Martin Hjort

• PhD
• PostDoc Position at Lund University

Free-standing nanowires can gain intracellular access without causing stress or apoptosis. Current approaches to generate nanowires focus on lithographic patterning and inorganic materials (Si, GaAs, Al2O3, etc.) while organic materials are less explored. Use of organic conductive polymers allows for the creation of soft mixed ion–electron conducti...

Free-standing nanowires can gain intracellular access without causing cellular stress or apoptosis. Current approaches to generate nanowires focus on lithographic patterning and inorganic materials (Si, GaAs, Al2O3, etc.) while organic materials are less explored. Use of organic conductive polymers allows for creation of soft mixed ion–electron con...

Bioelectronics holds great potential as therapeutics, but introducing conductive structures within the body poses great challenges. While implanted rigid and substrate‐bound electrodes often result in inflammation and scarring in vivo, they outperform the in situ‐formed, more biocompatible electrodes by providing superior control over electrode geo...

Without intervention, cardiac arrhythmias pose a risk of fatality. However, timely intervention can be challenging in environments where transporting a large, heavy defibrillator is impractical, or emergency surgery to implant cardiac stimulation devices is not feasible. Here, we introduce an injectable cardiac stimulator, a syringe loaded with a n...

Bioelectronics can potentially complement classical therapies in nonchronic treatments, such as immunotherapy and cancer. In addition to functionality, minimally invasive implantation methods and bioresorbable materials are central to nonchronic treatments. The latter avoids the need for surgical removal after disease relief. Self-organizing substr...

Diamond-Blackfan anemia is a rare genetic bone marrow failure disorder which is usually caused by mutations in ribosomal protein genes. In the present study, we generated a traceable RPS19-deficient cell model using CRISPR-Cas9 and homology-directed repair to investigate the therapeutic effects of a clinically applicable lentiviral vector at single...

Bioelectronics has the potential to complement classical therapies in nonchronic treatments, such as immunotherapy and cancer. In addition to functionality, minimally invasive implantation methods and bioresorbable materials are central to nonchronic treatments. The latter is to avoid the need for surgical removal after disease relief. Self-organiz...

Interfacing electronics with neural tissue is crucial for understanding complex biological functions, but conventional bioelectronics consist of rigid electrodes fundamentally incompatible with living systems. The difference between static solid-state electronics and dynamic biological matter makes seamless integration of the two challenging. To ad...

Achieving CRISPR Cas9-based manipulation of mitochondrial DNA (mtDNA) has been a long-standing goal and would be of great relevance for disease modeling and for clinical applications. In this project, we aimed to deliver Cas9 into the mitochondria of human cells and analyzed Cas9-induced mtDNA cleavage and measured the resulting mtDNA depletion wit...

Injectable bioelectronics could become an alternative or a complement to traditional drug treatments. To this end, a new self-doped p-type conducting PEDOT-S copolymer (A5) was synthesized. This copolymer formed highly water-dispersed nanoparticles and aggregated into a mixed ion-electron conducting hydrogel when injected into a tissue model. First...

Due to their stable fluorescence, biocompatibility, and amenability to functionalization, fluorescent nanodiamonds (FND) are promising materials for long term cell labeling and tracking. However, transporting them to the cytosol remains a major challenge, due to low internalization efficiencies and endosomal entrapment. Here, nanostraws in combinat...

Significance Primary stem cells are difficult to transfect, and their viability and function are impaired by traditional transfection methods. We show that nanostraws can be used to deliver RNA to primary human hematopoietic stem cells without any detectable negative effects. Nanostraw-treated cells show no alterations in gene expression and fully...

Cas9-mediated gene editing of hematopoietic stem cells (HSCs) has great potential for functional studies and gene therapies. Current gene delivery methods, such as viral transduction or electroporation face challenges in clinically relevant parameters, such as efficiency, cell function and viability. We show that nanostraws can be used as an altern...

Intracellular delivery of mRNA, DNA, and other large macromolecules into cells plays an essential role in an array of biological research and clinical therapies. However, current methods yield a wide variation in the amount of material delivered, as well as limitations on the cell types and cargoes possible. Here, we demonstrate quantitatively cont...

Heusler compounds are a ripe platform for discovery and manipulation of emergent properties in topological and magnetic heterostructures. In these applications, the surfaces and interfaces are critical to performance; however, little is known about the atomic-scale structure of Heusler surfaces and interfaces or why they reconstruct. Using a combin...

Self-assembled, atomic diffusion controlled growth of InN quantum dots was realized on the side facets of dislocation-free and c-oriented GaN nanowires having a hexagonal cross-section. The nanowires were synthesized by selective area metal organic vapor phase epitaxy. A 3 Å thick InN wetting layer was observed after growth, on top of which the InN...

Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor-oxide interface....

This roadmap outlines the role semiconductor-based materials play in understanding the complex biophysical dynamics at multiple length scales, as well as the design and implementation of next-generation electronic, optoelectronic, and mechanical devices for biointerfaces. The roadmap emphasizes the advantages of semiconductor building blocks in int...

As semiconductor electronics keep shrinking, functionality depends on individual atomic scale surface and interface features that may change as voltages are applied. In this work we demonstrate a novel device platform that allows scanning tunneling microscopy (STM) imaging with atomic scale resolution across a device simultaneously with full electr...

The perfect switching between crystal phases with different electronic structure in III-V nanowires allows for the design of superstructures with quantum wells only a single atomic layer wide. However, it has only been indirectly inferred how the electronic structure will vary down to the smallest possible crystal segments. We use low-temperature s...

We study the surface diffusion and alloying of Sb into GaAs nanowires (NWs) with controlled axial stacking of wurtzite (Wz) and zinc blende (Zb) crystal phases. Using atomically resolved scanning tunneling microscopy, we find that Sb preferentially incorporates into the surface layer of the {110}-terminated Zb segments rather than the {112 ̅0}-term...

Significance Cell content analysis has rapidly become one of the most important new tools for measuring cell phenotype and behavior. However, the central limitation of current sampling technologies is they are destructive and must lyse the cells to measure the contents. This destruction prevents knowledge of prior or future states of the cell, whic...

We image GaP nanowires (NWs) incubated with human laminin, serum albumin (HSA), and blood plasma, using both cryo-transmission electron microscopy and synchrotron based x-ray photoemission electron microscopy. This extensive imaging methodology simultaneously shows structural, chemical and morphological details of the individual nanowire and the ad...

We present a study of InAs/InSb heterostructured nanowires by x-ray photoemission spectroscopy (XPS), scanning tunneling microscopy (STM) and in-vacuum electrical measurements. Starting with pristine nanowires covered only by the native oxide formed through exposure to ambient air, we investigate the effect of atomic hydrogen cleaning on the surfac...

Using scanning tunneling microscopy, we evaluate the surface structure and morphology down to the atomic scale for micrometers along Au-free grown InAs nanowires (NWs) free from native oxide. We find that removal of the native oxide (which covers the NWs upon exposure to the ambient air) using atomic hydrogen does not alter the underlying step stru...

While shell growth engineering to the atomic scale is important for tailoring semiconductor nanowires with superior properties, a precise knowledge of the surface structure and morphology at different stages of this type of overgrowth has been lacking. We present a systematic scanning tunneling microscopy (STM) study of homoepitaxial shell growth o...

We determine the detailed differences in geometry and band structure between wurtzite (Wz) and zinc blende (Zb) InAs nanowire (NW) surfaces using scanning tunneling microscopy/spectroscopy and photoemission electron microscopy. By establishing unreconstructed and defect-free surface facets for both Wz and Zb, we can reliably measure differences bet...

Using Scanning Tunneling Microscopy and Spectroscopy (STM/S) we study the atomic scale geometry and electronic structure of GaAs nanowires exhibiting controlled axial stacking of wurtzite (Wz) and zinc blende (Zb) crystal segments. We find that the nonpolar low-index surfaces: {110}, {10-10}, and {11-20} are unreconstructed, unpinned, and without s...

The Half Heuslers are currently an attractive family of compounds for high temperature thermoelectrics research, and recently, there has been renewed interest since some of these compounds are proposed to be topological insulators. NiTiSn belongs to the family of 18 valence electron Half Heuslers that are predicted to be semiconducting, despite bei...

We report transport and electronic band structure measurements on epitaxial films of the Half Heusler compound CoTiSb. CoTiSb belongs to the family of Half Heuslers with 18 valence electrons per formula unit that are predicted to be semiconducting despite being composed of all metallic components. Here the CoTiSb films were grown by molecular beam...

Using both synchrotron-based photoemission electron microscopy/spectroscopy and scanning tunneling microscopy/spectroscopy, we obtain a complete picture of the surface composition, morphology, and electronic structure of InP nanowires. Characterization is done at all relevant length scales from micrometer to nanometer. We investigate nanowire surfa...

The influence of InAs orientations and high-k oxide deposition conditions on the electrical and structural quality of Au/W/Al2O3/InAs metal-oxide-semiconductor capacitors was investigated using capacitance-voltage (C-V) and x-ray photoemission spectroscopy techniques. The results suggest that the interface traps around the conduction band edge are...

Mirror electron microscopy (MEM) imaging of InAs nanowires is a non-destructive electron microscopy technique where the electrons are reflected via an applied electric field before they reach the specimen surface. However strong caustic features are observed that can be non-intuitive and difficult to relate to nanowire geometry and composition. Uti...

InP nanowires (NWs) with differently doped segments were studied with nanoscale resolution using synchrotron based photoemission electron microscopy. We clearly resolved axially stacked n-type and undoped segments of the NWs without the need of additional processing or contacting. The lengths and relative doping levels of different NW segments as w...

Vertical InAs nanowires (NWs) wrapped by a thin high-kappa dielectric layer may be a key to the next generation of high-speed metal-oxide-semiconductor devices. Here, we have investigated the structure and chemical composition of the interface between InAs NWs and 2 nm thick Al2O3 and HfO2 films. The native oxide on the NWs is significantly reduced...

We present a synchrotron-based XPS investigation on the interface between InAs and Al2O3 or HfO2 layers, deposited by ALD at different temperatures, for InAs substrates with different surface orientations as well as for InAs nanowires. We reveal the composition of the native Oxide and how the high-kappa layer deposition reduces Oxide components. We...

Thin high-κ oxide films on InAs, formed by atomic layer deposition, are the key to achieve high-speed metal-oxide-semiconductor devices. We have studied the native oxide and the interface between InAs and 2 nm thick Al2O3 or HfO2 layers using synchrotron x-ray photoemission spectroscopy. Both films lead to a strong oxide reduction, obtaining less t...