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Abstract
The development of wearable sensors is aimed at enabling continuous real-time health monitoring, which leads to timely and precise diagnosis anytime and anywhere. Unlike conventional wearable sensors that are somewhat bulky, rigid, and planar, research for next-generation wearable sensors has been focused on establishing fully-wearable systems. To attain such excellent wearability while providing accurate and reliable measurements, fabrication strategies should include (1) proper choices of materials and structural designs, (2) constructing efficient wireless power and data transmission systems, and (3) developing highly-integrated sensing systems. Herein, we discuss recent advances in wearable devices for non-invasive sensing, with focuses on materials design, nano/microfabrication, sensors, wireless technologies, and the integration of those.
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Lay CL, Koh CSL, Lee YH, Phan-Quang GC, Sim HYF, Leong SX, Han X, Phang IY, Ling XY. Two-Photon-Assisted Polymerization and Reduction: Emerging Formulations and Applications. ACS APPLIED MATERIALS & INTERFACES 2020; 12:10061-10079. [PMID: 32040295 DOI: 10.1021/acsami.9b20911] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Two-photon lithography (TPL) is an emerging approach to fabricate complex multifunctional micro/nanostructures. This is because TPL can easily develop various 2D and 3D structures on a variety of surfaces, and there has been a rapidly expanding pool of processable photoresists to create different materials. However, challenges in developing two-photon processable photoresists currently impede progress in TPL. In this review, we critically discuss the importance of photoresist formulation in TPL. We begin by evaluating the commercial photoresists to design micro/nanostructures for promising applications in anti-counterfeiting, superomniphobicity, and micromachines with movable parts. Next, we discuss emerging hydrogel/organogel photoresists, focusing on customizing photoresist formulations to fabricate reconfigurable structures that can respond to changes in local pH, solvent, and temperature. We also review the development of metal salt-based photoresists for direct metal writing, whereby various formulations have been developed to enable applications in online sensing, catalysis, and electronics. Finally, we provide a critical outlook and highlight various outstanding challenges in formulating processable photoresists for TPL.
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Affiliation(s)
- Chee Leng Lay
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634, Singapore
| | - Charlynn Sher Lin Koh
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Yih Hong Lee
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Gia Chuong Phan-Quang
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Howard Yi Fan Sim
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Shi Xuan Leong
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Xuemei Han
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - In Yee Phang
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634, Singapore
| | - Xing Yi Ling
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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Rubio-Lara JA, Bergler F, Attwood SJ, Edwardson JM, Welland ME. Ultraflat Gold QCM Electrodes Fabricated with Pressure-Forming Template Stripping for Protein Studies at the Nanoscale. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:8889-8895. [PMID: 30857390 DOI: 10.1021/acs.langmuir.8b03782] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Single-molecule imaging of proteins using atomic force microscopy (AFM) is crucially dependent on protein attachment to ultraflat substrates. The template-stripping (TS) technique, which can be used to create large areas of atomically flat gold, has been used to great effect for this purpose. However, this approach requires an epoxy, which can swell in solution, causing surface roughening and substantially increasing the thickness of any sample, preventing its use on acoustic resonators in liquid. Diffusion bonding techniques should circumvent this problem but cannot be used on samples containing patterned features with mismatched heights because of cracking and poor transfer. Here, we describe a new technique called pressure-forming TS (PTS), which permits an ultraflat (0.35 ± 0.05 nm root-mean-square roughness) layer of gold to be transferred to the surface of a patterned substrate at low temperature and pressure. We demonstrate this technique by modifying a quartz crystal microbalance (QCM) sensor to contain an ultraflat gold surface. Standard QCM chips have substantial roughness, preventing AFM imaging of proteins on the surface after measurement. With our approach, there is no need to run samples in parallel: the modified QCM chip is flat enough to permit high-contrast AFM imaging after adsorption studies have been conducted. The PTS-QCM chips are then used to demonstrate adsorption of bovine serum albumin in comparison to rough QCM chips. The ability to attach thin layers of ultraflat metals to surfaces of heterogeneous nature without epoxy will have many applications in diverse fields where there is a requirement to observe nanoscale phenomena with multiple techniques, including surface and interfacial science, optics, and biosensing.
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Affiliation(s)
- Juan A Rubio-Lara
- Nanoscience Centre , University of Cambridge , 11 JJ Thomson Avenue , Cambridge CB3 0FF , U.K
| | - Frederik Bergler
- Department of Pharmacology , University of Cambridge , Tennis Court Road , Cambridge CB2 1PD , U.K
| | - Simon J Attwood
- Nanoscience Centre , University of Cambridge , 11 JJ Thomson Avenue , Cambridge CB3 0FF , U.K
| | - J Michael Edwardson
- Department of Pharmacology , University of Cambridge , Tennis Court Road , Cambridge CB2 1PD , U.K
| | - Mark E Welland
- Nanoscience Centre , University of Cambridge , 11 JJ Thomson Avenue , Cambridge CB3 0FF , U.K
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Tan EK, Au YZ, Moghaddam GK, Occhipinti LG, Lowe CR. Towards Closed-Loop Integration of Point-of-Care Technologies. Trends Biotechnol 2019; 37:775-788. [DOI: 10.1016/j.tibtech.2018.12.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 12/11/2018] [Accepted: 12/12/2018] [Indexed: 12/21/2022]
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