NOVELTY - Biofuel cell (10) for extraction of electricity from a biological system comprises an anode (11), comprising a first catalyst, where catalyst oxidizes a reducing agent, and delivers electrons onto a conducting matrix of the anode, the anode having an anode surface in contact with the reducing agent; and a cathode (12), comprising a second catalyst, where catalyst reduces an oxidizing agent and delivers electrons from the cathode, the cathode having a cathode surface in contact with the oxidizing agent.    USE - The biofuel cell is useful for extraction of electricity from biological system (claimed).    ADVANTAGE - The invention provides improved biofuel cell and device that provides increased flexibility, cost-effectiveness, environmental friendliness and/or ease of use.    DETAILED DESCRIPTION - Biofuel cell (10) for extraction of electricity from a biological system comprises an anode (11), comprising a first catalyst, where catalyst oxidizes a reducing agent, and delivers electrons onto a conducting matrix of the anode, the anode having an anode surface in contact with the reducing agent; and a cathode (12), comprising a second catalyst, where catalyst reduces an oxidizing agent and delivers electrons from the cathode, the cathode having a cathode surface in contact with the oxidizing agent; the anode (11) and cathode (12) being operatively connected in an electrical circuit (13), the anode (11) and cathode (12) thus delivering an electrical current and electrical potential; where the material of the anode or the cathode or both electrodes, of the biofuel cell (10) is flexible with an elastic modulus in the range of 0.02 to 1 MPa and has a viscosity in the range 0.01 to 200 Pa-second. INDEPENDENT CLAIMS are:    (1) a device comprising the biofuel cell; a sensor array for measuring characteristics of the biological body or tissue which are be used for referencing of analytical data; and an actuator for indicating the result of the measurement, where the biofuel cell (10), sensor array and actuator being operatively connected and incorporated into a single unit, where the interface between the body of interest and the device is flexible with an elastic modulus in the range of 0.02 to 1 MPa and with a viscosity range from 0.01 to 200 Pa-second; and    (2) a method for manufacturing biofuel cell comprising preparing a colloidal dispersion of self assembling molecules, with colloidal or multimolecular structures for controlling oxygen permeability and viscoelasticity of the biofuel cell electrodes; destabilizing the colloidal dispersion to induce a collapse of the same, thus inducing self assembly of the self assembling molecules; and letting the self assembling molecules assemble for 2 to 24 hours, resulting in a 3D structure.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of biofuel cell.    Biofuel cell (10)    Anode (11)    Cathode (12)    Electrical circuit (13)