Epidermal Photonic Systems and Methods

Abstract

The invention provides systems and methods for tissue-mounted photonics. Devices of some embodiments implement photonic sensing and actuation in flexible and/stretchable device architectures compatible with achieving long term, mechanically robust conformal integration with a range of tissue classes, including in vivo biometric sensing for internal and external tissues. Tissue-mounted photonic systems of some embodiments include colorimetric, fluorometric and/or spectroscopic photonics sensors provided in pixelated array formats on soft, elastomeric substrates to achieve spatially and/or or temporally resolved sensing of tissue and/or environmental properties, while minimize adverse physical effects to the tissue. Tissue-mounted photonic systems of some embodiments enable flexible passive or active optical sensing modalities, including sensing compatible with optical readout using a mobile electronic devices such as a mobile phone or tablet computer.

1 - 69 . (canceled) 
     
     
         70 . An epidermal microfluidic sweat patch comprising:
 a flexible or stretchable substrate;   a microfluidic channel disposed in said flexible or stretchable substrate, the microfluidic channel having an inlet on a bottom surface of the flexible or stretchable substrate configured to receive sweat released by skin sweat glands;   a cavity disposed in said flexible or stretchable substrate, wherein the cavity is fluidically connected to the inlet or the microfluidic channel for receiving sweat released by skin sweat glands; and   a plurality of colorimetric indicators disposed in the microfluidic channel and/or in the cavity for multiparametric detection of a plurality of sweat parameters.   
     
     
         71 . The epidermal microfluidic sweat patch of  claim 70 , wherein said plurality of sweat parameters are two or more sweat parameters selected from the group consisting of:
 sweat volume and/or sweat rate;   sweat pH;   glucose concentration;   lactate concentration;   chloride concentration;   creatinine concentration;   copper ion concentration;   iron ion concentration and   ethanol concentration.   
     
     
         72 . The epidermal microfluidic sweat patch of  claim 70 , wherein at least one of the colorimetric indicators is configured to determine a sweat parameter as a function of time. 
     
     
         73 . The epidermal microfluidic sweat patch of  claim 72 , wherein the at least one sweat parameter as a function of time comprises sweat volume or sweat rate. 
     
     
         74 . The epidermal microfluidic sweat patch of  claim 73 , wherein the at least one colorimetric indicator that determines the sweat volume or sweat rate as a function of time is disposed in the microfluidic channel to provide an optically detectable sweat fluid leading edge in the microfluidic channel whose position can vary as a function of time. 
     
     
         75 . The epidermal microfluidic sweat patch of  claim 70 , comprising a plurality of detection reservoirs each fluidically connected to the microfluidic channel, wherein each detection reservoir contains a unique colorimetric indicator. 
     
     
         76 . The epidermal microfluidic sweat patch of  claim 75 , comprising four detection reservoirs for detecting four unique sweat parameters. 
     
     
         77 . The epidermal microfluidic sweat patch of  claim 70 , wherein the stretchable or flexible substrate comprises polydimethysiloxane (PDMS) having a net bending stiffness selected such that the epidermal microfluidic sweat patch is capable of establishing conformal contact with an epidermal surface. 
     
     
         78 . The epidermal microfluidic sweat patch of  claim 70 , wherein the stretchable or flexible substrate is selected to conformally contact an epidermal surface to provide a non-invasive daily-wear patch for personal healthcare monitoring. 
     
     
         79 . The epidermal microfluidic sweat patch of  claim 70 , wherein the microfluidic channel is part of a two-dimensional channel system within a PDMS substrate that directs a flow of sweat released from skin without pumps, valves or fluid detectors. 
     
     
         80 . The epidermal microfluidic sweat patch of  claim 79 , further comprising a plurality of detection reservoirs connected to the two-dimensional channel system. 
     
     
         81 . The epidermal microfluidic sweat patch of  claim 70 , wherein the microfluidic channel has a volume selected to accommodate a volume of sweat released from skin for a time period of up to 6 hours. 
     
     
         82 . The epidermal microfluidic sweat patch of  claim 81 , wherein the microfluidic channel comprises an orbicular outer circular or serpentine fluidic channel. 
     
     
         83 . The epidermal microfluidic sweat patch of  claim 70 , wherein the flexible or stretchable substrate comprises PDMS and has a total water loss that is less than 3% of sweat introduced to the microfluidic channel. 
     
     
         84 . The epidermal microfluidic sweat patch of  claim 70 , wherein one colorimetric indicator comprises cobalt (II) chloride in a hydrogel matrix coated on at least a portion of a surface of the microfluidic channel for determining sweat volume and sweat rate by optical detection of a color change in the microfluidic channel. 
     
     
         85 . The epidermal microfluidic sweat patch of  claim 84 , further comprising an additional colorimetric indicator disposed in the cavity for detection of a sweat biomarker, wherein the sweat biomarker is selected from the group consisting of: pH; glucose; lactate; chloride; copper ion; iron ion; and ethanol. 
     
     
         86 . The epidermal microfluidic sweat patch of  claim 70 , further comprising near field communication electronics supported by or embedded in the substrate for wireless communication with an external reader, including an external reader that is a smartphone, for quantitative determination of the plurality of sweat parameters. 
     
     
         87 . The epidermal microfluidic sweat patch of  claim 70 , further comprising an image process marker laminated on or disposed in the substrate for white balance and color calibration under various light conditions. 
     
     
         88 . The epidermal microfluidic sweat patch of  claim 70 , further comprising an adhesive positioned on the bottom surface of the flexible or stretchable substrate to adhere the epidermal microfluidic sweat patch to skin at an adhesion force between 1 N to 10 N. 
     
     
         89 . A method of measuring a plurality of sweat parameters, the method comprising the steps of:
 applying the epidermal microfluidic sweat patch of  claim 70  to a skin surface;   collecting sweat released from sweat glands in the microfluidic channel via the inlet;   introducing sweat to the cavity; and   detecting at least two optical changes in the epidermal microfluidic sweat patch by at least two colorimetric changes of at least two colorimetric indicators to thereby measure the plurality of sweat parameters.   
     
     
         90 . The method of  claim 89 , further comprising the step of monitoring at least one colorimetric change over time to determine a time course of at least one sweat parameter.