Julian Jepsen

Metal hydrides are known as a potential efficient, low-risk option for high-density hydrogen storage since the late 1970s. In this paper, the present status and the future perspectives of the use of metal hydrides for hydrogen storage are discussed. Since the early 1990s, interstitial metal hydrides are known as base materials for Ni – metal hydride rechargeable batteries. For hydrogen storage, metal hydride systems have been developed in the 2010s [1] for use in emergency or backup power units, i. e. for stationary applications. With the development and completion of the first submarines of the U212 A series by HDW (now Thyssen Krupp Marine Systems) in 2003 and its export class U214 in 2004, the use of metal hydrides for hydrogen storage in mobile applications has been established, with new application fields coming into focus. In the last decades, a huge number of new intermetallic and partially covalent hydrogen absorbing compounds has been identified and partly more, partly less extensively characterized. In addition, based on the thermodynamic properties of metal hydrides, this class of materials gives the opportunity to develop a new hydrogen compression technology. They allow the direct conversion from thermal energy into the compression of hydrogen gas without the need of any moving parts. Such compressors have been developed and are nowadays commercially available for pressures up to 200 bar. Metal hydride based compressors for higher pressures are under development. Moreover, storage systems consisting of the combination of metal hydrides and high-pressure vessels have been proposed as a realistic solution for on-board hydrogen storage on fuel cell vehicles. In the frame of the “Hydrogen Storage Systems for Mobile and Stationary Applications” Group in the International Energy Agency (IEA) Hydrogen Task 32 “Hydrogen-based energy storage”, different compounds have been and will be scaled-up in the near future and tested in the range of 500 g to several hundred kg for use in hydrogen storage applications.

Needle-based injections currently enable the administration of a wide range of biomacromolecule therapies across the body, including the gastrointestinal tract1–3, through recent developments in ingestible robotic devices4–7. However, needles generally require training, sharps management and disposal, and pose challenges for autonomous ingestible systems. Here, inspired by the jetting systems of cephalopods, we have developed and evaluated microjet delivery systems that can deliver jets in axial and radial directions into tissue, making them suitable for tubular and globular segments of the gastrointestinal tract. Furthermore, they are implemented in both tethered and ingestible formats, facilitating endoscopic applications or patient self-dosing. Our study identified suitable pressure and nozzle dimensions for different segments of the gastrointestinal tract and applied microjets in a variety of devices that support delivery across the various anatomic segments of the gastrointestinal tract. We characterized the ability of these systems to administer macromolecules, including insulin, a glucagon-like peptide-1 (GLP1) analogue and a small interfering RNA (siRNA) in large animal models, achieving exposure levels similar to those achieved with subcutaneous delivery. This research provides key insights into jetting design parameters for gastrointestinal administration, substantially broadening the possibilities for future endoscopic and ingestible drug delivery devices. Tethered or ingestible delivery systems that deliver liquid microjets in axial and radial directions can be used to deliver macromolecules to different parts of the gastrointestinal tract with good bioavailability.