Wearable sensors have recently seen a large increase in both research and commercialization. However, success in wearable sensors has been a mix of both progress and setbacks. Most of commercial progress has been in smart adaptation of existing mechanical, electrical and optical methods of measuring the body. This adaptation has involved innovations in how to miniaturize sensing technologies, how to make them conformal and flexible, and in the development of companion software that increases the value of the measured data. However, chemical sensing modalities have experienced greater challenges in commercial adoption, especially for non-invasive chemical sensors. There have also been significant challenges in making significant fundamental improvements to existing mechanical, electrical, and optical sensing modalities, especially in improving their specificity of detection. Many of these challenges can be understood by appreciating the body's surface (skin) as more of an information barrier than as an information source. With a deeper understanding of the fundamental challenges faced for wearable sensors and of the state-of-the-art for wearable sensor technology, the roadmap becomes clearer for creating the next generation of innovations and breakthroughs.

Controllable biaxial and uniaxial nanowrinkles (see figure) are fabricated by a simple two‐step approach — metal deposition and subsequent heating — based on shape memory polymer (prestressed polystyrene) sheets. The wavelengths of the wrinkles can be tuned by controlling the thickness of deposited metal. The ready integration of the nanowrinkles into microchannels and their effectiveness in surface enhanced sensing is demonstrated.

Increasing the cell membrane's permeability can be accomplished via single cell electroporation. Polar substances that cannot otherwise permeate the plasma membrane (such as dyes, drugs, DNA, proteins, peptides, and amino acids) can thus be introduced into the cell. We developed a polymeric chip that can selectively immobilize and locally electroporate single cells. This easy-to-use chip focuses the electric field, eliminating the need to manipulate electrodes or glass pipettes. Moreover, this device allows parallel single cell electroporation. We demonstrate the effectiveness of our device design by electroporating HeLa cells using low applied voltages (< 1 V). We found the average transmembrane potential required for electroporation of HeLa cells to be 0.51 +/- 0.13 V. Membrane permeation is assessed electrically by measuring characteristic 'jumps' in current that correspond to drops in cell resistance, and microscopically by recording either the escape of cytoplasmic dye Calcein AM or the entrance of Trypan blue stain.

We present a rapid and non-photolithographic approach to microfluidic pattern generation by leveraging the inherent shrinkage properties of biaxially oriented polystyrene thermoplastic sheets. This novel approach yields channels deep enough for mammalian cell assays, with demonstrated heights up to 80 mm. Moreover, we can consistently and easily achieve rounded channels, multi-height channels, and channels as thin as 65 mm in width. Finally, we demonstrate the utility of this simple microfabrication approach by fabricating a functional gradient generator. The whole process-from device design conception to working device-can be completed within minutes.