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The development of power generators that can function in harsh snowy environments and in contact with snow can be beneficial but challenging to accomplish. Herein, we introduce the first snow-based triboelectric nanogenerator (snow-TENG) that can be used as an energy harvester and a multifunctional sensor based on the principle of snow-triboelectrification. In this work, we used a 3D printing technique for the precise design and deposition of the electrode and triboelectric layer, leading to flexible, stretchable and metal-free triboelectric generators. Based on the single electrode mode, the device can generate an instantaneous output power density as high as 0.2 mW/m(2), an open circuit voltage up to 8 V, and a current density of 40 μA/m(2). In addition, the snow-TENG can function as a miniaturized weather station to monitor the weather in real time to provide accurate information about the snowfall rate, snow accumulation depth, wind direction, and speed in snowy and/or icy environments. In addition, the snow-TENG can be used as a wearable power source and biomechanical sensor to detect human body motions, which may prove useful for snow-related sports. Unlike conventional sensor platforms, our design works without the need for batteries or image processing systems. We envision these devices could potentially be integrated into solar panels to ensure continuous power supply during snowy weather conditions.

Power supplies for implantable medical devices are often health limiting factors. For example, cardiac pacemakers control abnormal heart rhythms of millions of cardiac arrhythmia patients worldwide, but still suffer from power source limitations. Commercial cardiac pacemakers are battery powered and must be replaced when the battery is low (after 5-8 years). This exposes the patient to pain, serious risk of infection, and the cost of surgery. In addition, battery materials and electrolytes are toxic and raise safety concerns related to possible leakage due to accident or manufacturing flaws. Moreover, batteries represent 50-75% of pacemaker size and limit further miniaturization of the device. We are developing a miniaturized power source called BioSuperCap-Harvest based on technology that provides a smaller, safer, and much longer life-span power to cardiac pacemakers compared to currently existing batteries. The device consists of two stacked ultrathin parts. The first is a flexible bio-triboelectric nanogenerator (TENG) that harvests mechanical energy from a patient’s heart beats and converts it into electrical current. The bioSuperCapacitor will rapidly store the TENG-harvested electrical energy to power devices such as cardiac pacemakers potentially for a patient’s full life-time. The ultrathin 1 cm2 device features graphene layers intercalated with heme proteins in layer-by-layer assembled films. Symmetric supercapacitors using this configuration give outstanding volumetric capacitance up to 849 F cm-3. The supercapacitors also functioned effectively in calf serum, physiological buffered saline and artificial urine as electrolytes with almost no degradation in capacitance after 5000 cycles. They were no toxic effects to cell cultures exposed to over 90,000 charge-discharge cycles while using the cell growth medium as electrolyte. We are currently interfacing this supercapacitor with the triboelectric nanogenerator and will discuss electrical characteristics of the interfaced system.

The development of wearable, all-in-one sensors that can simultaneously monitor several hazard conditions in a real-time fashion imposes the emergent requirement for a smart and stretchable hazard avoidance sensing platform that is stretchable and skin-like. Multifunctional sensors with these features are problematic and challenging to accomplish. In this context, a multimodal ferrofluid-based triboelectric nanogenerator (FO-TENG), featuring sensing capabilities to a variety of hazard stimulus such as a strong magnetic field, noise level, and falling or drowning is reported. The FO-TENG consists of a deformable elastomer tube filled with a ferrofluid, as a triboelectric layer, surrounded by a patterned copper wire, as an electrode, endowing the FO-TENG with excellent waterproof ability, conformability, and stretchability (up to 300%). In addition, The FO-TENG is highly flexible and sustains structural integrity and detection capability under repetitive deformations, including bending and twisting. This FO-TENG represents a smart multifaceted sensing platform that has a unique capacity in diverse applications including hazard preventive wearables, and remote healthcare monitoring.