Problem Statement:

Use of simple spray-coating technique and developed soft-patterning eliminates the use of sophisticated expensive equipment that are required for nanoparticle deposition and microfabrication i.e. simple, cost-effective and time saving process. In addition, spraying and transferring in desired fashion results in development of novel devices with much better efficiency than any other similar device fabricated by another method.

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Detail:

Energy conversion and storage devices are fabricated by spray-coating which is a novel technique for substrate independent fabrication of Nano systems. The technique combined with wet-transfer process allows assembling of the materials in a desired fashion so that the favorable mechanism can be obtained. Most importantly the scalability is easily achieved to obtain highly efficient systems.

Knowledge Provider / Innovator: Sukanta NandiDr. Buddha deka boruah
Address: Sukanta Nandi C/O- Prof. Abha Misra Department of Instrumentation and Applied Physics Indian Institute of Science Near Yeshwantpur Circle/Malleswaram 18th Cross Bangalore – 560012 Karnataka, INDIA
City: Bangalore
State: Karnataka
PIN Code 560012

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Email: sukantamnsl14@gmail.com
Contact No: 9632140802.0

Link: Microfabrication-less fabrication of microdevices using spray deposition of nanomaterials is a much faster and efficient approach by printing the devices on any favorable substrate from metals to polymers at ambient conditions. In addition, our innovation also leads to improvement in device performances compared to conventional techniques. The basic unique features and advantages/achievements of our innovation are listed below-  Spray painted microsupercapacitor: For energy storage application i.e. in case of supercapacitors, novel devices can be fabricated with further high and improved efficiency. In one of our work, (ACS Appl. Mater. Interfaces 2018, 10, 15864−15872) we found that layer-by-layer assembly of three different nanoparticles using spray coating (manganese dioxide, carbon nanotubes and reduced graphene oxide) in a very specific pattern i.e. layered microsupercapacitor (LMSC) resulted in an areal capacitance of ~1.51 times (scan rate of 50 mV/s) compared to that of randomly oriented i.e. random microsupercapacitor (RMSC) with the same amount of active material. The reason being that the LMSC provides faster electrolyte ions diffusion due to increased electrochemical surface area, low charge transfer resistance, and good cation intercalation all these resulting from the adopted sprayed coating device fabrication technique and thus resulting in an enhanced capacitive response compared to RMSC. Further, we could also fabricate array of such improved MSCs on a large standard flexible A4 lightweight polymer sheet (Polyethylene terephthalate). The robustness of the MSCs was also verified under bending conditions and in spite of such bent structure no decrement was observed in the device electrochemical response. In our other work (ACS Appl. Energy Mater. 2018, 1, 1567−1574) the energy storage performance of reduced graphene oxide and vanadium oxide (rGO-V2O5) heterostructure was greatly altered by tuning the device architecture for the same amount of active material using the spray coating technique. Layer-by-layer assembly of rGO-V2O5 using spray coating in the form of interdigitated electrodes i.e. porous supercapacitor (PSC) resulted in an areal capacitance of ~2.2 times (at a current density of ~0.222 mA/cm2) compared to that of conventional supercapacitor (CSC) also fabricated using spray coating. Furthermore, an outstanding stable electrochemical response was also observed towards mechanical deformation. Thus, spray coating not only helps in depositing nanomaterials but also provides the platform for developing novel electrochemical devices by empowering us to manipulate the charge and mass transport. Moreover, spray painting using a single spray coater for a wide variety of multiple nanomaterials in specific patterns illustrated here also gives an upper hand compared to the bulk 3-D printing that in most cases are very specific only to single nanomaterial inks.  Spray painted microphotodetector: For energy conversion application, infrared microphotodetector was also fabricated where we could utilize the wet-transfer technique to transfer multiwalled carbon nanotubes (CNTs) films on micron scale and freestanding films (i.e. without substrate) on trenches ~2-3 micron wide and ~500 nm deep could be successfully transferred and its photodetection properties and bolometric properties were evaluated. An appreciable temperature coefficient of resistance of ~ -0.32 %/K at around 315 K and a resistance change of ~500 ohms was observed. Conventional techniques like dielectrophoresis or drop-casting are used to transfer/bridge CNTs in between the metal contacts but there are problems associated with these techniques. Like for e.g. in dielectrophoresis, bridging of CNTs in between two metal contacts are done under extreme conditions by applying an alternating current of ~500 kHz frequency and electric field of approximately 1000000 V/m, whereas, in our case, by simply wet-transferring we can bridge CNTs in between two metal contacts. Further, in case of drop-casting nanomaterial spreads randomly with great film roughness and increased interparticle scattering that further causes decremental effects to the electrical device performance. Moreover, we cannot get freestanding films using drop-casting. We are able to solve this problem by being able to cut the spray coated nanomaterials deposited on Cu substrate in the desired shape, size and dimension and then later transferring them as required.
Problem Scale: Worldwide