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The emerging field of “Bioelectronics” seeks to exploit biology in conjunction with
electronics in a wider context encompassing, for example, biomaterials for information
processing, information storage, electronic components and actuators. Biomolecules and
biological cells as the building blocks of higher-level functional devices can, moreover, be
used for recognition or sensing within biosensors. Bioelectronics research also seeks to use
biomolecules to perform the electronic functions that semiconductor devices currently
perform. Research activities in both of the following general domains can be distinguished:
          Micro/Nano-electronics for Life-Sciences, i.e. how micro/nano electronic systems
          can help to solve important problems in life sciences. Examples include
          integrated devices for detection of cells, DNA, Proteins, and small molecules.
          Life-Sciences for micro/nano electronic systems, i.e. how we can learn from nature
          to build micro and nano electronic devices. Examples include protein mediated
          electronic devices and neuro-electronic circuitries.

   A key aspect is the interface between biological materials and electronics which
requires a highly interdisciplinary research, involving biologists, chemists, physicists,
materials scientists and engineers. Within this context, JARA-FIT works in the fields of both
molecule- and cell-based bioelectronics.

                                                                                                Figure 1: (a) Schematic of a crossbar
                                                                                                junction with a SAM of MUA and
                                                                                                immobilized cytochrome c. (b) AFM
                                                                                                image of an Au Crossbar junction,
                                                                                                electrode width: 200 nm and 500 nm 

     In molecular bioelectronics JARA-FIT focuses on research and development of
applications related to nanobiotechnology, biomolecular engineering, bioelectronic
devices and molecular miniaturization. Here the research centers around the observation of
charged entities at interfaces formed between the soft condensed or liquid phases of living
systems and the solid state world of metallic and/or semiconductor electrodes.
Fundamental studies embrace electron and ion transport phenomena, signaling and signal
transduction, and the associated molecular and organizational structures that control and
influence these in-living systems. In particular, we are interested in the development of
active bio-inorganic components for the understanding and control of the charge transport
in and across biomolecules. Promising biological, respectively, bio-inorganic hetero-
structures shall provide the basis for the development of conceptual electronic
components. Our approach to fabricate and assemble bio-inorganic electronic components
will permit to study chemical, physical, biological and electronic phenomena and processes
with high scalability down to the nanometer range.

                                    Figure 2: Neuronal
                                    cell grown on a field-
                                    effect transistor

A major challenge in bioelectronics is the patterning of functional components and the
interfacing with electrical components. One approach is to build Crossbar Arrays with
molecular interlayers. Commonly, Crossbar Arrays are fabricated by evaporation of the top
electrodes onto the assembled molecules. Defects in the molecular layer or the evaporation
process itself often led to direct filaments. These filaments represent short-cuts influencing
the properties of the junction. As an alternative, we have already demonstrated the
fabrication of Crossbar junctions with biomolecular interlayers by employing Soft
Lithography methods as nano-imprint, thereby avoiding short-cuts (Figure 1).
     In the past few years, substantial progress has been made in understanding the
interactions between cells and (electronic) substrates (Figure 2). For instance, extracellular
matrix proteins with nanostructured templates can be used to control the geometry of the
cell-chip interface. Monitoring the electrochemical activity of living cells with electronic
sensors represents an emerging technique ranging from basic research in neuroelectronics
to various fields of pharmacological analyses. The realization of this approach requires
several steps: (1) development and fabrication of electronic devices for the low noise
registration of cellular signals, (2) development and fabrication of electronic devices for the
stimulation of cells, and (3) the effective coupling between the cellular systems and the
electronic devices as well as the control over the cellular connections. Patterning
extracellular matrix proteins and structured surfaces enables the controlled and selective
adhesion and growth of cells onto chips, and the realization and investigation of cellular
networks of controlled complexity and geometry. They can be used to study the excitation
and transmission of signals in neuronal and genetically modified cells.
     In order to establish a two-way interface between a neuron and an electronic device,
JARA-FIT has followed several approaches in the past. On the one side, JARA-FIT focused on
the detection of extracellular neuronal signals with field-effect transistors (FET) and metal
microelectrode arrays (MEA). In order to study the signal transfer between cell and sensor
spot, we recorded signals from different cell types with non-metalized FETs or MEAs and
used classical patch-clamp measurements for comparison. The obtained signals can be
described in a first approximation by a simplified coupling model (Point Contact Model). On
the other side, we used either the MEAs or floating-gate FET structures for successful
extracellular stimulation of excitable cells.
     In the future, we are aiming at a large-scale integration of two-way cell-sensor
interfaces on-chip.


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Description: Bioelectronics is a biology and Electronic Information Science infiltrated each formed a new subject, the development of bio-electronics fully reflects the interdependence of the two disciplines and the relationship and mutual promotion. Bio-electronic research consists of two aspects: First, e-learning in biological systems, including electronic characteristic of biological molecules, biological systems of information storage and information transfer, thus the development of biological information processing based on the principle of new technology; 2 is the use of electronic information science theory and technology to solve biological problems, including access to biological information, biological information analysis, but also combined with the development of biomedical nanotechnology detection and adjuvant therapy techniques, development of micro-instrumentation.