Release Date
August 23rd, 2023
Open Date
September 20th, 2023
Due Date(s)
October 18th, 2023
Close Date
October 18th, 2023
Topic No.


Development of an Exoskeleton Assistive Device that Augments Grip Strength for Seamless Mission Integration and Use in Military Casualty Transport Environment Scenarios


Department of DefenseN/A


Type: STTRPhase: Phase IYear: 2023


The Department of Defense (DoD) is seeking proposals for the development of an exoskeleton assistive device that augments grip strength for seamless mission integration and use in military casualty transport environment scenarios. The objective is to develop, demonstrate, and deliver an exoskeleton device that enhances grip strength while using a litter in a military medical casualty transport environment without interfering with other mission requirements or medical transport device/equipment design and operation. The exoskeleton should be adjustable, durable, and easily integrated into the medical mission, while also allowing for the continuation of patient evaluations and typical medical procedures. The project will be conducted in two phases. Phase I involves developing device concepts and designs, performing a technical trade assessment, and delivering documentation on the two most promising concept designs. Phase II includes evaluating and refining the prototype design, delivering functional prototypes, and conducting human volunteer research to demonstrate the effectiveness of the exoskeleton in litter transport scenarios. The successful device will have applications in military casualty evacuation, search and rescue operations, and various industrial and commercial fields. The solicitation is currently closed, and more information can be found on the DoD SBIR website.



OBJECTIVE: Develop, demonstrate, and deliver an exoskeleton device that augments grip strength while using a litter in a military medical casualty transport environment without interfering in other mission requirements or medical transport device/equipment design and operation.

DESCRIPTION: Litter transport is a standard on-foot procedure for initial casualty evacuation from the point of injury to the tactical evacuation zone and at times the only mode of transportation to move the injured person. Using a litter is physically demanding for Service Members (SMs). During the evacuation, the litter team may be required to provide critical medical care while actively engaging in combat to protect themselves and the patient. A straightforward approach to the dilemma of litter bearer fatigue and injury is to develop a medical assistive device that lessens the physical demands on the litter bearer. Using an assistive device (e.g., exoskeleton) during litter transport could decrease fatigue and increase the litter bearer’s ability to carry the litter, provide critical medical care, and sustain SM tasks.

Recently published recommendations by Madison (2022) are essential considerations for the development of a successful exoskeleton devices to maintain grip strength and dexterity of the SMs during dismounted litter load carriage tasks. Currently there are other available exoskeleton devices available for use however they do not meet the field medicine design requirements to specifically address grip strength augmentation while simultaneously allowing for dynamic movement over long distances. Designers should consider a possible solution to develop a quasi-passive, multi-joint, upper extremity exoskeleton for the medical user. The presence of a lower extremity exoskeleton would be beneficial to a litter bearer; however, grip strength is the first component to fatigue to exhaustion. This exhaustive state is why upper extremity exoskeletons take priority, but both can be beneficial to the SM. Thus, if lower extremity is included at any time during the design process, upper extremities must also be incorporated to assist with grip strength augmentation. Designers should consider using a combination of lighter actuators, such as pneumatic actuators or series elastic actuators, and passive actuators, such as springs or dampers. Combining these types of actuators may allow the exoskeleton to be lighter and consume less energy than if electric or hydraulic actuators were used. The use of passive actuators could also serve as a backup augmentation component if the exoskeleton runs on a limited power supply. The materials should be selected for durability in any terrain. The exoskeleton is required to withstand any environment in which they are employed and extreme temperatures (Crowell et al., 2019). Care must be taken to ensure the exoskeleton is adjustable to accommodate vast anthropometric variances among SMs. Exoskeletons should also easily be donned and doffed by the user to alleviate or reduce the possibility of improper fit (Gordon et al., 2014). The exoskeleton cannot require the litter team to surrender their weapons or remove body armor. The exoskeleton must not interfere with other current military medical equipment or weaponry (Crowell et al., 2019). The exoskeleton needs be easily integrated into the medical mission at hand and Army medics must also continue their care of the patient, which requires them to perform dexterity skills. For that reason, future exoskeletons must not interfere with patient evaluations, typical medical procedures, or any extra duties required of the SM (Blackbourne et al., 2012).

PHASE I: Develop device concepts and designs that address the desired capabilities and identified design requirements for an augmented grip strength exoskeleton to assist with casualty litter transport (Madison et al., 2022). Perform a technical trade assessment of the conceptual designs, to include improved combat performance following litter carry, a decrease in evacuation times, and decreasing the necessary four-person carry down to a two-person team. Work in Phase I should demonstrate the ability to integrate an exoskeleton device that augments grip strength during use in a military environment and during military litter transport without interfering in other mission capabilities. Additionally, work in Phase I should demonstrate the field compatibility of the design by delivering documentation on the two most promising concept designs, anticipated developmental testing requirements, proposed test procedures and preliminary data to demonstrate functionality and compatibility of major design elements, working principles, and use. The performer will establish a work plan for subsequent development and prototyping. Along with the concept designs, the performer shall deliver breadboard mock-ups to the sponsor.

PHASE II: Government representatives will evaluate the proposed mock-up exoskeleton for use in simulated and real-world litter transport scenarios and provide feedback to the performer for development of a refined design for use in further testing. Performers will improve upon the selected design and refine the prototype design for wear by SM by additional testing and design improvements. The performer will deliver 6 functional prototypes (or 3 pairs if prototypes are developed as a singular side or separated into a left and right side) for use in testing and evaluation. The exoskeleton needs to be adjustable to work cohesively with the vast anthropometric variances among SMs as well as current and future field medical transport equipment and devices (e.g., litter systems, etc.). The prototype will also include any hardware/software interfaces that are required for system functionality (e.g., external power, charging capabilities, data download and processing, etc.). The Government representatives will evaluate the exoskeleton against the identified design requirements and engage subject matter experts for feedback on device design and use. Device feedback will be delivered to the performer, who will use the provided feedback in conjunction with the performer’s identified deficiencies to refine the final design of the exoskeleton. After completion of the final design, 6 exoskeletons (or 3 pairs if design is developed as a singular side or separated into a left and right side) will be delivered along with design and validation testing documentation. The exoskeleton will be adjustable to work cohesively with the vast anthropometric variances among SMs. The final 6 prototypes (or 3 pairs as outlined above) will be evaluated in human volunteer research efforts to demonstrate their effectiveness in litter transport scenarios. The effects of the device on measures such as carry distance, grip strength, hand steadiness, marksmanship, and subjective user ratings will be evaluated.

PHASE III DUAL USE APPLICATIONS: A successful device will allow for litter bearers to transport casualties over greater distances with less fatigue, resulting in greater survivability for the Warfighter. Future and possible customers for a medical use exoskeleton intended to augment grip-strength are organizations with Search and Rescue responsibilities. Additionally, the device will be capable of integration with current and future-fielded civilian and military medical equipment/devices. Such organizations include local and State level first responders and the Department of Homeland Security Federal Emergency Management Agency during structural collapse in urban environments, the United States Department of Interior and National Park Services for inland-wilderness incidences and the Air Force Rescue Coordination Center, Air Education and Training Command, the Civil Air Patrol, the United States Navy, and United States Marine Corps helicopter squadrons during aeronautical search and rescues.

In several occupational fields, manual material handling tasks are still prevalent. Engineering an assistive device is one way to deal with these physically demanding jobs. The most common physically demanding activities performed by U.S. Army soldiers were found to be carrying and lifting. Conducting these tasks can cause injury, according to qualitatively analyzed evidence. Injuries to the musculoskeletal system are thought to cost the US economy at least $7 billion and $50 billion annually, respectively. Thus the exoskeleton could also find use in a number of industrial and commercial applications such as load carriage, tool handling, and manufacturing.


  1. Blackbourne, L. H., Baer, D. G., Eastridge, B. J., Butler, F. K., Wenke, J. C., Hale, R. G., Kotwal, R. S., Brosch, L. R., Bebarta, V. S., Knudson, M. M., Ficke, J. R., Jenkins, D., & Holcomb, J. B. (2012). Military medical revolution: Military trauma system. Journal of Trauma and Acute Care Surgery, 73(6), S388–S394.
  2. Crowell, H. P., Park, J.-H., Haynes, C. A., Neugebauer, J. M., & Boynton, A. C. (2019). Design, evaluation, and research challenges relevant to exoskeletons and exosuits: A 26-year perspective from the U.S. Army Research Laboratory. IISE Transactions on Occupational Ergonomics and Human Factors, 7(3-4), 199–212.
  3. Gordon, C. C., Blackwell, C. L., Bradtmiller, B., Parham, J. L., Barrientos, P., Paquette, S. P., Corner, B. D., Carson, J. M., Venezia, J. C., Rockwell, B. M., Mucher, M., & Kristensen, S. (2014). 2012 anthropometric survey of us army personnel: Methods and summary statistics (Report No. NATICK/TR-15/007). Army Natick Soldier Research Development and Engineering Center MA.
  4. Madison, A. M., Chambers, T. T., Stewart, A. S., & Chancey, V. C. (2022, Sept.). Evaluation of Litter Carriage Performance and Post-Carry Fatigue Effects in Prolonged Combat Field Care Environments (Part 1): Preliminary Design Considerations, Specifications, and Recommendations for Exoskeleton Feasibility, Suitability, and Efficacy in Dismounted Military Casualty Transport Scenarios. (Report No. USAARL-TECH-FR--2022-43). U.S. Army Aeromedical Research Laboratory, Fort Rucker, AL.

KEYWORDS: Litter carry, Casualty transport, Exoskeleton, Grip strength, Military casualty evacuation, Tactical evacuation, Medical evacuation, Assistive devices