Here we report on an entirely new kind of bioelectronic device - a conventional biosupercapacitor, which is built from copper containing redox proteins. Prior to biodevice fabrication, detailed spectroelectrochemical studies of the protein, viz. Acidithiobacillus ferrooxidcats rusticyanin, in solution and in adsorbed state, were performed, including estimation of the redox potential of the T1 site (0.62 V vs. NHE), protein midpoint potential when adsorbed on a self-assembled monolayer (0.34 V vs. NHE), as well as biocapacitance of rusticyanin modified gold electrodes (115 mu F cm(-2)). The symmetrical biosupercapacitor based on two identical gold electrodes modified with rusticyanin is able to capacitively store electricity and deliver electric power accumulated mostly in the form of biopseudocapacitance, when charged and discharged externally. When charged during Just 5 s, the biosupercapacitor with a total capacitance of about 73 mu F cm(-2) provided a maximum of 4 mu A cm(-2) peak current at 0.40 V. The biodevice, which can be charged and discharged at least 50 times without a significant loss of ability to store electric energy, had a low leakage current below 50 nA cm(-2).

Portabel medicinteknisk utrustning framträder alltmer som en av de mest lovande metoderna för vårdövervakning och personlig behandling. Förebyggande vård och hantering av kroniska sjukdomar är resurskrävande och en överföring av det konventionella sjukhuscentrerade sjukvårdssystemet till ett individcentrerat vårdsystem skulle vara samhällsekonomiskt gynnsam. I ett sådant scenario representerar bärbara mätenheter en teknik för övervakning av patienter på ett icke-invasivt och lättanvänt sätt. Denna teknik har möjlighet att tillhandahålla långsiktiga hälsostatusövervakningar och förmedla realtidsdata som läkare kan analysera för att ge patienterna återkoppling utan att behöva träffa patienterna lika ofta. Dessutom är många utan kroniska sjukdomar också intresserade av att övervaka kroppens hälsotillstånd för att förhindra sjukdomar och uppnå en högre livskvalitet. Dagens bärbara enheter integrerar elektronik med låg strömförbrukning och trådlös teknik, s.k. ”low power wireless technology”, för att överföra information från enheten till en mottagare. Elektronik behöver tillförlitliga strömkällor för att säkerställa funktionen, och biologiska kraftkällor är särskilt lämpliga alternativ att använda i bärbara enheter, eftersom de har hög prestanda när de används under fysiologiska förhållanden. Olika biologiska kraftkällor har tillverkats och testats i denna avhandling. Materialen som används för att tillverka dem är transparenta och flexibla. Dessa två egenskaper bidrar starkt till användarvänligheten och ökar därmed benägenheten att använda sådana kraftkällor. De biologiska kraftkällorna omvandlar kemisk energi till elektrisk energi genom att oxidera glukos och reducera syre under förhållanden som liknar dem som föreligger i mänsklig tårvätska. Detta arbete bidrar till att öka kunskapen om flexibla, transparenta och nanostrukturerade material som används för tillverkning av biologiska kraftkällor.

The thesis is focused on biological electric power sources based on transparent and flexible nanostructured electrodes. The power generating part of these biodevices was decorated with different biomaterials electrically wired to transparent electrodes based on either thin gold films, or indium tin oxide. Planar electrodes were additionally nanostructured by applying different nanomaterials to the electrode surfaces (such as indium tin oxide nanoparticles, graphene, carbon nanotubes) or by using nanoimprint lithography to increase the real surface area and thus boost enzyme loading. Bilirubin oxidase was used a cathodic biocatalyst for oxygen electroreduction, whereas different biomaterials were exploited as anodic bioelements, viz. redox enzymes (cellobiose and glucose dehydrogenase, as well as glucose oxidases) and thylakoid membranes, for glucose electrooxidation and light harvesting, respectively. Charge-storing parts of biodevices were based on electroconducting polymers, e.g. poly(3,4-ethylenedioxythiophene), carbon nanotubes, graphene, and indium tin oxide nanoparticles. The bioelectrodes were characterised in detail electrochemically, and also using scanning electron microscopy and atomic force microscopy. Transparent, membrane-free enzymatic fuel cells, as well as chemical and solar biosupercapacitors were assembled and basic parameters of biodevices, viz. open-circuit voltages, power and charge density, as well as stability, were studied in continuous and pulse operating modes.

We present a transparent and flexible self-charging biosupercapacitor based on an optimised mediator- and membrane-free enzymatic glucose/oxygen biofuel cell. Indium tin oxide (ITO) nanoparticles were spray-coated on transparent conducting ITO supports resulting in a flocculent, porous and nanostructured electrode surface. By this, high capacitive currents caused by an increased electrochemical double layer as well as enhanced catalytic currents due to a higher number of immobilised enzyme molecules were obtained. After a chemical pretreatment with a silane derivative, bilirubin oxidase from Myrothecium verrucaria was immobilized onto the ITO nanostructured electrode surface under formation of a biocathode, while bioanodes were obtained by either immobilisation of cellobiose dehydrogenase from Corynascus thermophilus or soluble PQQ-dependent glucose dehydrogenase from Acinetobacter calcoaceticus. The latter showed a lower apparent K-M value for glucose conversion and higher catalytic currents at mu M glucose concentrations. Applying the optimised device as a biosupercapacitor in a discontinuous charge/discharge mode led to a generated power output of 0.030 mW/cm(2) at 50 mu M glucose, simulating the glucose concentration in human tears. This represents an enhancement by a factor of 350 compared to the power density obtained from the continuously operating biofuel cell with a maximum power output of 0.086 mu W/cm(2) under the same conditions. After 17 h of charging/discharging cycles a remarkable current enhancement was still measured. The entire device was transferred to flexible materials and applied for powering a flexible display showing its potential applicability as an intermittent power source in smart contact lenses.

This article reviews recent progress in the development of biosupercapacitors - supercapacitors fabricated using biological materials. In conventional biosupercapacitors the biomaterial serves as the pseudocapacitive component, while in self-charging biodevices the biocomponent also functions as the biocatalyst. The performance characteristics of biosupercapacitors are summarized and characterized in the perspective of the broader family of electric power devices, including biodevices. Self-charging biosupercapacitors show great promise in pulse-power delivery at the milliwatt level, typically greatly exceeding the capability of free-running bio-fuel and bio-solar cells. Thus, chemical biosupercapacitors might be suitable for powering a new generation of miniaturized electronic applications, including those intended for use in medical technology, while solar biodevices might be used as highly functional, but at the same time low-cost, environmentally friendly, and technically undemanding electric power sources.

Here we report on an entirely new kind of bioelectronic device - a solar biosupercapacitor, which is built from a dual-​feature photobioanode combined with a double-​function enzymic cathode. The self-​charging biodevice, based on transparent nanostructured indium tin oxide electrodes modified with biol. catalysts, i.e. thylakoid membranes and bilirubin oxidase, is able to capacitively store electricity produced by direct conversion of radiant energy into elec. energy. When self-​charged during 10 min, using ambient light only, the biosupercapacitor provided a max. of 6 mW m-​ 2 at 0.20 V.

We detail a mediator- and membrane-free enzymatic glucose/oxygen biofuel cell based on transparent and nanostructured conducting supports. Chemically modified indium tin oxide nanoparticle modified electrodes were used to substantially increase the active surface area without significantly compromising transparency. Two different procedures for surface nanostructuring were employed, viz. spray-coating and drop-coating. The spray-coated biodevice showed superior characteristics as compared to the drop-coated enzymatic fuel cell, as a result of the higher nanostructured surface area as confirmed by electrochemical characterisation, as well as scanning electron and atomic force microscopy. Subsequent chemical modification with silanes, followed by the immobilisation of either cellobiose dehydrogenase from Corynascus thermophiles or bilirubin oxidase from Myrothecium verrucaria, were performed to obtain the bioanodes and biocathodes, respectively. The optimised biodevice exhibited an OCV of 0.67 V and power output of up to 1.4 mu W/cm(2) at an operating voltage of 0.35 V. This is considered a significant step forward in the field of glucose/oxygen membrane- and mediator-free, transparent enzymatic fuel cells.

A potentially implantable biocathode with the function of charge accumulation based on a nanobiocomposite including multiwall carbon nanotubes, polyaniline, and bilirubin oxidase is developed. The regularities of the functioning of the obtained electrode are studied in air-​satd. phosphate buffer soln., pH 7.4 (PB)​, and also in phosphate buffer soln. contg. redox-​active blood components (BMB)​. The open circuit potential of the biocathode is 0.33 and 0.08 V vs. the SCE in PB and BMB, resp.; it is completely restored after at least three self-​charge​/discharge cycles with connection to resistors with different resistance. Bioelectrocatalytic c.d. of oxygen redn. is 0.50 and 0.42 mA cm-​2 with the residual activity of 78 and 60​% of the initial value after 12 h of continuous operation in PB at 25°C and in BMB at 37°C, resp.

A review. This work provides an overview of the recent advances in the field of tear-​based wearable electrochem. biodevices, including non-​invasive biosensors, biol. fuel cells and biosupercapacitors. Contact lenses are attractive platforms for fabricating non-​invasive self-​contained gadgets for different applications, starting from devices with casual or mundane purposes only, like personalized smart lenses with direct (invisible for others) displays, and ending with biomedical devices for continuous fitness status and​/or health care monitoring. Key requirements and challenges that confront researchers in this exciting area are discussed.

Here the authors detail an optimized transparent capacitive glucose oxidizing bioanode, capable of supplying current densities of 10 μA cm-​2 at applied potentials of 0.1 V-​0.2 V vs. SCE, when continuously performing in a simple phosphate buffer, pH 7.4 and artificial human tears, both with a glucose concn. of 0.05 mM only. When operating in pulse mode, the bioanode was able to deliver current densities ≤21 μA cm-​2 at the beginning of the pulse with 571 μC cm-​2 total charges stored. The biogenic part of the enzymic device was a recombinant glucose oxidase mutant from Penicillium amagasakiense with high catalytic efficiency towards glucose, up to 14.5x104 M-​1 s-​1. The nonbiogenic part of the anodic system was based on a poly(3,​4-​ethylenedioxythiophene)​-​graphene nanocomposite, as a highly capacitive component with a capacitance d. in the 1 mF cm-​2 range, multi-​walled carbon nanotubes, as an addnl. nanostructuring element, and a conductive org. complex, as an electron shuttle between the redox enzyme and the electrode surface. The bioanode could potentially serve as a prototype of a double-​function enzymic anode for hybrid elec. power biodevices, energizing smart contact lenses.

We have developed and synthesized nanobiocomposite materials based on graphene, poly(3,4-ethylenedioxythiophene), and glucose oxidase immobilized on the surface of various nanomaterials (gold nanoparticles and multi-walled carbon nanotubes) of different sizes (carbon nanotubes of different diameters). Comparative studies of the possible influence of the nanomaterial’s nature on the bioelectrocatalytic characteristics of glucose-oxidizing bioanodes in a neutral phosphate buffer solution demonstrated that the bioelectrocatalytic current densities of nanocomposite-based bioanodes are only weakly dependent on the size of the nanomaterial and are primarily defined by its nature. The developed nanobiocomposites are promising materials for new bioelectronic devices due to the ease in adjusting their capacitive and bioelectrocatalytic characteristics, which allows one to use them for the production of dual-function electrodes: i.e., electrodes which are capable of generating and storing electric power simultaneously.