Passive and wireless, implantable glucose sensing with phenylboronic acid hydrogel-interlayer RF resonators

Microelectronics‐Free, Augmented Telemetry from Body‐Worn Passive Wireless Sensors

“…The sensor node is an LRC resonator whose resonant frequency is sensitive to a chemical (e.g., glucose concentration, pH) or physical stimuli such as pressure and temperature through the material‐under‐test (MUT). Our group has been using “smart”‐material integrated split‐ring resonators (sensor‐SRRs) as multifunctional sensing resonators, [ 10,14,15 ] and thus we use similar structures in this study. Such constructs are composed of SRR structures whose capacitance is coupled to the behavior of designer environmentally responsive materials (most commonly as the interlayer of the SRR, Figure 1a bottom): this may include a glucose‐responsive hydrogel, biopolymer, compliant materials, or more.…”

“…Such constructs are rendered sensitive to environmental signals when one or more of the above circuit elements modulates with the perturbation of physical [ 7–9 ] or chemical stimuli. [ 10–12 ] For example, a coupled piezoresistive element will make the resonator sensitive to strain, [ 13 ] whereas coupled “smart” dielectric materials can make the resonant frequency of the resonator shift with chemical signals such as hydrogen ions or glucose. [ 10,14,15 ] The spectral response of a coupled LRC resonant structure is monitored remotely via inductive coupling to a readout coil connected to a vector network analyzer (VNA).…”

“…[ 10–12 ] For example, a coupled piezoresistive element will make the resonator sensitive to strain, [ 13 ] whereas coupled “smart” dielectric materials can make the resonant frequency of the resonator shift with chemical signals such as hydrogen ions or glucose. [ 10,14,15 ] The spectral response of a coupled LRC resonant structure is monitored remotely via inductive coupling to a readout coil connected to a vector network analyzer (VNA). [ 8,16–18 ] This capability is what lends the passive and wireless nature of such sensors, and a significant advantage of these constructs is that no microelectronics is required at the sensing node to form a fully operating sensing system.…”

“…This is generally limited to a few millimeters in many sensors as in passive radiofrequency identification (RFID) enabled [ 4 ] and parity‐time symmetry induced displacement sensors [ 19,20 ] to ensure the wireless link works reliably and that there is a strong magnitude response induced by the sensor in the readout coils. [ 8,10,14,21,22 ] Enhancing and improving the range of sensor readout has long been a challenge in passive wireless biosensing systems. Ideally, sensor response could be measured from longer ranges: this would improve the ease of sensor measurement, and relax constraints on where the sensor and readout nodes must be placed in relation to each other.…”

Paint‐On Epidermal Electronics for On‐Demand Sensors and Circuits

“…Emphasis has been placed on making sensors and electronics more conformal, stretchable, and low-profile for improved wearability and ambulatory considerations. [1,2] As a result, wearable electronics are evolving to be increasingly epidermal-like by modulating the sensor thickness and material stiffness to maximize moldability to skin roughness. [3] However, the current embryonic developmental stage of such technology and inherently complex manufacturing processes limit it to pre-determined configurations and applications.…”