Microfluidic devices are provided for continuous sampling of biological fluid for extended periods of time, e.g. for periods of time up to and including 10 days. The microfluidic devices can be made from porous hydrophilic substrate, e.g. hydrophilic paper substrates. The devices can include a collection pad, an evaporative pump, and a channel connecting the collection pad and the evaporative pump. Hydrogels at the collection pad can promote collection of sweat or other biological fluids from a subject, which in some aspects is assisted by the use of one or more microneedles on the substrate. An evaporative pump can provide for long periods of sampling by providing continual pumping, e.g. through the use of an evaporation pad where sampled fluid can evaporate.

Biological chemicals, potentially found in blood are measured by collecting sweat and determining the concentration or meaning of the selected chemical in sweat. The sweat can be collected using a time based, interval collector 10 and analyzed using an external device. It can also be collected on a one time basis, using a flexible, chemical capacitor 50, or on a continuous basis using a chemical, field effect transducer 98.

A wearable body fat combustion measurement device includes a housing including a first chamber with an opening, a fixing means attached to the housing and configured to bring the housing into close contact with a user's skin in a state in which the opening of the first chamber faces the user's skin, a measurement sensor disposed inside the first chamber and configured to generate an electrical signal according to an amount of acetone contained in a gas evaporated from sweat discharged from the user's skin and introduced into the first chamber through the opening, a reference sensor disposed outside the first chamber and configured to generate an electrical signal according to a concentration of a gas component contained in an ambient air and detectable by the measurement sensor, and a signal processor configured to process the electrical signals received from the measurement sensor and the reference sensor.

Devices and methods for tuning biofluid sample pH to enable more accurate analyte concentration measurements with pH-sensitive biosensors. In the embodiments, biofluid samples react with a polymer buffering material during transfer to a sensing element. The reaction with the buffering material causes protonation or deprotonation of the sample based upon 1) the pH of the sample, and 2) the selected quantity and pKa of the functional groups in the buffering material. Controlling the H+ content of a biofluid sample has beneficial effects on the accuracy of the biosensor by reducing or eliminating signal changes due to redox moiety variability, thereby isolating signal changes reflecting analyte concentration.

Provided are microfluidic systems for monitoring a biofluid property and related methods. Specially configured microfluidic networks and associated structural support and functional elements, including flexible substrates, capping layers, and fluidic conduits and controllers, provide reliable biofluid collection. Optical components and indicators provide a reliable and readily observable readout, including of any of a number of biofluid properties, including directly from biofluid collected in the microfluidic network.

A head guard is provided. The head guard includes one or more sensors as part of an sensory input and communications system. The head guard wirelessly communicates data to remote computing devices for intelligent data collection.

The invention provides systems for handling biofluids including the transport, capture, collection, storage, sensing, and/or evaluation of biofluids released by tissue. Systems of some aspects provide a versatile platform for characterization of a broad range of physical and/or chemical biofluid attributes in real time and over clinically relevant timeframes. Systems of some aspects provide for collection and/or analysis of biofluids from conformal, watertight tissue interfaces over time intervals allowing for quantitative temporal and/or volumetric characterization of biofluid release, such as release rates and release volumes.

A method to determine medication adherence may include detecting whether a wearable electronic device is in use. The method may include detecting one or more markers in sweat vapor of the user using a chemical marker sensor of the wearable electronic device. The method may include, in response to detecting that the system is in use, determining whether the user has taken a therapeutic agent that includes the one or more markers based on detecting the one or more markers in the sweat vapor.

The disclosed invention provides a fluid sensing device capable of collecting a biofluid sample, such as interstitial fluid, blood, sweat, or saliva, concentrating the sample with respect to a target analyte, and measuring the target analyte in the concentrated sample. Embodiments of the invention can also determine the change in molarity of the fluid sample with respect to the target analyte, as the sample is concentrated by the device. Some embodiments of the disclosed invention provide a fluid sensing device comprising minimally invasive, microneedle-enabled extraction of interstitial fluid or other biofluid for continuous or prolonged on-body monitoring of biomarkers. Some embodiments allow the collection and measurement of analytes in of non-biological fluids, such as fuels, or bodies of water.

A wearable sensor system includes a flexible patch, an electronic circuit disposed on the flexible patch, and a disposable sensor disposed on the flexible patch and connected to the electronic circuit via a socket. The disposable sensor detects a chemical compound. The electronic circuit generates a detection signal commensurate with the chemical compound detected by the disposable sensor. The disposable sensor is removably plugged into the socket, thereby permitting replacement of the disposable sensor upon satisfaction of a predetermined condition. A battery disposed is on the flexible patch and connected to the electronic circuit to power the electronic circuit. A transceiver is connected to the electronic circuit, wherein the transceiver transmits the detection signal.