Roger Gabrielsson

Acido-basic control of the thermoelectric properties of poly(3,4-ethylenedioxythiophene)tosylate (PEDOT-Tos) thin films

PEDOT-Tos is one of the conducting polymers that displays the most promising thermoelectric properties.

Ionic thermoelectric supercapacitors

Temperature gradients are generated by the sun and a vast array of technologies and can induce molecular concentration gradients in solutions via thermodiffusion (Soret effect). For ions, this leads to a thermovoltage that is determined by the thermal gradient ΔT across the electrolyte, together with the ionic Seebeck coefficient αi. So far, redox-free electrolytes have been poorly explored in thermoelectric applications due to a lack of strategies to harvest the energy from the Soret effect. Here, we report the conversion of heat into stored charge via a remarkably strong ionic Soret effect in a polymeric electrolyte (Seebeck coefficients as high as αi = 10 mV K−1). The ionic thermoelectric supercapacitor (ITESC) is charged under a temperature gradient. After the temperature gradient is removed, the stored electrical energy can be delivered to an external circuit. This new means to harvest energy is particularly suitable for intermittent heat sources like the sun. We show that the stored electrical energy of the ITESC is proportional to (ΔTαi)2. The resulting ITESC can convert and store several thousand times more energy compared with a traditional thermoelectric generator connected in series with a supercapacitor.

Electronic polymers and DNA self-assembled in nanowire transistors.

Aqueous self-assembly of DNA and molecular electronic materials can lead to the creation of innumerable copies of identical devices, and inherently programmed complex nanocircuits. Here self-assembly of a water soluble and highly conducting polymer PEDOT-S with DNA in aqueous conditions is shown. Orientation and assembly of the conducting DNA/PEDOT-S complex into electrochemical DNA nanowire transistors is demonstrated.

Machine-Washable PEDOT:PSS Dyed Silk Yarns for Electronic Textiles

Durable, electrically conducting yarns are a critical component of electronic textiles (e-textiles). Here, such yarns with exceptional wear and wash resistance are realized through dyeing silk from the silkworm Bombyx mori with the conjugated polymer:polyelectrolyte complex PEDOT:PSS. A high Young’s modulus of approximately 2 GPa combined with a robust and scalable dyeing process results in up to 40 m long yarns that maintain their bulk electrical conductivity of approximately 14 S cm–1 when experiencing repeated bending stress as well as mechanical wear during sewing. Moreover, a high degree of ambient stability is paired with the ability to withstand both machine washing and dry cleaning. For the potential use for e-textile applications to be illustrated, an in-plane thermoelectric module that comprises 26 p-type legs is demonstrated by embroidery of dyed silk yarns onto a piece of felted wool fabric.

In vivo polymerization and manufacturing of wires and supercapacitors in plants

Significance Plants with integrated electronics, e-Plants, have been presented recently. Up to now the devices and circuits have been manufactured in localized regions of the plant due to limited distribution of the organic electronic material. Here we demonstrate the synthesis and application of a conjugated oligomer that can be delivered in every part of the vascular tissue of a plant and cross through the veins into the apoplast of leaves. The oligomer polymerizes in vivo due to the physicochemical environment of the plant. We demonstrate long-range conducting wires and supercapacitors along the stem. Our findings open pathways for autonomous energy systems, distributed electronics, and new e-Plant device concepts manufactured in living plants. Electronic plants, e-Plants, are an organic bioelectronic platform that allows electronic interfacing with plants. Recently we have demonstrated plants with augmented electronic functionality. Using the vascular system and organs of a plant, we manufactured organic electronic devices and circuits in vivo, leveraging the internal structure and physiology of the plant as the template, and an integral part of the devices. However, this electronic functionality was only achieved in localized regions, whereas new electronic materials that could be distributed to every part of the plant would provide versatility in device and circuit fabrication and create possibilities for new device concepts. Here we report the synthesis of such a conjugated oligomer that can be distributed and form longer oligomers and polymer in every part of the xylem vascular tissue of a Rosa floribunda cutting, forming long-range conducting wires. The plant’s structure acts as a physical template, whereas the plant’s biochemical response mechanism acts as the catalyst for polymerization. In addition, the oligomer can cross through the veins and enter the apoplastic space in the leaves. Finally, using the plant’s natural architecture we manufacture supercapacitors along the stem. Our results are preludes to autonomous energy systems integrated within plants and distribute interconnected sensor–actuator systems for plant control and optimization.

Regulating plant physiology with organic electronics

Significance Hormones play a crucial role in the coordination of the physiological processes within and between the cells and tissues of plants. However, due to a lack of capable technologies, direct and dynamic interactions with plants’ hormone-signaling systems remains limited. Here, we demonstrate the use of an organic electronic device—the organic electronic ion pump—to deliver the plant hormone auxin to the living root tissues of Arabidopsis thaliana seedlings, inducing differential concentration gradients and modulating plant physiology. Electronically regulated transport of aromatic structures such as auxin in an organic electronic device was achieved by synthesis of a previously unidentified class of dendritic polyelectrolyte. Such bioelectronic technology opens the door for precise, electronically mediated control of a plant’s growth and development. The organic electronic ion pump (OEIP) provides flow-free and accurate delivery of small signaling compounds at high spatiotemporal resolution. To date, the application of OEIPs has been limited to delivery of nonaromatic molecules to mammalian systems, particularly for neuroscience applications. However, many long-standing questions in plant biology remain unanswered due to a lack of technology that precisely delivers plant hormones, based on cyclic alkanes or aromatic structures, to regulate plant physiology. Here, we report the employment of OEIPs for the delivery of the plant hormone auxin to induce differential concentration gradients and modulate plant physiology. We fabricated OEIP devices based on a synthesized dendritic polyelectrolyte that enables electrophoretic transport of aromatic substances. Delivery of auxin to transgenic Arabidopsis thaliana seedlings in vivo was monitored in real time via dynamic fluorescent auxin-response reporters and induced physiological responses in roots. Our results provide a starting point for technologies enabling direct, rapid, and dynamic electronic interaction with the biochemical regulation systems of plants.

Electronic control over detachment of a self-doped water-soluble conjugated polyelectrolyte.

Water-soluble conducting polymers are of interest to enable more versatile processing in aqueous media as well as to facilitate interactions with biomolecules. Here, we report a substituted poly(3,4-ethylenedioxythiophene) derivative (PEDOT-S:H) that is fully water-soluble and self-doped. When electrochemically oxidizing a PEDOT-S:H thin film, the film detaches from the underlying electrode. The oxidation of PEDOT-S:H starts with an initial phase of swelling followed by cracking before it finally disrupts into small flakes and detaches from the electrode. We investigated the detachment mechanism and found that parameters such as the size, charge, and concentration of ions in the electrolyte, the temperature, and also the pH influence the characteristics of detachment. When oxidizing PEDOT-S:H, the positively charged polymer backbone is balanced by anions from the electrolyte solution and also by the sulfonate groups on the side chains (more self-doping). From our experiments, we conclude that detachment of the PEDOT-S:H film upon oxidation occurs in part due to swelling caused by an inflow of solvated anions and associated water and in part due to chain rearrangements within the film, caused by more self-doping. We believe that PEDOT-S:H detachment can be of interest in a number of different applications, including addressed and active control of the release of materials such as biomolecules and cell cultures.

Highly Stable Conjugated Polyelectrolytes for Water-Based Hybrid Mode Electrochemical Transistors

Hydrophobic, self-doped conjugated polyelectrolytes (CPEs) are introduced as highly stable active materials for organic electrochemical transistors (OECTs). The hydrophobicity of CPEs renders films very stable in aqueous solutions. The devices operate at gate voltages around zero and show no signs of degradation when operated for 104 cycles under ambient conditions. These properties make the produced OECTs ideal devices for applications in bioelectronics.

General Observation of Photocatalytic Oxygen Reduction to Hydrogen Peroxide by Organic Semiconductor Thin Films and Colloidal Crystals

Low-cost semiconductor photocatalysts offer unique possibilities for industrial chemical transformations and energy conversion applications. We report that a range of organic semiconductors are capable of efficient photocatalytic oxygen reduction to H2O2 in aqueous conditions. These semiconductors, in the form of thin films, support a 2-electron/2-proton redox cycle involving photoreduction of dissolved O2 to H2O2, with the concurrent photooxidation of organic substrates: formate, oxalate, and phenol. Photochemical oxygen reduction is observed in a pH range from 2 to 12. In cases where valence band energy of the semiconductor is energetically high, autoxidation competes with oxidation of the donors, and thus turnover numbers are low. Materials with deeper valence band energies afford higher stability and also oxidation of H2O to O2. We found increased H2O2 evolution rate for surfactant-stabilized nanoparticles versus planar thin films. These results evidence that photochemical O2 reduction may be a widespread feature of organic semiconductors, and open potential avenues for organic semiconductors for catalytic applications.