Wearable System with Integrated Passive Microfluidics for Real-Time Electrolyte Sensing in Human Sweat

Wearable systems embodied as patches could offer noninvasive and real-time solutions for monitoring of biomarkers in human sweat as an alternative to blood testing, with applications in personalized and preventive healthcare. Sweat is considered to be a biofluid of foremost interest for analysis due the numerous biomarkers it contains. Recent studies have demonstrated that the concentration of some of these biomarkers in sweat, such as the electrolytes studied in this work, can be directly correlated to their concentrations in blood, making sweat a trusted biofluid candidate for non-invasive diagnostics. Until now, the biggest impediment to onâbody sweat monitoring was the lack of technology to analyze sweat composition in realâtime and mainly to continuously collect it. The goal of this work was to develop the building blocks of such wearable system for sweat electrolyte monitoring, with main emphasis on the passive microfluidics, the integrated miniaturized quasi-reference electrode and the functionalization of the sensing devices. The basic sensor technology is formed by Ion Sensitive Field Effect Transistors (ISFET) realized in FinFET and ultra-thin body Silicon on Insulator technology. This thesis shows the development of a state-of-the-art microsystem that allows multisensing of pH, Na+, K+ electrolyte concentrations in sweat, with high selectivity and high sensitivities (â50 mV/dec for all electrolytes), in a wearable fashion. The microsystem comprises a biocompatible skin interface that collects even infinitesimal quantities of sweat (of the order of hundreds of picoliters to tenths of nanoliters), which the body produces in periods of low physical effort. One of the main achievements of this work is the integration of Ion Sensing Fully Depleted FETs and zero power consumption microfluidics, enabling low power (less than 50 nWatts/sensor) wearable biosensing. The thesis presents the needed technological processes and optimizations, together with their characterization, in order to achieve a Lab-On-Skin system

Ultra-Low Power Ion-Sensing Smart Platform for Noninvasive Healthcare Applications

The development of nanotechnologies, and the advent of micro/nano-sensors with novel functionalities integrated on flexible substrates, has opened the way to the development of wearable technology. Interest in wearable technology comes from the considerable potential of this technology to tackle long-term health monitoring and implementing preventive care strategies. In particular, we are interested in a non-invasive device for hydration monitoring. Dehydration, is correlated with the concentration of various ionic concentration reflected in sweat. Thus, sweat can be used for continuous noninvasive physiological monitoring. In this project, we are proposing to implement an ultra-low power sweat sensing system by achieving heterogeneous integration of: 1) a sensing device based on advanced computing technology, 2) a miniaturized on-chip Ag/AgCl reference electrode, and 3) a wafer-compatible passive microfluidics. The full process for fabrication of this chip is achieved by standard semiconductor fabrication procedures. The targeted results in the first stages of this project were to measure the pH of a liquid using a miniaturized reference electrode and the acquisition of liquid through an inlet and displacing the substance to an outlet through capillary forces

Heterogeneous Integration of Low Power pH FinFET sensors with Passive Capillary Microfluidics and miniaturized Ag/AgCl quasi-Reference Electrode

This work presents one of the first low power pH sensing microfluidic chip based on the heterogeneous integration of: (i) high-k FinFET sensors with liquid gate, (ii) miniaturized Ag/AgCl quasi-Reference Electrode and (iii) passive microfluidic. The integration of these three components provides a fully integrated and compact platform that could be exploited for ionic monitoring in biofluids for healthcare applications. We describe the full fabrication process for the microfluidic system with the embedded reference electrode. The electrical characterization of heterogeneously integrated pH FinFET sensor with the integrated reference electrode shows Id-Vg characteristics with subthreshold swing SS~141mV/dec, low Ioff current and ION/IOFF > 105. When applying a constant current operation scheme, a sensitivity of 8mV/pH of the output drain voltage is reported. Due to the biocompatibility of the selected materials and small size, the resulting microsystem-on-chip could be used as a noninvasive wearable sensor for continuous monitoring of pH in sweat

Low power analog frontend for ISFET sensor readout

A low power analog frontend (AFE) for Ion-Sensitive Field effect Transistor sensor readout presented. The AFE is demonstrated with off-the-shelf components. It includes a biasing circuit to an ISFET sensor, a noise rejecting current readout circuit, and a igma-delta analog to digital converter. The digital output can be interpreted by a simple counter to acquire the ion-concentration in a drop of liquid on top of the calibrated ISFET sensor. A PH sensing experiment is performed validate the AFE. Total power consumption is less than 40 μW with 1.8 V supply

Low power analog frontend for ISFET sensor readout

A low power analog frontend (AFE) for Ion-Sensitive Field effect Transistor sensor readout is presented. The AFE is demonstrated with off-the-shelf components. It includes a biasing circuit to bias an ISFET sensor, a noise rejecting current readout circuit, and a sigma-delta analog to digital converter. The digital output can be interpreted by a simple counter to acquire the ion-concentration in a drop of liquid on top of the calibrated ISFET sensor. A PH sensing experiment is performed to validate the AFE. Total power consumption is less than 40 µW with 1.8 V supply

Embedded Passive Nano-Liter Micropump For Sweat Collection And Analysis

This paper presents a method to integrate biocompatible passive microfluidic systems within a sensing platform to allow continuous analysis of sweat in a wearable microsystem. The technology is promising for miniaturization of systems to enable access to biochemical information at the surface of human skin. The microfluidics are originally designed to work with ultra-low volumes of liquid to enable sweat analysis at any physiological situation (during intense physical activity or when at rest). Flow rates vary from 10s to 100s of pico-liters per second which can be adjusted by design. Capillary forces are used to move the liquid inside the microchannels in order to avoid power consumption. The SU8-based process is compatible with standard semiconductor techniques making it scalable, and suitable for integration with different sensing technologies. In this work, the microfluidic devices have been designed and integrated on top of ISFET devices

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans—anteaters, sloths, and armadillos—have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, 10 anteaters, and 6 sloths. Our data set includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the southern United States, Mexico, and Caribbean countries at the northern portion of the Neotropics, to the austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n = 5,941), and Cyclopes sp. have the fewest (n = 240). The armadillo species with the most data is Dasypus novemcinctus (n = 11,588), and the fewest data are recorded for Calyptophractus retusus (n = 33). With regard to sloth species, Bradypus variegatus has the most records (n = 962), and Bradypus pygmaeus has the fewest (n = 12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other data sets of Neotropical Series that will become available very soon (i.e., Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans data set. Please cite this data paper when using its data in publications. We also request that researchers and teachers inform us of how they are using these data