as many more degrees of freedom are introduced, the motion simulation of a soft robot becomes cumbersome, especially when large deformations are presented. Moreover, when the actuation is defined by geometry variation, it is not easy to obtain the exact loads and material properties to be used in the conventional methods of deformation simulation. In this paper, we present a direct approach to take the geometric actuation as input and compute the deformed shape of soft robots by numerical optimization using a geometry-based algorithm. By a simple calibration, the properties of multiple materials can be modeled geometrically in the framework. Numerical and experimental tests have been conducted to demonstrate the performance of our approach on both cabledriven and pneumatic actuators in soft robotics.

Purpose The purpose of this paper is to introduce a novel technique for printing with multiple materials using the DLP method. Digital-light-processing (DLP) printing uses a digital projector to selectively cure a full layer of resin using a mask image. One of the challenges with DLP printing is the difficulty of incorporating multiple materials within the same part. As the part is cured within a liquid basin, resin switching introduces issues of cross-contamination and significantly increased print time. Design/methodology/approach The material handling challenges are investigated and addressed by taking inspiration from automated storage and retrieval systems and using an active cleaning solution. The material tower is a compact design to facilitate the storage and retrieval of different materials during the printing process. A spray mechanism is used for actively cleaning excess resin from the part between material changes. Findings Challenges encountered within the multi-material DLP technology are addressed and the experimental prototype validates the proposed solution. The system has a cleaning effectiveness of over 90 per cent in 15 s with the build area of 72 inches, in contrast to the previous work of 50 per cent cleaning effectiveness in 2 min with only 6 inches build area. The method can also hold more materials than the previous work. Originality/value The techniques from automated storage and retrieval system is applied to develop a storage system so that the time complexity of swapping is reduced from linear to constant. The whole system is sustainable and scalable by using a spraying mechanism. The design of the printer is modular and highly customizable, and the material waste for build materials and cleaning solution is minimized.

The simulation of complex geometries and non-linear deformation has been a challenge for standard simulation methods. There has traditionally been a trade-off between performance and accuracy. With the popularity of additive manufacturing and the new design space it enables, the challenges are even more prevalent. Additionally, multiple additive manufacturing techniques now allow hyperelastic materials as raw material for fabrication and multi-material capabilities. This allows designers more freedom but also introduces new challenges for control and simulation of the printed parts. In this paper, a novel approach to implementing non-linear material capabilities is devised with negligible additional computations for geometry-based methods. Material curves are fitted with a polynomial expression, which can determine the tangent modulus, or stiffness, of a material based on strain energy. The moduli of all elements are compared to determine relative shape factors used to establish an element's blended shape. This process is done dynamically to update a material's stiffness in real-time, for any number of materials, regardless of linear or non-linear material curves.

Digital light processing (DLP) three-dimensional (3D) printing is a type of stereolithography (SLA) process that uses a digital projector to selectively cure resin according to a mask image. Each exposure solidifies a planar component of the printed part, allowing full layers to be cured at once. The DLP approach produces better quality parts at a faster rate compared to other 3D printing methods. One of the challenges with DLP printing is the difficulty of incorporating multiple materials within the same part. As the part is cured within a liquid basin, resin switching introduces issues of cross-contamination, layer height variability, and significantly increased print times. In this paper, a novel technique for printing with multiple materials using the DLP method is introduced. The material handling challenges are addressed with the design of a material swapping mechanism, a material tower, and an active part cleaning system. The material tower is a compact design to facilitate the storage and retrieval of different materials during the printing process. A spray mechanism is used for cleaning excess resin from the part between material changes. Challenges encountered within the 3D printing research community are addressed, with a focus on improving the shortcomings of modern multi-material DLP printers.