A Glucose Fuel Cell for Implantable Brain–Machine Interfaces

We have developed an implantable fuel cell that generates power through glucose oxidation, producing steady-state power and up to peak power. The fuel cell is manufactured using a novel approach, employing semiconductor fabrication techniques, and is therefore well suited for manufacture together with integrated circuits on a single silicon wafer. Thus, it can help enable implantable microelectronic systems with long-lifetime power sources that harvest energy from their surrounds. The fuel reactions are mediated by robust, solid state catalysts. Glucose is oxidized at the nanostructured surface of an activated platinum anode. Oxygen is reduced to water at the surface of a self-assembled network of single-walled carbon nanotubes, embedded in a Nafion film that forms the cathode and is exposed to the biological environment. The catalytic electrodes are separated by a Nafion membrane. The availability of fuel cell reactants, oxygen and glucose, only as a mixture in the physiologic environment, has traditionally posed a design challenge: Net current production requires oxidation and reduction to occur separately and selectively at the anode and cathode, respectively, to prevent electrochemical short circuits. Our fuel cell is configured in a half-open geometry that shields the anode while exposing the cathode, resulting in an oxygen gradient that strongly favors oxygen reduction at the cathode. Glucose reaches the shielded anode by diffusing through the nanotube mesh, which does not catalyze glucose oxidation, and the Nafion layers, which are permeable to small neutral and cationic species. We demonstrate computationally that the natural recirculation of cerebrospinal fluid around the human brain theoretically permits glucose energy harvesting at a rate on the order of at least 1 mW with no adverse physiologic effects. Low-power brain–machine interfaces can thus potentially benefit from having their implanted units powered or recharged by glucose fuel cells

Dysfunctional Elimination Syndrome: Is It Related to Urinary Tract Infection or Vesicoureteral Reflux Diagnosed Early in Life?

Objective. It has been suggested that urinary tract infections (UTIs) early in life predispose to dysfunctional elimination syndrome (DES). This study evaluated the relationship between early UTI, vesicoureteral reflux (VUR), and DES by comparing two cohorts of school-aged children. Methods. The UTI cohort (n = 123) included children previously enrolled in a prospective treatment trial conducted between 1992 and 1997. All were diagnosed with a febrile UTI before 2 years of age. The comparison cohort (n = 125) included children who were evaluated for fever in the emergency department between 1992 and 1997, whose urine culture was negative. Dysfunctional elimination symptoms were compared in the two cohorts by having families complete a revised version of the Dysfunctional Voiding Scoring System. Results. Completed questionnaires were received from 248 children. There were no significant differences in selected demographic or clinical characteristics between the two cohorts. DES was present in 22% and 21% of children with and without a history of early UTI, respectively. Among children with UTIs, 18% of those with VUR and 25% of those without VUR had DES. Conclusions. Dysfunctional elimination is common in a general pediatric population. Neither UTI nor VUR diagnosed before 2 years of age was associated with DES in school-aged children