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Image source: Tesla.

Coating System and Method for E-Coating and Degasification of E-Coat Fluid During E-Coat

Owner: Tesla Inc.

Authors: Gunjan Agarwal, Sundaresan Avudaiappan, Christopher Lilywhite

Patent Issuer and Number: US P0902-2NWO


• Developed innovative solution to address critical Model-3 production ramp bottleneck by enhancing quality of anti-corrosion film deposited on vehicle during vehicle manufacturing paint application process; Scope of invention outside regular job responsibility.

• Set-up experiments to prove concept on pilot scale in a mini-lab next to production line; Achieved drastic cycle time reduction in process for production vehicles. Technique never implemented previously in automotive industry.

News and Media

My work on computational mechanical modeling for soft robotic systems and assistive wearable devices received international coverage in several news articles included below.

Journal Publications

Select publications are included below. For a comprehensive list of publications, please see CV

Design and Computational Modeling of a Modular, Compliant Robotic Assembly for Human Lumbar Unit and Spinal Cord Assistance

Gunjan Agarwal, Matthew Robertson, Harshal Sonar and Jamie Paik

Scientific Reports, Oct. 2017

DOI: 10.1038/s41598-017-14220-3


Abstract: Wearable soft robotic systems are enabling safer human-robot interaction and are proving to be instrumental for biomedical rehabilitation. In this manuscript, we propose a novel, modular, wearable robotic device for human (lumbar) spine assistance that is developed using vacuum driven, soft pneumatic actuators (V-SPA). The actuators can handle large, repetitive loads efficiently under compression. Computational models to capture the complex non-linear mechanical behavior of individual actuator modules and the integrated assistive device are developed using the finite element method (FEM). The models presented can predict system behavior at large values of mechanical deformations and allow for rapid design iterations. It is shown that a single actuator module can be used to obtain a variety of different motion and force profiles and yield multiple degrees of freedom (DOF) depending on the module loading conditions, resulting in high system versatility and adaptability, and efficient replication of the targeted motion range for the human spinal cord. The efficacy of the finite element model is first validated for a single module using experimental results that include free displacement and blocked-forces. These results are then extended to encompass an extensive investigation of bio-mechanical performance requirements from the module assembly for the human spine-assistive device proposed.

Stretchable Materials for Robust Soft Actuators towards Assistive Wearable Devices

Gunjan Agarwal, Nicolas Besuchet, Basile Audergon and Jamie Paik

Scientific Reports, Sep. 2016



Abstract: Soft actuators made from elastomeric active materials can find widespread potential implementation in a variety of applications ranging from assistive wearable technologies targeted at biomedical rehabilitation or assistance with activities of daily living, bioinspired and biomimetic systems, to gripping and manipulating fragile objects, and adaptable locomotion. In this manuscript, we propose a novel two-component soft actuator design and design tool that produces actuators targeted towards these applications with enhanced mechanical performance and manufacturability. Our numerical models developed using the finite element method can predict the actuator behavior at large mechanical strains to allow efficient design iterations for system optimization. Based on two distinctive actuator prototypes’ (linear and bending actuators) experimental results that include free displacement and blocked-forces, we have validated the efficacy of the numerical models. The presented extensive investigation of mechanical performance for soft actuators with varying geometric parameters demonstrates the practical application of the design tool, and the robustness of the actuator hardware design, towards diverse soft robotic systems for a wide set of assistive wearable technologies, including replicating the motion of several parts of the human body.

Design and Analysis of a Soft Pneumatic Actuator with Origami Shell Reinforcement

Laura Paez, Gunjan Agarwal and Jamie Paik

Soft Robotics, Sep. 2016



Abstract: Soft pneumatic actuators (SPAs) are versatile robotic components enabling diverse and complex soft robot hardware design. However, due to inherent material characteristics exhibited by their primary constitutive material, silicone rubber, they often lack robustness and repeatability in performance. In this article, we present a novel SPA-based bending module design with shell reinforcement. The bidirectional soft actuator presented here is enveloped in a Yoshimura patterned origami shell, which acts as an additional protection layer covering the SPA while providing specific bending resilience throughout the actuator's range of motion. Mechanical tests are performed to characterize several shell folding patterns and their effect on the actuator performance. Details on design decisions and experimental results using the SPA with origami shell modules and performance analysis are presented; the performance of the bending module is significantly enhanced when reinforcement is provided by the shell. With the aid of the shell, the bending module is capable of sustaining higher inflation pressures, delivering larger blocked torques, and generating the targeted motion trajectory.

Modeling and Analysis for Thermal Management in GaN HEMTs using Microfluidic Cooling

Gunjan Agarwal, Thomas Kazior, Thomas Kenny and Dana Weinstein

ASME Journal of Electronic Packaging, Oct. 2016

DOI: 10.1115/1.4035064


Abstract: In this article, thermal management in GaN-based microelectronic devices is addressed using microfluidic cooling. Numerical modeling is done using Finite element analysis (FEA) and results for temperature distribution are presented for a system comprising multiple cooling channels underneath GaN high electron mobility transistors (HEMTs). The thermal stack modeled is compatible for heterogeneous integration with conventional silicon-based CMOS devices. Parametric studies for cooling performance are done over a range of geometric and flow factors to determine the optimal cooling configuration within the specified constraints. A power dissipation of 2-4 W/mm is modeled along each HEMT finger in the proposed configuration. The cooling arrangements modeled here hold promising potential for implementation in high performance radio-frequency (RF) systems for power amplifiers, transmission lines and other applications in defense and military.

Modeling, Design, and Development of Soft Pneumatic Actuators with Finite Element Method 

Philip Moseley, Juan Manuel Florez1, Harshal Arun Sonar, Gunjan Agarwal, William Curtin and Jamie Paik

Advanced Engineering Materials, Dec. 2015

DOI: 10.1002/adem.201500503


Abstract: This work presents a comprehensive open-source simulation and design tool for soft pneumatic actuators (SPAs) using finite element method, compatible and extensible to a diverse range of soft materials and design parameters. Thorough characterization of the hyperelastic and viscoelastic behavior is illustrated using a sample soft material (Ecoflex 00_30), and an appropriate material constitutive law. SPA performance (displacement and blocked-force) are simulated for two types of SPA and validated with experimental testing. Real-world case studies are presented in which SPA designs are iteratively optimized through simulation to meet specified performance criteria and geometric constraints.

Shape-Selective Assembly of Anisotropic, Deformable Microcomponents Using Bottom-Up Micromanufacturing

Gunjan Agarwal and Carol Livermore

Micromachines, 2016, Vol. 7, Issue 4, Page 68 



Abstract: A technique for shape-selective directed assembly of anisotropic, deformable, chemically-identical microcomponents onto patterned rigid templates based on shape and size differences is modeled and demonstrated. The assembly method not only controls the selective placement of the components, but also aligns the components with the assembly sites. Unlike the assembly of isotropic (spherical) microcomponents, in which only size differences can be used to discriminate among chemically-identical components to achieve selective placement, differences in both shape and size can enable selectivity in the assembly of anisotropic (non-spherical) microcomponents. The present selective directed assembly is driven by shape-matching to a microfabricated template to provide selectivity, uniform chemical surface functionalization to promote assembly, and megasonic excitation to prevent assembly into poorly shape-matched binding sites. A theoretical framework quantifies the predicted selectivity of this approach and predicts that it will be effective for many material combinations, including hydrogels and bio-compatible polymers. Experiments demonstrate successful directed assembly of cylindrical, hydrogel colloidal microcomponents with 26 μm mean diameter and 50 μm length into silicon templates patterned with hemicylindrical assembly sites. During the assembly, tapered microcomponents with 150 μm length and a nominal diameter of 26 μm that decreases along the components’ lengths were successfully excluded from hemicylindrical assembly sites. These results provide the first demonstration of selective directed assembly of non-spherical microcomponents by this approach. The assembly shows high local yields in agreement with theory.

Size-Selective, Biocompatible, Manufacturable Platform for Structuring Deformable Microsystems

Gunjan Agarwal, Amelia Servi, Carol Livermore

Lab on a Chip, 2014, Vol. 14, Issue 17, Pages 3385 - 3393

DOI: 10.1039/C4LC00470A


Abstract: Precise, size-selective assembly and sorting are demonstrated in a low-cost system using manufacturable, replicated polymer templates to guide the assembly. Surface interactions between microscale objects and an assembly template are combined with fluid forces to drive site-selective organization of objects onto the template. Although controlling the organization of deformable objects on deformable surfaces offers a key tool for biological applications, the deformability can potentially interfere with the process that drives size selectivity. Theoretical models of the polymer assembly system were created to predict when selectivity will fail in deformable systems and were validated by comparison with experiments. Selective template-driven assembly of polystyrene microspheres on PDMS templates replicated from silicon masters was carried out using templated assembly by selective removal (TASR), demonstrating the effectiveness of selective assembly with low-cost, manufacturable materials and processes. The assembly of polystyrene microcomponents on PDMS shows high assembly yields and effective selectivity, in agreement with models.

Chip-Based Size-Selective Sorting of Biological Cells using High Frequency Acoustic Excitation

Gunjan Agarwal, Carol Livermore

Lab on a Chip, 2011, Vol. 11, Issue 13, Pages 2204-2211

DOI: 10.1039/C1LC20050J


Abstract: This work presents the size-selective sorting of single biological cells using the assembly process known as templated assembly by selective removal (TASR). We have demonstrated experimentally, for the first time, the selective placement and sorting of single SF9 cells (clonal isolate derived from Spodoptera frugiperda (Fall Armyworm) IPLB-Sf21-AE cells) into patterned hemispherical sites on rigid assembly templates using TASR. Nearly 100% of the assembly sites on the template were filled with matching cells (with assembly density as high as 900 sites per mm2) within short time spans of 3 minutes. 3-D reconstruction of cell profiles and volume analysis of cells trapped inside assembly sites demonstrates that only those cells that match the assembly site precisely (within 0.5 μm) in size are assembled on the template. The assembly conditions are also compatible with the extension of TASR to mammalian cells. TASR-based size-selective structuring and sorting of biological systems represents a valuable tool with potential for implementation in biological applications such as cell sorting for medical research or diagnostics, templating for artificial tissue replication, or isolation of single cells for the study of biological or mechanical behavior.

Selective Self-Assembly of Polymer Structures using Templated Assembly by Selective Removal

Gunjan Agarwal, Amelia Servi, Feras Eid, Carol Livermore

Nanotechnology, IEEE Transactions on, 2011, Vol. 10, Issue 3, Pages 617 - 625

DOI: 10.1109/TNANO.2010.2058815


Abstract: This paper presents the first models and experimental demonstrations of the selective assembly of deformable polymer structures onto rigid assembly templates using templated assembly by selective removal (TASR). Polystyrene microspheres with 2 μm diameter were successfully assembled with nearly 100% assembly yield into assembly sites that are uniformly well-matched to the microspheres' size and shape. The experiments also demonstrated selective assembly of microspheres into well-matched assembly sites when both well-matched and poorly matched assembly sites were available. In order to identify the limits of the TASR process for assembly in deformable systems, an analytical model was created. This model assesses the applicability of TASR to different materials systems using Hertzian contact theory to identify the onset of plastic deformation in a loaded, deformable sphere on a surface of given geometry. Using this model, TASR's effectiveness was predicted to include many polymers on rigid substrates. Quantitative comparison of the deformable system assembly data obtained here with existing TASR models for nondeformable systems shows significant agreement.

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