Daniel Ruben Soto

Columbia University | CU · Earth Institute

1.3 Billion people will remain without electricity without significant investment in new energy services. The IEA shows that about half of these services need to be distributed energy to reach those beyond the grid. Current investment focuses on centralized power plants and grid expansion. In the absence of public funding, the unelectrified rural p...

For many isolated regions in the developing world micro-grids which combine photovoltaic electricity generation and battery storage may represent the most reliable and least expensive form of energy service. Due to climate induced solar resource variations, achieving high reliability levels necessitates excess generation and storage capacity which...

Reaching unelectrified populations in the developing world with distributed solar requires agressive cost optimization of generation and storage. Conventional solar generation architectures using photovoltaic panels, sealed lead acid batteries, and inverters show room for cost improvement. Using data collected from photovoltaic microgrid users and...

In this paper we describe the motivations and design process for our open-source, low-power, and high-accuracy AC power meters suitable for several different off-grid metering applications. The described metering and switching hardware is more power efficient than off-the-shelf systems with equivalent capability while being able to measure much sma...

This paper demonstrates a model for electricity delivery and revenue collection in a rural context with the potential to increase the reliability of service delivery and lower operating costs compared to traditional fixed monthly fee utilities. The microutility in this paper provides power on a pre-paid basis similar to the way cellular phone air-t...

We investigated the effects of orientation angle on the adhesion of single gecko setae using dual-axis microelectromechanical systems force sensors to simultaneously detect normal and shear force components. Adhesion was highly sensitive to the pitch angle between the substrate and the seta's stalk. Maximum lateral adhesive force was observed with...

Research into the gecko’s adhesive system revealed a unique architecture for adhesives using tiny hairs. By using a stiff material (β-keratin) to create a highly structured adhesive, the gecko’s system demonstrates properties not seen in traditional pressure-sensitive adhesives which use a soft, unstructured planar layer. In contrast to pressure se...

Geckos owe their remarkable stickiness to millions of dry, hard setae on their toes. In this study, we discovered that gecko setae stick more strongly the faster they slide, and do not wear out after 30,000 cycles. This is surprising because friction between dry, hard, macroscopic materials typically decreases at the onset of sliding, and as veloci...

Prior research in biology and mechanics has shown the importance of hierarchy to the performance of dry adhesive systems on rough surfaces. The gecko utilizes several levels of hierarchy that operate on length scales from millimeters to 100s of nanometers in order to maneuver on smooth and rough vertical surfaces ranging from glass to rock. The gec...

Gecko adhesion has become a paradigmatic example of bio-inspired engineering, yet among the many gecko-like synthetic adhesives (GSAs), truly gecko-like performance remains elusive. Many GSAs have previously demonstrated one or two features of the gecko adhesive. We present a new wedge-shaped GSA that exhibits several gecko-like properties simultan...

A dual-axis piezoresistive MEMS force sensor was used to investigate the role of orientation angle on the adhesion of gecko hairs, called setae. Made of keratin with nanoscale features, gecko setae are a spectacular, robust dry adhesive with anisotropic adhesion properties. A wealth of recent research has been devoted to synthetic mimicry of the ge...

A dual-axis piezoresistive MEMS force sensor was used to investigate the role of orientation angle on the adhesion of gecko hairs, called setae. Previous work showed that the lateral adhesion force of a single seta pulled parallel to a surface is highly dependant upon the "pitch" angle between the seta's stalk and the substrate (K. Autumn et al., 2...