NOVELTY - A biofuel cell device (B1) (501) comprises: a fuel manifold (515) having a face, and at least one cavity in the face defining a fuel reservoir (541), an inlet and an outlet; an anode assembly (545) comprising at least one bioanode positioned for contact with fuel fluid in the fuel reservoir; a cathode assembly (551) comprising at least one cathode positioned for flow of fuel fluid through the bioanode to the cathode; and a controller operatively connected to the anode assembly and the cathode assembly for controlling the output of electrical current from the biofuel cell device.    USE - For generating electrical current and for supplying electrical power to a load (claimed). Also useful in ink formulations. The immobilized enzyme particles can be used as catalyst for e.g. esterification reaction and degumming of oils; for degrading stains in laundry soil; in wastewater treatment to break down wastes in the stream; for converting corn to high fructose corn syrup; for detecting analyte; for purification of substances; in biosensors and in food processing, e.g. baking processes.    ADVANTAGE - The biofuel cell relies on biological molecules such as enzymes to carry out reaction. The immobilized enzymes provide excellent enzyme stability.    DETAILED DESCRIPTION - A biofuel cell device (B1) (501) comprises: a fuel manifold (515) having a face, and at least one cavity in the face defining a fuel reservoir (541), an inlet in fluid communication with the reservoir for flow of fuel fluid into the manifold to fill the reservoir and an outlet in fluid communication with the reservoir for flow of fuel fluid out of the manifold; an anode assembly (545) comprising at least one bioanode positioned for contact with fuel fluid in the fuel reservoir; a cathode assembly (551) comprising at least one cathode positioned for flow of fuel fluid through the bioanode to the cathode; and a controller operatively connected to the anode assembly and the cathode assembly for controlling the output of electrical current from the biofuel cell device. INDEPENDENT CLAIMS are included for the following:    (1) a biofuel cell device (B2) for supplying electrical power to a load, comprising: a fuel cell, or a number of fuel cells electrically connected in series; a controller operatively connected to the fuel cell for controlling an output of the fuel cell according to a specific operating mode; and a switch circuit situated between the fuel cell and the load, the switch circuit being responsive to the controller for alternately connecting the fuel cell to the load and disconnecting the fuel cell from the load according to the operating mode;    (2) a biofuel cell device (B3) for supplying electrical power to a load, comprising: a fuel cell; a controller operatively connected to the fuel cell for controlling an output of the fuel cell according to a specific operating mode; and a supplemental power circuit responsive to the controller for selectively connecting a supplemental power source to the output of the fuel cell and hence supplementing the electrical power supplied to the load by the biofuel cell device;    (3) electrically conditioning an output of at least one fuel cell of a biofuel cell device, the biofuel cell device being adapted for supplying electrical power to a load, the method involving: electrically connecting a switch circuit between the fuel cells and the load; and switching the switch circuit to selectively connect at least one of the fuel cells to the load according to at least one of operating modes;    (4) generating electricity using the biofuel cell device involving oxidizing the fuel fluid at the bioanode and reducing the oxidant at the cathode or biocathode;    (5) an electrode comprising: a first region of electrically conductive material being permeable to air and impermeable to a fuel fluid; a second region of conductive material being permeable to the fuel fluid and to air; and a non-precious metal catalyst being able to contact both the fuel fluid and air; where an air-breathing half-cell comprising the electrode would generate a current density of at least about 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or more mA/cm when operating at room temperature, an electrode potential of 0.4 V, and a catalyst loading of 10 mg/cm2;    (6) a heat-treated electrode comprising an electron conductor; and at least one non-precious metal catalyst being capable of selectively reducing oxygen to water;    (7) a catalyst comprising cobalt(II)1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine (CoPcF); and polypyrrole; where the CoPcF and polypyrrole have been heat treated to increase the interaction between the cobalt metal atom and the nitrogen atoms of the polypyrrole;    (8) an electrode comprising first region of electrically conductive material being permeable to air and impermeable to a fuel fluid; a second region of conductive material being substantially permeable to the fuel fluid and to air; and a catalyst being able to contact both the fuel fluid and air;    (9) a biocathode comprising: electron conductor; at least one cathode enzyme capable of reacting with an oxidant to produce water; and an enzyme immobilization material capable of immobilizing and stabilizing the enzyme, the material being permeable to the oxidant; where the electron conductor comprises functionalized multi-walled carbon nanotubes and/or an activated carbon-based material;    (10) a particle comprising a core coated with an immobilized enzyme, the enzyme being immobilized in an immobilization material and either having an activity of at least about 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or more relative to its initial activity before immobilization and coating, or retaining at least about 75% of its initial catalytic activity for at least 1, 2, 3, 4, 5, 6 or 7 days when the enzyme is continuously catalyzing a chemical transformation;    (11) a particle comprising a core coated with an immobilized organelle, the organelle being immobilized in an immobilization material;    (12) preparing (P1) particle coated with an immobilized enzyme or organelle; and    (13) self-supporting electron conductor comprising monolayer comprised of a first electrically conductive material having high surface area for transferring electrons, a second electrically conductive material for supporting the electron conductor, and a binder, where the weight ratio of the second electrically conductive material to the first electrically conductive material is at least 0.5: 1 to provide sufficient rigidity to the electron conductor for it to be self-supporting.    DESCRIPTION OF DRAWING(S) - The figure shows separated perspective of fuel cell device.    biofuel cell device (501)    fuel manifold (515)    fuel reservoir (541)    anode assembly (545)    cathode assembly. (551)