Itthipon Jeerapan

Highly Stretchable Fully-Printed CNT-Based Electrochemical Sensors and Biofuel Cells: Combining Intrinsic and Design-Induced Stretchability

We present the first example of an all-printed, inexpensive, highly stretchable CNT-based electrochemical sensor and biofuel cell array. The synergistic effect of utilizing specially tailored screen printable stretchable inks that combine the attractive electrical and mechanical properties of CNTs with the elastomeric properties of polyurethane as a binder along with a judiciously designed free-standing serpentine pattern enables the printed device to possess two degrees of stretchability. Owing to these synergistic design and nanomaterial-based ink effects, the device withstands extremely large levels of strains (up to 500% strain) with negligible effect on its structural integrity and performance. This represents the highest stretchability offered by a printed device reported to date. Extensive electrochemical characterization of the printed device reveal that repeated stretching, torsional twisting, and indenting stress has negligible impact on its electrochemical properties. The wide-range applicability of this platform to realize highly stretchable CNT-based electrochemical sensors and biofuel cells has been demonstrated by fabricating and characterizing potentiometric ammonium sensor, amperometric enzyme-based glucose sensor, enzymatic glucose biofuel cell, and self-powered biosensor. Highly stretchable printable multianalyte sensor, multifuel biofuel cell, or any combination thereof can thus be realized using the printed CNT array. Such combination of intrinsically stretchable printed nanomaterial-based electrodes and strain-enduring design patterns holds considerable promise for creating an attractive class of inexpensive multifunctional, highly stretchable printed devices that satisfy the requirements of diverse healthcare and energy fields wherein resilience toward extreme mechanical deformations is mandatory.

A stretchable and screen-printed electrochemical sensor for glucose determination in human perspiration

Here we present two types of all-printable, highly stretchable, and inexpensive devices based on platinum (Pt)-decorated graphite for glucose determination in physiological fluids. Said devices are: a non-enzymatic sensor and an enzymatic biosensor, the latter showing promising results. Glucose has been quantified by measuring hydrogen peroxide (H2O2) reduction by chronoamperometry at -0.35V (vs pseudo-Ag/AgCl) using glucose oxidase immobilized on Pt-decorated graphite. The sensor performs well for the quantification of glucose in phosphate buffer solution (0.25M PBS, pH 7.0), with a linear range between 0 mM and 0.9mM, high sensitivity and selectivity, and a low limit of detection (LOD). Thus, it provides an alternative non-invasive and on-body quantification of glucose levels in human perspiration. This biosensor has been successfully applied on real human perspiration samples and results also show a significant correlation between glucose concentration in perspiration and glucose concentration in blood measured by a commercial glucose meter.

A Textile-Based Stretchable Multi-Ion Potentiometric Sensor

A textile-based wearable multi-ion potentiometric sensor array is described. The printed flexible sensors operate favorably under extreme mechanical strains (that reflect daily activity) while offering attractive real-time noninvasive monitoring of electrolytes such as sodium and potassium.

Noninvasive Transdermal Delivery System of Lidocaine Using an Acoustic Droplet-Vaporization Based Wearable Patch

Current technologies for managing acute and chronic pain have focused on reducing the time required for achieving high therapeutic efficiency. Herein a wearable transdermal patch is introduced, employing an acoustic droplet vaporization (ADV) methodology, as an effective noninvasive transdermal platform, for a fast local delivery of the anesthetic agent lidocaine. The skin-worn patch consists of a flexible drug reservoir containing hundreds of micropores loaded with lidocaine, and mixed with the perfluorocarbon (PFC) emulsion. The ultrasound-triggered vaporization of the PFC emulsion provides the necessary force to breach dermal barriers. The drug release kinetics of our model was investigated by measuring the amount of lidocaine that passed through phantom tissue and pigskin barriers. The ADV platform increases the payload skin penetration resulting in shorter treatment times compared to passive diffusion or ultrasound alone, holding considerable promise for addressing the delayed therapeutic action and slow pain relief of existing delivery protocols. It is envisioned that the integration of ADV-based transdermal devices could be expanded to the depth-dependent delivery of other pain management, vaccines, and gene therapy modalities.

Fully edible biofuel cells

The first example of a fully edible biofuel cell (BFC), based solely on highly biocompatible food materials without any additional external mediators, is described. The new BFC energy-harvesting approach relies on a variety of edible plant/mushroom extract/vegetable oil/charcoal paste biocatalytic electrodes and represents an attractive route for energy harvesting towards ingestible biomedical devices. The edible BFC anode and cathode paste materials consist of biocatalytic rich mushroom, apple, plum and banana plant tissues, along with dietary activated charcoal and water-immiscible olive oil, corn oil, and sesame oil for creating the paste matrix. The ethanol/O2 BFC relies on a bioanode, based on ethanol oxidation induced by the intrinsic biocatalytic activity of its mushroom component, along with a biocathode based on oxygen-reducing apple extract containing polyphenol-oxidase and phenolic compounds. The integrated natural catalytic system and selective biocatalytic activity of the natural extracts offer successful operation of BFCs without any extra mediators or membrane separating the anode and the cathode. The mushroom/apple/olive oil-based BFC displays a favorable power density of 282 μW cm-2 with an open circuit voltage (OCV) of 0.24 V. The power and OCV signals are linearly proportional to ethanol levels and indicate promise for self-powered alcohol sensing. The food-based BFCs were reproducible and able to maintain a power performance of over 80% of their initial output for four hours. These edible energy-harvesting BFCs hold great promise for the next-generation of ingestible devices and smart self-powered biosensors for monitoring health and the digestive system.

Sweat-based wearable energy harvesting-storage hybrid textile devices

This study demonstrates the first example of a stretchable and wearable textile-based hybrid supercapacitor–biofuel cell (SC–BFC) system. The hybrid device, screen-printed on both sides of the fabric, is designed to scavenge biochemical energy from the wearers sweat using the BFC module and to store it in the SC module for subsequent use. The BFC relies on lactate, which is oxidized enzymatically to generate electricity. The generated bioenergy is stored directly and rapidly in the printed in-plane SCs. The SC energy-storage module employs MnO2/carbon nanotube composites that offer high areal capacitance and cycling electrochemical stability. Both printed SC and BFC devices rely on optimal elastomer-containing ink formulations and serpentine structure patterns that impart a stable electrochemical performance after a variety of mechanical deformations. Such a fabrication route ensures that the energy-harvesting and storage properties of the two integrated devices are not compromised. The SC–BFC hybrid system can thus deliver stable output over long charging periods, boost the voltage output of the BFC, and exhibit favorable cycling ability. Such attractive performance, demonstrated in successful on-body testing, along with the unique architecture and low-cost scalable fabrication, make the new garment-ased hybrid energy device useful for meeting the power and mechanical resiliency requirements of wearable electronics and smart textiles.

Enzymatic glucose/oxygen biofuel cells: Use of oxygen-rich cathodes for operation under severe oxygen-deficit conditions

A glucose/oxygen biofuel cell (BFC) that can operate continuously under oxygen-free conditions is described. The oxygen-deficit limitations of metabolite/oxygen enzymatic BFCs have been addressed by using an oxygen-rich cathode binder material, polychlorotrifluoroethylene (PCTFE), which provides an internal oxygen supply for the BFC reduction reaction. This oxygen-rich cathode component mitigates the potential power loss in oxygen-free medium or during external oxygen fluctuations through internal supply of oxygen, while the bioanode employs glucose oxidase-mediated reactions. The internal oxygen supply leads to a prolonged energy-harvesting in oxygen-free solutions, e.g., maintaining over 90% and 70% of its initial power during 10- and 24-h operations, respectively, in the absence of oxygen. The new strategy holds considerable promise for energy-harvesting and self-powered biosensing applications in oxygen-deficient conditions.